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Signal path wire - is 28g too thin?

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Posted on January 27, 2015 at 12:02:17
banpuku
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 I have some OCC copper 28g wire. I was thinking of using it for my signal path wire in my power amp (Lafayette KT-550). Is the 28g too thin? I once read where Allen Wright (Vacuum State fame) said to use very thin wire.

Thoughts?

 

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It's really simple!, posted on January 27, 2015 at 12:42:51
gusser
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 This is an audio amplifier. Ohm's law is sufficient to select wire size.

Personally I would not use 28awg because it's rather fragile.

24-22awg wire is more than adequate for anything in the amp you list other then perhaps the filament wiring.

Furthermore unless the old wiring insulation is deteriorating, just leave it alone. If the goal here is to improve sound quality by replacing the signal path wiring, you are wasting your time.

 

RE: Signal path wire - is 28g too thin?, posted on January 27, 2015 at 12:50:30
rage
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 I think Allen Wright liked thin solid core silver, right?

 

+1, posted on January 27, 2015 at 12:59:29
Triode_Kingdom
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 But don't forget Gusser, it only takes one inch of bad wire, yada, yada, yada. Don't use it if it's green. :)

 

RE: Signal path wire - is 28g too thin?, posted on January 27, 2015 at 13:19:53
SteveBrown
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 Here you go:

 

RE: Signal path wire - is 28g too thin?, posted on January 27, 2015 at 13:23:09
Lew
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 Like Gusser, I probably would not use it, because of the difficulty with soldering and the fragility of 28ga. But it would otherwise be fine. I'd use the narrowest gauge that I could easily work with.

 

Allen is not the only one who touted thinner is better..., posted on January 27, 2015 at 17:09:57
Lew
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 I got the same advice from Pierre Sprey of Mapleshade many years ago. Funnily enough, Pierre prefers copper over silver. I would guess without knowing for sure that very fine copper wire is more sturdy than silver of similar gauge. It's impossible to know whether it's the power of suggestion, placebo effect, observer bias, or what, but I believe I do hear a difference in favor of very thin solid core, certainly over any stranded wire. I can't say that 28ga solid core sounds any better than 26ga solid core, though. I don't want to start another subjectivist vs objectivist brouhaha here. I totally admit this is all subjective. But I am in good company.

 

Just show us the relevant physics behind it!, posted on January 27, 2015 at 18:07:02
gusser
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 And let's not use the Allen Wright book. Last time I saw excerpts it was all RF theory.

Sorry but that phenomenon does not occur at audio frequencies to any level of audible significance.

As always when we do get some physics and math, it's always from audiophool snake oil sales people and totally irrelevant if you have the background to follow it.

Why can't we get that same information from accredited institutions?

Here you go, this is from Belden, one of the worlds oldest and largest manufacture of communications cable used extensively in broadcast and mastering facilities.

 

"relevant physics"? It is called resistance, posted on January 27, 2015 at 19:03:23
Chip647
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 If you take 12 inches of 28 gage wire and it has 0.02 ohms resistance and you pass 0.1mA of signal, the wire will consume 0.0002 watts. Yippy.

 

RE: "relevant physics"? It is called resistance, posted on January 27, 2015 at 19:14:12
cpotl
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 "If you take 12 inches of 28 gage wire and it has 0.02 ohms resistance and you pass 0.1mA of signal, the wire will consume 0.0002 watts. Yippy."

0.0002 micro-watts. Which makes your point even more strongly!

Chris

 

RE: "relevant physics"? It is called resistance, posted on January 27, 2015 at 19:28:28
Tre'
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 45 volts peak (driver stage feeding output tube) across 250k grid resistor is .18ma

.18ma flowing across .02 ohms gives a .0000036 volt drop.

If we factor in the current needed to drive the Miller capacitance of the output tube the current will go up.

Assuming 3ma. and the voltage drop is .00006 volts.

Tre'


Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Just show us the relevant physics behind it!, posted on January 27, 2015 at 19:35:48
Lew
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 I will be the first (or the second) to admit, there is no freakin' sense to it.
However, Allen and Pierre were/are no fools. Or, use lamp cord for all I care.

I am ok with these discussions, but if my sort of comment about wire is driving away the guys who are really knowledgable in this field, and from whom I come here to learn, then I will desist in posting any observation that is not based on "physics".

 

Wire, posted on January 27, 2015 at 20:32:01
Triode_Kingdom
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 I don't personally believe this is audible in short conductors, but there is more to wire than simple resistance...



 

RE: "relevant physics"? It is called resistance, posted on January 27, 2015 at 22:49:35
danlaudionut
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 >> 12 inches of 28 gage wire and it has 0.02 ohms resistance

But at what frequency?
The resistance is not independant of frequency.
DC resistance and AC resistance may not be equal.
If it is at 1KHz it may not be at 20Hz or 20KHz.

FYI I too am sold on solid core over stranded.

DanL



 

Allen Wright's credentials & accomplishments trump any navel aviation art spewed in this thread-nT, posted on January 28, 2015 at 03:48:00
Cleantimestream
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 !
The Mind has No Firewall~ U.S. Army War College.

 

RE: Allen is not the only one who touted thinner is better..., posted on January 28, 2015 at 04:14:17
morricab
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 Thin foil is even better than thin wire. I had Allen at my place a number of times and we went back and forth between his super thin wire interconnects and flat foil. The foil always made a better sorted soundstage and better bass...simply more 3d in all ways. I use only silver foil now in my interconnects.

I have one set of Allen's wire interconnects and one set of foil but most of my cables are from Goertz, which was more affordable and follows the same philosophy about signal transmission more or less.

 

RE: Signal path wire - is 28g too thin?, posted on January 28, 2015 at 04:52:49
Stephen R
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 I've used wire like that. It will be just fine for signal. I've used a lot of Kimber SF23 which is a bit fatter but it really doesn't matter.

I used magnet wire of that size for long interconnects once with no real issues. After all, you don't hang your washing on it.

If it makes a difference you like, great. Who cares what anyone else says it will do or won't do. It only has to please you. You really don't need to produce a white paper to please other people when wiring up your own amp.

Pay attention to it's voltage breakdown if it passes by some high voltage bits and it's insulation mechanical strength might be an issue if it flaps about.

cheers,

Stephen

 

And sometimes right into a 1000 ohm grid stop resistor (nt), posted on January 28, 2015 at 04:53:53
Chip647
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Thanks, TK, posted on January 28, 2015 at 06:28:05
Lew
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 I have never seen those data, but I did recall before now that the rationale for the putative superiority of very thin, solid core wire for carrying audio signal was based by some on "skin effect". However, back in the day when audio magazines published science-based articles now and then, I think the hypothesis was also denounced by other knowledgable persons.

 

Foil is tough to work with inside a chassis..., posted on January 28, 2015 at 06:29:48
Lew
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 Where do you get yours? Does Vacuum State still sell it?

 

RE: "relevant physics"? It is called resistance, posted on January 28, 2015 at 06:41:13
cpotl
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 ">> 12 inches of 28 gage wire and it has 0.02 ohms resistance

But at what frequency?
The resistance is not independant of frequency.
DC resistance and AC resistance may not be equal.
If it is at 1KHz it may not be at 20Hz or 20KHz."

True. But the inductance of a 12 inch length of 28 gauge wire is about 0.4 micro Henries, so even at 20 KHz this would represent a reactance of only about 0.05 ohms. This would still be negligible, compared with the input impedance of the stage it was connecting to.

Chris

 

RE: "relevant physics"? It is called resistance, posted on January 28, 2015 at 07:24:23
danlaudionut
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 I am not saying I have all the answers but
I have found various gauge sizes and shapes
definitely changes sound as well as insulation.
Thinner gauges favor higher frequencies.
Thicker gauges favor lower freqencies.
I won't even get into flat/round/square wire.

DanL



 

RE: "relevant physics"? It is called resistance, posted on January 28, 2015 at 07:59:45
cpotl
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 "I am not saying I have all the answers but
I have found various gauge sizes and shapes
definitely changes sound as well as insulation.
Thinner gauges favor higher frequencies.
Thicker gauges favor lower freqencies.
I won't even get into flat/round/square wire."

Well, it is hard to argue with anecdotal reports. All I would say is that with no apparent physical explanation that could plausibly account for the reported differences, and with no measurement data either, one would need to be extremely rigorous in conducting double-blind testing before being able to draw the conclusion that the effects were real. And certainly, before one could convince a skeptical outsider that the effects were real. "Extraordinary claims require extraordinary evidence."

Chris

 

But he was human like the rest of us, posted on January 28, 2015 at 08:11:58
Triode_Kingdom
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 And he made mistakes and had biases like the rest of us, too. Sometimes, people like something just because they do. Despite their credentials, it may not be the best choice for others, particularly when it's based on a subjective or idiosyncratic response.

 

That's true for violin strings!, posted on January 28, 2015 at 08:22:17
gusser
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 But just because a violin and an amplifier both process sound in some fashion, that hardly means the same physical material laws apply.

Just as skin effect plays a major role on your CATV feed, that doesn't mean it's a factor in the performance of your audio interconnects.

 

Do they?, posted on January 28, 2015 at 08:31:01
gusser
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 He has an extensive bio on his WEB page and no where does it mention any formal training in electrical engineering.

In fact it says he started out as a TV test technician on an assembly line then moved to 2way radios. After that he was hired by HP as a service technician. HP, Tektronix, and similar companies will take self taught experience for service positions. But try to get into the engineering department with just that! After that he went into the audiophile hack business.

So no I'm not overly impressed. Tube stuff is simply not that difficult to make work. Note that getting some tube project to process audio is not the same as real electrical engineering.

 

RE: Do they?, posted on January 28, 2015 at 09:15:45
Cleantimestream
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 Amplifiers ARE the simplest circuit.... unfortunately I have heard a lot of kilobuck trash when my homebuilt system soundly trounces 150,000 worth of sound engineering...somebody. you? Are measuring the wrong thing

The Mind has No Firewall~ U.S. Army War College.

 

Absolutly!, posted on January 28, 2015 at 10:27:39
gusser
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 One may wire their amp with what ever they want. No official justification is needed.

However there's noting wrong with pointing out accredited science that says it's not going to improve performance.

Now the OP has heard both sides and may choose his options. before this he may not have heard the opposing view.

 

RE: Do they?, posted on January 28, 2015 at 10:29:57
gusser
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 And it's that kilobuck trash that uses this exotic wire and magic capacitors.

Good amplifiers at residential power levels can easily be found at less then $1000.

 

RE: Allen is not the only one who touted thinner is better..., posted on January 28, 2015 at 10:42:18
gusser
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 Strap conductors are widely used in microwave circuits. Have been for well over 60 years. These days it's all done via PC boards as not only can precise conductors be made, it's highly repeatable for low cost manufacturing.

But all of this is irrelevant for base band audio. The math doesn't lie.

Can you or anyone explain to us how the flat conductor is improving the sound stage or bass response versus a round wire. Keep in mind we are talking a few feet maximum length here and assume the wire in question is over rated current wise by a factor of at least 10, meaning a line level signal over say a 24awg wire.

Just point us to the relevant physics at play here (edit: at aduio frequencies please. We do understand the physics at RF frequencies).

 

RE: Absolutly!, posted on January 28, 2015 at 10:50:07
Stephen R
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 Accredited science may well state the wire won't change gross parameters of performance or basic operation. Fair enough and what I would expect and pretty much know to be the truth based on my experience.

However that doesn't mean there won't be changes that can be observed by other methods. Note changes, not better, not worse. Just an observable difference. This I also know from observation, ABX or whatever from personal experience.

I also know that some people can't hear a difference and others can. But hey, everyone has differenct priorities, sensitivities and experience.

Most times I put these types of differences we're talking about here into the pot of "I can't be arsed". Doesn't mean they don't exist.

 

RE: Absolutly!, posted on January 28, 2015 at 11:02:36
gusser
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 But the observed change may have nothing to do with the physics at play in the wire.

Placebo is an observed phenomenon. So are other mental biases.

I will point out that the world electrical engineering community as a majority does not support these claims. That is evident in countless commercial products. It's only a miniscule group of audiophiles.

 

RE: Foil is tough to work with inside a chassis..., posted on January 28, 2015 at 12:38:54
morricab
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 Got my interconnects maybe 10 years ago when Allen was still with us.

 

RE: Do they?, posted on January 28, 2015 at 12:48:01
morricab
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 "Good amplifiers at residential power levels can easily be found at less then $1000"

Good what? Measuring? Sounding? Please define what YOU mean by good amplifier.

 

Actually, the math..., posted on January 28, 2015 at 13:35:57
Lew
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 does not exactly "lie", but it is generally only a close approximation of reality, because the theories or Laws that give rise to the math of physics are themselves built to describe ideal, isolated systems. However small the errors may be, there are errors. In most cases, we are aware of the sources of those small errors, but not always. Maybe inside that tiny uncharted part of the physical real world is where some of these otherwise inexplicable subjective observations live. Dare I say "Quantum Theory"? No, I don't dare.

 

Come on..., posted on January 28, 2015 at 14:03:36
gusser
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 This is an obsolete tube amplifier design that was retired by the commercial industry over 50 years ago. Yet you want to believe it holds some mysterious property that the evolution of modern electronics has not yet discovered?

I'm not trying to sound belittling, but comments like you just made always seem to come from people lacking higher level scientific educations.

Electronics and physics these days is on the brink of generating our own black holes. Do you really think all the secrets of physics are locked in a DC coupled 2A3 amplifier design from 1931?

 

RE: Come on..., posted on January 28, 2015 at 14:10:23
kyle
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 My education is just fine and still prefer the sound of one these obsolete designs to a mass market sub $1000 amp. For reasons of sound preference and not the engineering behind it, I'll take a good SET any day.
I make my own amps of a wide variety of configurations, I can understand the electrical principals involved and yet I still listen to SETs. Go figure.

 

I'm not disputing that., posted on January 28, 2015 at 14:18:56
gusser
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 You and many others like the sound of vintage SET's. I like vintage 1960s PP amps. But sonically accurate they are not.

And this constant drivel buy a few here to make these hobby projects the second comming is getting ridiculous.

 

RE: Do they?, posted on January 28, 2015 at 14:31:38
gusser
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 This "measures good, sounds bad" thing is a bit dated. That was said by HH Scotts chief engineer in the late 1950s and meant a lot back then with the quality of components and measuring equipment at the time. Could anyone do an FFT back then in real time? Hardly, not even the most sophisticated computers of the day. So we really could not analyze distortion like we do today on our low cost personal computers. Not even close!

My take;

A good amplifier is a piece of wire with gain. And I am hardly the author of that rather old cliche either. But for the past 10 years or more we are practically at that point with class B amplifier design. Now the push is on efficiency and why we see so much going on with class D. Look at the Ncore modules for a high end example.

Tube amps have a unique sound. I like them too and use them for music listening. But sonically accurate they are not.

All the advances in mass transistor fabrication has gotten us to a near perfect amplifier at a commodity cost. We are way past the transistor amps of the early 1970s.

Let's not kid ourselves here. You can buy a $600 Dennon AV receiver at Best Buy today to will measure very well to standard engineering parameters. Now some will say it sounds like crap - right? But what is that claim based on. How does it sound like crap? Does it really or is the Dennon name what you are really listening to?

 

Agreed., posted on January 28, 2015 at 14:38:21
kyle
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 If I want sonically accurate, I have to go to a live performance because no amount of money spent or equipment bought is going to get close.
I hear very few people speak of how wonderful their room treatments are and yet they could get a much larger bang for the buck by getting their room treatments in order. I'm not talking about small stones or stick on dots either. I mean real sound absorption and diffraction in correct proportion. That can do more to improve your at home sound quality than a new pair of $1000 tubes or multiple bypassed caps ever will.
I guess that's off topic because this is tube DIY not the sound quality forum:)

 

"a much larger bang for the buck by getting their room treatments in order" +1, posted on January 28, 2015 at 15:55:07
Tre'
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 .
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Absolutly!, posted on January 28, 2015 at 20:50:12
RC Daniel
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 Yep.

Both positive and negative expectation effects come into play. So often you see people's experiences dismissed because of assumed placebo effects (positive expectation), yet negative effects are conveniently overlooked.

Of course, different people, cultures etc. demonstrate varying degrees of these effects. Interesting stuff.

Then there are Hawthorne and other effects...

Cheers.

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

Not accurate??, posted on January 28, 2015 at 22:30:14
Triode_Kingdom
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 "But sonically accurate they are not. "

This might be one of the few areas where we disagree. Tubes are inherently accurate, particularly triodes. Where they sometimes fail is in the interface to the speaker, but that's a system issue. One need only listen to a good tube amplifier with good headphones to know this is true. No SS amp I've heard (and I've listened to some of the best going back to the '70s) has ever produced the stunning, in-your-face realism that I experience with simple class A pentodes or triodes and good (but not expensive) headphones. If I had a really good set of high-end horns, I'm sure I'd be saying the same thing about tube amps and speakers. You're entitled to your opinion, but it's for the sake of accuracy that I'll never go back to solid state.

 

RE: I'm not disputing that., posted on January 29, 2015 at 02:26:53
morricab
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 "You and many others like the sound of vintage SET's. I like vintage 1960s PP amps. But sonically accurate they are not."

Sonically the ear/brain is far more complex than the oscilloscopes and digital FFT software that you would use to define accurate. Accurate to a meter is not necessarily accurate to a listener. You should acquaint yourself with psychoacoustic studies.

 

RE: Do they?, posted on January 29, 2015 at 02:42:37
morricab
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 "A good amplifier is a piece of wire with gain."

Doesn't exist and probably never will. Given that ALL devices are to one degree or another non-linear then the pattern of distortion that they make IS relevant to the listener. You engineering types will never get this I think. As a scientist, I make observations first then go looking for the reasons. Sure the modern tools help to understand WHAT a product is doing but not how it sounds to a human...this can only be done by correlating the two things to find what produces a given response in the detector (i.e. humans). It is messy and prone to error but it is the ultimate arbiter.

"But for the past 10 years or more we are practic

"practically at that point with class B amplifier design"

Nonsense! Sonically they are not much closer than 30 or 40 years ago AND if they are it is only because of going to Class A bias and reducing or eliminating global and much of the local negative feedback... Pro amps do not deliver high fidelity SOUND...they might produce high fidelity numbers but those numbers are not telling the true story that the listener hears.

"Tube amps have a unique sound. I like them too and use them for music listening. But sonically accurate they are not."

To many ears they sound CLOSER to what is heard live or with a really good recording than other options...this would make them MORE sonically accurate than the alternatives...to the listener...instruments only tell what but not the impact of that what.

"You can buy a $600 Dennon AV receiver at Best Buy today to will measure very well to standard engineering parameters. Now some will say it sounds like crap - right? "

And you know what?? It does sound like crap. I have a friend with just such a device and he hates to listen to my system because it makes his sound so bad...he realizes it but mostly cares about movies for which it is fine.

Another friend (a woman actually) wanted my help to build a home theater system for her and her boyfriend. Now, after we picked speakers they decided they wanted a true high end stereo system instead. After hearing their Denon integrated amp compared to other better options they concluded that their Denon sounded broken...I am sure it measured fine. They were completely non-audiophiles, BTW, but he was a guitar player.

I have no beef against Denon, you could replace that name with whatever and it still going to sound like crap.

Like I said before, Accurate to what? The meter or the listener? One is easy and clear to define and the other is messy and fraught with bias and other challenges but it is the true accurate. I know you want a clean and clear cut solution but has the last 80 years of audio engineering shown that it is anything but a clean solution and that while you think amp design is trivial it is clearly not when the final decider of quality is the listener and not the meter.

 

RE: Not accurate??, posted on January 29, 2015 at 02:45:47
morricab
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 "If I had a really good set of high-end horns, I'm sure I'd be saying the same thing about tube amps and speakers."

I finally did just this (Odeon wood horns) and it is really great sounding! BTW, really good triode amps strapped to big, full range electrostats will get a similar result with just a bit less dynamic pop, however, it might give an even more holographic and realistic perspective at moderate levels.

 

RE: Do they?, posted on January 29, 2015 at 03:40:50
cpotl
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 "I have no beef against Denon, you could replace that name with whatever and it still going to sound like crap."

The thing I never understand about these kinds of assertions about how everything that is solid state "sounds like crap" is that in the entire passage of the audio signal from the microphones in the recording studio through until the output of the home CD player, the signal will have been amplified, mixed and processed using many stages of solid-state amplification. It will probably have been through countless coupling capacitors, of which quite a few are very likely electrolytics, and none of them audiophile paper in oil, or whatever. The signal will have been though all kinds of lengths of EE standard wire, with nothing bespoke at all. And it will very likely have been subjected to huge amounts of negative feedback in the stages along its path.

After all that, then surely if the claims about solid state "sounding like crap" were true, the signal coming out of the CD player would have been so utterly ruined that it was beyond redemption?

And when someone is comparing a solid-state amplifier unfavourably against a vacuum-tube amplifier, surely what they are actually comparing is more like 20 solid-state amplifiers in succession versus 19 solid-state amplifiers and a vacuum-tube amplifier?

Chris

 

and then another part of reality is the unexplained Synergy between components-nT, posted on January 29, 2015 at 03:58:56
Cleantimestream
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 !
The Mind has No Firewall~ U.S. Army War College.

 

RE: Do they?, posted on January 29, 2015 at 05:32:01
morricab
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 Well it is simple really...most recordings sound like crap! Especially rock/pop recordings but also many Jazz and classical recordings. Many sound, ok...until you compare them to a truly great recording...often made with a tube microphone and tube chain (think late 50s jazz for example or RCA Living Stereo recordings).

There was an intersting article from the early 70s regarding the degradation in sound quality of recordings that the authors had primarily traced to the replacement of tube gear with SS gear in many studios.

 

"most recordings sound like crap!", posted on January 29, 2015 at 05:46:08
Triode_Kingdom
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 Yes, and what you said about the decline in quality during the changeover phase is true as well. The SS sound seems particularly noticeable on albums from the late '60s through mid '70s, which unfortunately includes some of my favorite artists.

 

RE: Do they?, posted on January 29, 2015 at 06:13:54
cpotl
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 "Well it is simple really...most recordings sound like crap! "

Yes, but if it were really true that "all SS equipment sounds like crap" then it would have to be true that *every* CD, without exception, would sound like crap. I don't suppose anyone really claims that?

And even with the old vinyl recordings, made with tube equipment, the signal will have been through umpteen coupling capacitors on its route to the home record player. Where does that leave the people who claim that every coupling capacitor sounds like crap?

"There was an intersting article from the early 70s regarding the degradation in sound quality of recordings that the authors had primarily traced to the replacement of tube gear with SS gear in many studios."

I think it is generally agreed that back in the early SS days, as late as the early 70s, SS amplification had not been properly mastered. So an article from the early 70s making that comparison is not likely to be particularly relevant to the present day.

It seems to me that there is a far simpler and more economical explanation available that accounts for why some people find the sound of a vacuum tube amplifier more pleasing, despite the previous umpteen stages of amplification and processing having been solid state. Namely, that the vacuum tube amplifier is *adding* a particular colouration to the sound, that people find pleasing to the ear.

It seems much more plausible than the alternative explantion implicitly adopted by some people, which would somehow have to be that "crap to the nineteenth power" is much nicer than "crap to the 20th power."

Chris

 

RE: Do they?, posted on January 29, 2015 at 06:42:47
gusser
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 "There was an intersting article from the early 70s regarding the degradation in sound quality of recordings that the authors had primarily traced to the replacement of tube gear with SS gear in many studios."

Yes, the solid state technology in the late 60s through the 70s was rather poor.

But it's not today.

 

RE: Do they?, posted on January 29, 2015 at 07:11:49
RPMac
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 "that people find pleasing to the ear" vs. what measures good/correctly
Isn't this the basis for most of the debates here?

My last solid state amp was a stasis amp(a Nelson Pass design). I've lived with the same speakers and basically the same source since the early 1980's. The longer I listened to the stasis amp, I wanted to turn it down.
The longer I listen to my BottleHead amps, the more I turn it up.
It's that simple.

For some, this hobby is about the music and building by the book that measures good becomes secondary to how it sounds.

 

Whoa!, posted on January 29, 2015 at 07:32:54
Lew
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 I was not speaking to this amplifier design. I was making a general statement in response to your general statement that "math does not lie". I am not a proponent of any amplifier design. (In fact, I don't even know exactly what amplifier you are thinking of.)

 

RE: Not accurate??, posted on January 29, 2015 at 07:50:37
gusser
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 Well you know what I mean. I'm talking about the Magnavox console sound, you know, the classic liquid bass.

I realize with care you can make very good tube amps. But even then I think there is still some slight coloration which does sound good to most people including me.

I run a tube amp music system and formally ran an all tube 5.1 HT system for six years. I just got tired of the maintenance on the 5.1 system.

 

RE: Whoa!, posted on January 29, 2015 at 07:57:17
gusser
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 "I was not speaking to this amplifier design. I was making a general statement in response to your general statement that "math does not lie". I am not a proponent of any amplifier design. (In fact, I don't even know exactly what amplifier you are thinking of.)"

Well in that respect you are most correct. Calculus is by it's nature an approximation, not an exact.

 

RE: Do they?, posted on January 29, 2015 at 08:04:22
gusser
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 I built the classic Pass amp a few years ago. Was not all that impressed. Then I tried a class B amp design running hard in class A, similar to the ESP designs. Much better.

I know the "less is better" idea is very popular in high performance audio. The SET is a great example. But I have always found in my work with audio amps that the extra components some feel compromise a design really do offer an improvement.

Few will argue a current sink in the tail of a tube diff amp phase splitter makes a considerable improvement in distortion. The reasonthis was not done in 1960 was technology. But still I remember there was one tube amp that did use a tube current sink.

 

RE: Foil is tough to work with inside a chassis..., posted on January 29, 2015 at 09:46:59
Lew
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 I thought you were referring to chassis wire. Allen did also advocate using his silver ribbon wire in circuit connections. In fact, I think VS used to sell it.

 

RE: Absolutly!, posted on January 29, 2015 at 10:10:14
Stephen R
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 I don't disagree with what you say.

All I'm saying is that for some, there is a very real difference. One that can be identified in a manner that means there was no placebo or other mental issues.

Some of the differences are small. If I can't be bothered, some of the differences become inaudible to me. If I really care and put some effort in, then some of these differences are there.

I don't see what the issue here is. If this was visual identification of some aspects of an image, there would be no problem. I am rubbish at visual stuff but pretty good with audible stuff.

I wonder why that could be? Education is where it's at.

 

RE: Do they?, posted on January 29, 2015 at 10:50:36
kyle
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 Gusser, when you say class B amp, do you mean an amp running in class B or AB? In either case, how do you run a class B or AB in class A?
Thanks.

 

RE: Do they?, posted on January 29, 2015 at 11:36:24
gusser
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 A class B amp modified for class A bias.

 

RE: Do they?, posted on January 29, 2015 at 11:58:40
kyle
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 Maybe I have a different definition of class B. The ESP site lists the NAD 3020, Cyrus 1 and Sugden A48-II as class B amps but from my perspective these are all class AB as the output devices don't completely switch off at the zero crossing as in a typical class B design. Is that how you interpret it or have I missed something?

 

RE: Foil is tough to work with inside a chassis..., posted on January 29, 2015 at 12:52:27
morricab
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 I borrowed his 300B monos for a while...all silver foil wired inside...must have been a bitch to do. They sure did sound good with the STAX ELSF81s I had at the time...didn't play really loud but it was OMG transparent and tonally amazing.

I saw that the Ancient Audio Grand monos (parallel 300Bs) also use silver foil everywhere inside.

 

RE: Do they?, posted on January 29, 2015 at 13:04:11
morricab
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 I will cut to the chase with you, shall I? I have done extensive comparisons with what are considered to be the best SS amps on the market as well as with multiple Class D, tube, hybrids etc. SS is smoother and less grainy than from the past...but arguably even less interesting to listen to because the life, which was there occasionally in the older SS designs, is gone gone gone in most of the newest ones.

Which kinds of SS amps? McInstosh (newer ones not old ones), Musical Fidelity KW series, Krell (various models from old to newish), darTZeel, Soulution, Spectral, Moon, Halcro etc. Most sound pretty smooth, even a bit warm at times but none has the life I hear from the best tube amps. Ever heard a Halcro that was all the rage about 10 years ago?? Dreadful stuff but measured better than anything else on the planet...literally.

I currently have two amps: one is pure SET the other is a single ended hybrid with that uses a single big MOSFET on the output in Class A. They sound fairly different from each other but both have high resolution and great tonality. Where they differ is in the presentation of the stereo soundstage and image field and in bass quality. The hybrid has a distinct SS tight dry bass whereas the bass on the SET is actually tight but not as dry...it has very good output iron. It also has a bit more of that inner "life" maybe its just how the darn transistors deliver the signal...not sure but you can hear it...maybe it is the lack of output iron...but it doesn't sound like an OTL either (had two different models of those as well).

I suggest you do some reading about the effect design has on perception of sound rather than raw numbers, which only tell what something is but not the impact of what it does. I would argue that feedback doesn't so much suppress or eliminate distortion as it simply shifts it around (read the white paper from Nelson Pass and some of Norman Crowhurst's writings about signal modulated noise floors created by feedback).

 

Have you heard any recordings that sound like the real thing?, posted on January 29, 2015 at 13:10:55
morricab
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 1) I never said ALL SS gear sounds like crap. Just most of it. I even have a hybrid amp...admittedly it is a Single ended hybrid so only the output is SS (and only 1 transistor at that) in Class A with no feedback. I have had other hybrids that sounded quite good as well. Even had a BAT VK200 for a while that wasn't half bad. Small signal transistor products, like a microphone preamp, fair somewhat better but they are more easily overloaded than a tube microphone preamp and still sound less full like the live performance.

I haven't...except a few direct cut disks that were pretty close and some R2R recordings I made myself through a tube mic preamp (yes the tape deck had transistors).

I can see you won't be persuaded by a logical argument so I will stop by saying read up on the psychoacoustics of the matter and you will see that it is not as simple as you think. Also, this article from the 70s made an interesting point that they saw the most damage occurring where the electronics interface with an acoustic transducer (microphone to mic preamp and amp to speakers).

 

RE: Do they?, posted on January 29, 2015 at 13:14:38
morricab
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 "I know the "less is better" idea is very popular in high performance audio. The SET is a great example."

It is popular to characterize SET as less but that is only as far as the actual amplification circuit. The power supplies in the best are quite complex and of course there has to be far greater care in the choice of passive parts. Some go to the extreme of making their own caps, transformers and resistors...so less circuit but more in terms of what goes into the amp itself.

 

Reading:, posted on January 29, 2015 at 14:34:55
gusser
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 Well as for reading I am a big fan of Douglass Self for solid state amps and Morgan Jones for tube amps.

Self has identified some very interesting distortions like from speaker protection relays. And he has documented proof as well. Not a big deal design wise but it shows how good the resolution of modern test gear as well as solid state amp design. I mean if you can separate out the minuscule distortion from relay contacts, the rest of the amp must be damn good in that respect.

 

I don't get that., posted on January 29, 2015 at 14:48:52
gusser
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 That being the idea that an SET has more critical component quality needs than a PP amp? A bad cap is a bad cap for example.

Are you saying the SET amp being simpler electrically is more transparent and therefore more does not mask the failings of poor components? That is a popular audiophile theory btw.

But it doesn't make any sense. A good PP amp has much lower measured distortion than an SET. So it would seem the PP amp would be far more critical of bad components than an SET.

This old idea that the simpler an active circuit the less it colors the signal is flawed audiophile logic. All active electronic components and some passive have non-linear operating areas. Using additional components to correct that non-linearity improves the signal fidelity and adds less distortion to the path. There's a balance though. Noise for example is an enemy here.

It is the advance of electronics knowledge that got us to more complex amplifier circuits. And what drove that advancement is the quest for better and better quality. So IMO, this idea that the pinnacle of amplifier design was the 1930 SET is ludicrous.

How many recording studio are using SET amps or the solid state single transistor version? I know there might be one or two small shops but lets face it, this is long dead technology in the professional world.

 

RE: Have you heard any recordings that sound like the real thing?, posted on January 29, 2015 at 18:20:04
cpotl
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 "I can see you won't be persuaded by a logical argument so I will stop by saying read up on the psychoacoustics of the matter and you will see that it is not as simple as you think."

It's not really a question of logical arguments here. You are reporting that you have a preference for the sound from a vacuum tube amplifier. There is no problem, or contradiction here, with what I am saying. I don't doubt you at all. Psychoacoustics might well be relevant for explaining *why* you prefer the sound of the vacuum-tube amplifier. But that is not my point.

I am simply making the point that when we listen to a CD, we are listening to a musical rendition that has come primarily through solid-state amplifiers. This, I think, is indisputable. At the end of the chain, the home listener in his living room has the option of using a final stage that is either solid state or vacuum tube. If someone finds the vacuum-tube amplifier produces a more appealing sound, then the most economical and most plausible explanation for this is that this (N+1)'th stage in the process is *adding* a sound quality they like, rather than that it is not adding an (N+1)'th stage of crapiness to the N previous stages of solid-state crapiness.

In other words, the fact that some people report that a vacuum-tube amplifier makes for a better sound, when playing CDs, strongly suggests that they like a specific colouration that the vacuum-tube amplifier adds to the audio signal. This is a perfectly reasonable, and consistent possibility. It is also completely consistent with the hypothesis that the many solid-state stages on the route to the output of the CD player (modern technology, not early 1970s SS technology) are essentially reproducing "uncoloured" audio signals.

Chris

 

RE: Reading:, posted on January 30, 2015 at 02:27:49
morricab
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 "Self has identified some very interesting distortions like from speaker protection relays."

That's nice, now do you know if it has an actual sonic impact to a listener or is it just another number?

"I mean if you can separate out the minuscule distortion from relay contacts, the rest of the amp must be damn good in that respect.
"
Perhaps but it can still sound like crap to an experienced listener.

Seriously, you can throw all the engineering you want at me and I don't disagree with you in the sense that many of these things are measurable. Most in fact. BUT and it is the BUT, if you don't correlate it back to the listening experience then you have just performed an exercise in navel gazing.

I have the same issues in my work. I develop drug products for a major pharma company. We have specs for those drugs technical performance just like the specs for an amp. Mostly though, they are for quality control because nearly all of them have NOTHING to do with how that drug works or doesn't work in your body. That is why we have to do clinical trials because all the technical data in the world will not tell you if it is beneficial or not to the patient until you actually put it into the patient.

THEN you can start to see if you have correlations between the clinical effect, which is a VERY noisy signal and why so many people and trials must be conducted, and some technical data (like rate of dissolution) that is relatively controlled and has a high S/N. However, usually the technical test must be heavily modified to a particular system to get meaningful data in terms of correlation.

The point of my story is that all the technical data that you like to discuss and ask for proof is meaningless on it's own for determining sound quality. Its that simple and I can't help you if you don't understand this basic philosophical concept. It is useful on its own to tell if one unit out of a production line is faulty...QC in other words but that's it. Once you can correlate with what listeners find more realistic then you are getting somewhere and discussion of relay distortions or capacitor distortions or feedback distortions becomes interesting.

This is a SCIENTIFIC perspective not an engineering perspective. I and others want to make better SOUNDING gear...not better measuring gear per se (only if the decisions that get better measurements leads also to better sound). If it measures good and sounds bad then there is a flaw in the ENGINEERING concept chosen as a solution to eliminating distortion. The scientific perspective is to point out that the engineering solution does not lead to the desired output...good sound. Once engineering steers towards this concept then better sounding products will emerge (many are going this way even if it appears they are using "obsolete" techniques).

 

RE: I don't get that., posted on January 30, 2015 at 02:32:54
morricab
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 "But it doesn't make any sense. A good PP amp has much lower measured distortion than an SET. So it would seem the PP amp would be far more critical of bad components than an SET.
"

You have to ask yourself WHY does a PP amp have much lower distortion...it is only through the use of a lot of feedback. Remove the loop and you will get MUCH higher distortion...I don't think this aspect has been properly explored as to it's sonic implications...although Cheever did some work in this regard.

"This old idea that the simpler an active circuit the less it colors the signal is flawed audiophile logic. All active electronic components and some passive have non-linear operating areas. Using additional components to correct that non-linearity improves the signal fidelity and adds less distortion to the path"

This is simply false. It is only by wrapping it in feedback that you get that result. A multistage amplifier without feedback will have very high distortion. Adding more non-linear components gets a more and more non-linear system...to think otherwise is silly.

"How many recording studio are using SET amps or the solid state single transistor version? "

Irrelevant because they are drinking the orthodoxy coolaid.

 

Feedback is bad? Dig deeper!, posted on January 30, 2015 at 11:30:26
gusser
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 "This is simply false. It is only by wrapping it in feedback that you get that result. A multistage amplifier without feedback will have very high distortion. Adding more non-linear components gets a more and more non-linear system...to think otherwise is silly."

Well is adding a feedback circuit not the same as "adding additional components to correct a non-linearity"? It sure is!

This negative view of feedback is spread by these audiophile rags written by sales people. Any trained EE knows the power of feedback if applied properly and that extends to many other engineering disciplines as well. Cruise control, autopilot, these too are feedback systems and the exact same rules of math and physics apply. I know, I studied servo design!

The whole feedback smear campaign actually started with Matti Otala in the mid 1970s. But the contributions of his work are largely unknown and/or misunderstood by the audiophile community. Most audiophiles jump on the old time travel paradox where you can't correct a signal that has already passed through the amplifier. And that is quite correct and a real problem with wide band amplifier design like analog video.

But the time travel problem is totally irrelevant to audio amplifiers!

Simply put, no musical instrument can produce a rise time fast enough in our 15psi atmosphere to induce the popular audio amp feedback problem myth. An audio signal is many magnitudes slower than the propagation delay of the amplifier circuit. This whole leading edge distortion theory with audio amp feedback simply does not occur with music. You can easily produce the fault with a simple square wave generator but real music, speech, and sound effects cannot.

What Matti Otala really did was to bring about the focus on amplifier stability. While the feedback loop can correct non-linearity very well in an audio amplifier, if not properly compensated it will enhance instability. And it is/was that ringing and aggravated instability that produced the unpleasant 70s transistor sound as well as the destructive runaway oscillation which destroyed may amplifiers and speakers. Early solid state designs piled on huge amounts of feedback because they were finally freed from the limitation of the tube OPT phase shift. Yes they overlooked the stability issue in greater detail.

Feedback in audio amplifiers is a godsend if properly managed. And today due to the contributions of enginerrs like Matti Otala we now know how to do that.

 

Apples and oranges, posted on January 30, 2015 at 11:50:10
gusser
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 The medical industry still has vast unknowns. There have been great advancements but AFAIK, we still don't know much about how a living entity works. So of course medicine is a lot of trial and error.

But to say in 2014 that we don't know how a capacitor works and how to engineering around any shortcomings is ludicrous.

 

RE: Apples and oranges, posted on January 30, 2015 at 12:50:31
morricab
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 "The medical industry still has vast unknowns." Not when it comes to designing and making drugs...it is all well know chemistry and physics. What we don't know about behavior in the body is quite analogous to what we don't know about how people respond to sound when listening to music. So, quite apples to apples...I am disappointed in you that you seem to have so badly not got the point...I assumed you were a pretty smart guy.

"So of course medicine is a lot of trial and error."
And you think making good sound is any less trial and error...LOL!! At this stage it is no better than medicine...worse in fact because at least we have clinical trials that show if it really works or not. Since audio won't kill anybody if its wrong then those controls don't exist in audio.

"But to say in 2014 that we don't know how a capacitor works and how to engineering around any shortcomings is ludicrous."

Clearly you have missed the point. I am not comparing understanding of medicine in a patient to a capacitor. I am comparing how drugs behave in a body to how music affects a person. We know a TON about how to make drugs and how to measure them...just like audio measurements. What we don't know is how they will behave in a body...just like we don't really know how measurements will affect the listener's perception.

I can't really make it any clearer than that...either you don't get it because your focus is so narrow or you are willfully misunderstanding the point.

 

RE: Have you heard any recordings that sound like the real thing?, posted on January 30, 2015 at 13:01:46
morricab
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 "I am simply making the point that when we listen to a CD, we are listening to a musical rendition that has come primarily through solid-state amplifiers. "

And I am simply saying it depends on the recording AND I am also saying that not all SS circuits are bad AND I am saying that most recordings suck or at least do not sound very realistic.

"If someone finds the vacuum-tube amplifier produces a more appealing sound, then the most economical and most plausible explanation for this is that this (N+1)'th stage in the process is *adding* a sound quality they like"

And I am telling you that the psychoacoustic data I have seen suggests that this is not the case.

"In other words, the fact that some people report that a vacuum-tube amplifier makes for a better sound, when playing CDs, strongly suggests that they like a specific colouration that the vacuum-tube amplifier adds to the audio signal."

You are ignoring the obvious alternative that SS amplifiers are adding additional colorations that people find less pleasant. ALL amplifiers add to the signal...whether and how its audible is the thing.

"It is also completely consistent with the hypothesis that the many solid-state stages on the route to the output of the CD player (modern technology, not early 1970s SS technology) are essentially reproducing "uncoloured" audio signals."

THis is only even partially true if you accept that most modern recordings are actually good...something I have already disputed. A good tube amps still lets you hear the flaws of the recording just fine...it simply doesn't exaggerate those flaws.

 

I think I get?, posted on January 30, 2015 at 13:10:38
gusser
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 You are saying that listening to music is an experience of mental stimulation and no two people will hear exactly the same things. Is that right? And of course someone may like the sound of a tube amp versus the SS amp.

And you have to admit there are mental biases involved.

But if we mask the test to where the bias is removed. If we test something that is immeasurable by ear as far as we know. Such as replacing copper wire with silver hookup wire. I think you are saying there could be someone that can actually hear that miniscule level difference.

I can't disprove that but it just seems implausible considering the numbers involved, which by the way are not in dispute.

If the test subject has any idea, even a hint in some cases which is which, the test is no good. And while I don't know much about psychology at all I have read the people unknowingly very often give away cues with their body language.

Hell, I wouldn't even discount some form of unconscious ESP that is telling the test subject which is which. But based on what I know about countless human hearing studies, no person should be able to resolve a difference between copper and silver hookup wire. The difference while present and even measurable is just to minute. But I could be wrong too.

 

RE: Have you heard any recordings that sound like the real thing?, posted on January 30, 2015 at 13:23:22
cpotl
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 "You are ignoring the obvious alternative that SS amplifiers are adding additional colorations that people find less pleasant. ALL amplifiers add to the signal...whether and how its audible is the thing."

But my point is that what comes out of the CD player has already been through so many stages of solid state amplification that merely adding one more SS stage (as an audio amplifier in the living room) would have a proportionately small effect; just an (N+1)-th stage after N previous stages of SS amplification, where N is large.

It is therefore much more plausible that if the vacuum tube amplifier in the living room is having a dramatic effect on the sound, then this is because of something it is adding, rather than that it is faithfully reproducing the results of the previous N stages of solid state amplification.

I really don't understand why the suggestion that a vacuum tube amplifier colours the sound in a characteristic way causes so much angst in some quarters. And if we consider a typical SET amplifier, for example, it has very easily measurable characteristics that could easily be responsible for colouring the sound, such as the typically large second-harmonic distortion.

In fact some proponents of SET amplifiers actively promote the second-harmonic distortion as the reason why the amplifiers have the characteristic sound they do. Is it just the use of the term "colouration of the sound" to describe it that is considered inappropriate?

"And I am telling you that the psychoacoustic data I have seen..."

I would be interested to see the data you are referring to. Can you give a citation to where I can find this? Thanks.

Chris

 

RE: Have you heard any recordings that sound like the real thing?, posted on January 30, 2015 at 14:12:14
Tre'
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 But aren't the largest distortions found in an output stage?

Yes, most recordings did go through many SS gain stages and caps, etc...but the last stage in the chain, the stage that allows the signal to drive a loud speaker, isn't that where most of the (total) distortion will be generated? (or maybe I should say where most of the total distortion is usually generated)

I'm just thinking out loud.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Have you heard any recordings that sound like the real thing?, posted on January 30, 2015 at 14:21:02
gusser
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 "But aren't the largest distortions found in an output stage?"

Basically yes. But many audio distribution line amplifiers can drive 30dbm into 100 ohms or less. They are actually small power amplifiers. And most OPAMPS are push pull in design as well.

But today most of the signal path past the initial mix console is digital. In fact most music post production is now file based on Pro Tools or the like. It's all shipped around facilities and beyond on standard IP networks. So it mostly only goes through a few A/D D/A conversions if even more then the initial digitizing.

Cpotl speaks more of the old analog days but his point is still right on.

 

RE: I don't get that., posted on January 30, 2015 at 17:17:02
op48no1
 A push-pull amp without feedback does not have inherently more distortion than a single-ended amplifier. In fact, it has much less.

A multi-stage amplifier needn't have excessively high levels of distortion. Really, you only need as many stages as required to get the desired gain. In this respect, push-pull amps are no different than single-ended amps.

The phase splitter is an added complication in a push-pull amp, but a good phase splitter need not add significant distortion.

-Henry

 

RE: Have you heard any recordings that sound like the real thing?, posted on January 31, 2015 at 05:22:29
Stephen R
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 I don't see any real problem with what any of you are saying in this branch of this thread.

Yup, the recording chain is a nightmare chain of events. It's amazing anything good comes out the other end. There are some recording chains that are less damaging than others but they all mangle or alter stuff in various ways.

And then you get the media to play with. There we have all kinds of preferences as to what we find "closest to the original" or maybe a medium that "sits well with our sensibilities".

And then after that, we have the big picture. The thing that really polarises everyone in this hobby. What speaker do we listen to this stuff on. That will determine what we drive it with. This is the bit where the greatest changes occur in sound and therefore taste.

And the flavour of "our stuff" is a constant. Every piece of media will sound different but the constant, the thing that allows us to tune the sound to what we like is largely the amp driving the speaker. And there, at that interface, for many, ir really does matter whether it's another +1 of SS distortion or whether it's another +1 of valve distortion.

I have a preference about which technology allows me to enjoy the music in my home more and technically, I can justify valve technology over SS technology if I want. It has technical characteristics, science if you will, that backs up what I hear.

cheers,

Stephen

 

RE: I don't get that., posted on January 31, 2015 at 14:26:24
morricab
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 "A push-pull amp without feedback does not have inherently more distortion than a single-ended amplifier. In fact, it has much less."

For a Class AB amp this is not true...for a Class A amp it could be true.

"A multi-stage amplifier needn't have excessively high levels of distortion. Really, you only need as many stages as required to get the desired gain. In this respect, push-pull amps are no different than single-ended amps.

The phase splitter is an added complication in a push-pull amp, but a good phase splitter need not add significant distortion."

You can make plenty of gain with a single stage...no need for multiple stages...unless you want to use a lot of feedback.

Phase splitters are notoriously difficult to make with low distortion.

 

RE: I don't get that., posted on January 31, 2015 at 16:15:44
op48no1
 Well, I don't want to get into a technical pissing contest, but there's nothing inherent about Class AB push-pull that makes it high-distortion. Granted, you tend to get higher-order kinks in the transfer function, but it's all a matter of choosing your operating point carefully. The distortion spectrum is very different with push-pull, and you may very well prefer the sound of single-ended (or push-pull Class A). But on an absolute magnitude scale, you need a hell of a lot of crossover distortion to make up for the reduction in even-order distortion that push-pull affords you. Somewhere in my files I have a couple of articles on this.

Whether or not you get enough gain from a single stage depends on the sensitivity of your output tubes and how much power you want to get out for a given input voltage. I like my amps to have 30dB of gain, which coincidentally corresponds to a voltage gain of 30. This is borderline attainable in a zero-feedback design, depending on what you're trying to achieve.

With respect to phase splitters, the current-sourced long-tail pair is pretty damned good. IIRC, Allen Wright had a zero-feedback 300B push-pull design with a cascade differential driver, and I assume it was very good. I've seen other push-pull zero-feedback amp designs as well.

I think the general consensus is that tube distortion is benign enough that you can pass a signal through several stages without issue. Most phono preamps are open-loop and run three stages, yet still sound good if designed properly.

Overall, I have to agree with the statement made here recently by someone else, that the biggest problem with negative feedback is instability. My experience with tube amps having modest amounts of feedback is that they sound like crap if they aren't stable, but absolutely amazing once the loop is stabilized properly.

I really don't see this "orthodoxy" thing. All tube amp designs are orthodox (or at least the ones that get talked about here). I don't have a personal beef with you so don't get me wrong. I just think, in a way, that feedback-bashing has kind of become the new hi-fi orthodoxy. Feedback is a tool, and one that most people really don't understand.

-Henry

 

RE: I don't get that., posted on February 1, 2015 at 11:50:41
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 I agree there is no reason to take a piss on the forum...I assure I am having a serious debate here because I while I am well aware of what different circuits do technically to a circuit I am also pretty convinced that most engineers don't really know what the sonic consequences are of a pursuit of technical perfection.

"But on an absolute magnitude scale, you need a hell of a lot of crossover distortion to make up for the reduction in even-order distortion that push-pull affords you. Somewhere in my files I have a couple of articles on this."

That is the crux of the problem...you don't need much crossover distortion to sound very objectionable...and it gets worse, relatively as the level goes down. The perception problem is strongly non-linear and it even seems that changing the distortion from monotonic to strongly odd order is also a perceptual no no. D.E.L Shorter proposed n(squared)/4 (where n is the harmonic order) as a weighting factor for the perceptual affect...later studies found that was not severe enough...read Cheever for a good overview on the history or the papers outlining the GedLee number by Earl Geddes.

"I like my amps to have 30dB of gain, which coincidentally corresponds to a voltage gain of 30. This is borderline attainable in a zero-feedback design, depending on what you're trying to achieve."

I find that most amps have too much gain...but feedback is not a good way to reduce it IMO.

"Allen Wright had a zero-feedback 300B push-pull design with a cascade differential driver, and I assume it was very good. I've seen other push-pull zero-feedback amp designs as well."

That amp was pretty speaker dependent. When the speaker was right though it was WHOA good.


"Overall, I have to agree with the statement made here recently by someone else, that the biggest problem with negative feedback is instability. My experience with tube amps having modest amounts of feedback is that they sound like crap if they aren't stable, but absolutely amazing once the loop is stabilized properly."

Well having had a couple of amps that had adjustable feedback I can say without a shadow of a doubt that they sounded better with the feedback switch to the minimum. Especially my VAC 30/30, which completely shrunk in sound even going from zero to the min feedback (2db I think)...going higher did even more damage to the sound. Now, maybe it was becoming unstable but there was no indication of this. I have yet to hear feedback make a real sound quality improvement.


"I really don't see this "orthodoxy" thing. All tube amp designs are orthodox (or at least the ones that get talked about here). I don't have a personal beef with you so don't get me wrong. I just think, in a way, that feedback-bashing has kind of become the new hi-fi orthodoxy. Feedback is a tool, and one that most people really don't understand."

It is not for me either. I do this in the purest scientific way...I first make observations...lots and lots of them...then start to ask "why do I prefer the sounds of these over these". Then start to read literature about what has been done to correlate sound quality and design...etc.

 

RE: I don't get that., posted on February 1, 2015 at 13:24:37
op48no1
 Thanks for the reply. I think we're on the same page here.

I have experienced expansion of the soundstage with decrease in feedback, but to me this was an artifact of added distortion, not an improvement due to reduced distortion. But, of course, this wasn't in an amp designed for low open-loop distortion in the first place.

To my ears, good solid-state amps are basically perfect (though it's hard to know for sure because there are so many unaccounted-for variables, and what is "perfect" sound anyway?). I hear differences between amps, and they are damned hard to explain with basic measurements. I believe the most complex and poorly-understood component in the chain is the listener. It doesn't follow at all that a "perfect" amplifier necessarily equates to "happiest listener."

I think from a system design perspective, the simplest approach is to build an amplifier that has the best possible measured performance, based on a suite of appropriate measurements; then go looking elsewhere to tailor the sound to your preferences. I think the "perfect" amplifier problem has been solved for all intents and purposes. It doesn't mean an "imperfect" amplifier won't sound better under some circumstances.

The audiophile belief that a good ear is in infallible measuring instrument strikes me as plain ass-backwards. It's a very complicated question.

Happily (for me), I've backed away from hard-core audiophile values after spending many frustrating years at it. Overall I'm happier now, but that's just my compromise, and I certainly respect people who want to keep drilling down in their quest for "The Absolute Sound..."

..As long as they don't tell me I'm a jerk for holding fast to certain beliefs about the physical nature of things that, so far, are working out very well for me in other areas of my life.

Regards,

Henry



 

RE: I don't get that., posted on February 1, 2015 at 15:45:32
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 "I have experienced expansion of the soundstage with decrease in feedback, but to me this was an artifact of added distortion, "

This is a pure (and incorrect) assumption on your part. In fact it has been noted that high order harmonics are associated with perceived loudness. What this means is that when these harmonics are present the sense of depth is reduced (as well as 3d imaging) because high frequencies, which are crucial to depth perception are exaggerated. This is well known from psychoacoustic studies.

"To my ears, good solid-state amps are basically perfect"

Not even remotely...read on for links discussing measurements and perception.

"I hear differences between amps, and they are damned hard to explain with basic measurements"

Exactly, which is in contradiction to your previous statement.

"It doesn't follow at all that a "perfect" amplifier necessarily equates to "happiest listener.""

Since all this stuff is only to make happy listeners I find this statement to be silly at best and truly missing the point at worst.

"I think from a system design perspective, the simplest approach is to build an amplifier that has the best possible measured performance, "

Simplest perhaps, the right way doubtful...at least with current tools at hand.

"based on a suite of appropriate measurements;"

It is not about appropriate measurements per se, it is using them along with psychoacoustic data and then CHANGING the design to get measurements that meet the right requirements. This is fundamentally different than designing as low as possible THD and IMD in the hopes that it sounds better...this has been the misguided way for the last 60 years. Read the links below where THD and IMD actually have weak NEGATIVE correlations with sound quality.

" I think the "perfect" amplifier problem has been solved for all intents and purposes"

Obviously this is your opinion and not at all anything like a consensus. It is clear from research that until a truly linear amplification device is invented then a perfect amplifier is far from available. These kinds of statements seriously make me doubt your understanding of just how complex the problem of perception and correlation to design truly is.

"The audiophile belief that a good ear is in infallible measuring instrument strikes me as plain ass-backwards. It's a very complicated question."

It is complicated that I will heartily agree. I don't think anyone is claiming an infallible ear but in the end, the messy and contradictory human is the final arbiter...not the scope. This means that there WILL be contradictions. The machine can only tell what is there but not its impact...I will say this over and over until it sinks in.

"As long as they don't tell me I'm a jerk for holding fast to certain beliefs about the physical nature of things that"

I don't think that but I think you will benefit from stepping out from your paradigm a bit and thinking about it more. Rather than saying "there is no way humans can hear that", instead approach it that they might be able to and if they can then there are serious implications with regard to different amplifier designs.

In the end, it is a hobby to enjoy music and I only take this seriously in as far as I like to know WHY things affect other things. I still sit down and enjoy music like most on this forum.


Now, here are some links...read them and tell me what you think.

http://gedlee.azurewebsites.net/Papers/THD_.pdf
http://gedlee.azurewebsites.net/Papers/Distortion_AES_I.pdf
http://gedlee.azurewebsites.net/Papers/Distortion_AES_II.pdf
http://www.dancheever.com/main/cheever_thesis_final.pdf


There is much more information out there (from Pass, Bernd Gottinger, Otala, Norman Crowhurst and others) but these summarize a lot of what is out there.

 

RE: I don't get that., posted on February 1, 2015 at 17:46:20
op48no1
 I think maybe you are taking this a bit more seriously than I am.

I kind of resent the fact that you seem to be calling me an idiot, but really, it's not that important to me. So if we have
to agree that I'm an idiot to avoid having a fight, I guess I'm cool with it.

I responded to your initial post just to comment on your claim that a multi-stage amplifier without feedback will have
very high distortion. I disagree with that. Everything after that seems to be sliding down the slippery slope into a
technical-argument-slash-male-chest-beating contest in which I am a only very reluctant participant.

The Geddes-Lee papers talk about metrics that better correlate between objective measures of distortion and listener
perceptions of distortion. This is good work. What I don't see in your citations is any data regarding the audibility of
distortions in state-of-the-art solid-state amplifiers. I agree that traditional THD and SMPTE IMD measurements are
pretty poor. Borbely talked about this in detail in his series of articles on a three-tone IMD analyzer published years
ago in "Audio Amateur." I personally believe that if you can engineer an amplifier that has vanishingly low static and
dynamic distortions, wide frequency response, low noise, low susceptibility to EMI, is stable, has a very low output
impedance, and flawless time-domain response, then you'd be very hard-pressed to find anything about it to fault,
listening-wise.

My anecdotal comments about what I've heard are scientifically meaningless and were not intended to be taken as
scientific generalizations of fact. I don't have the patience to go into all this in detail. If we were to get together to
put some of these ideas to a test, I think we're both smart enough that we would agree on the protocols and on the
resulting findings.

I'm particularly miffed that you dismiss my comment that a "perfect" amplifier may not the the one that makes listeners
the happiest. I suppose if you equate perfection and happiness then my statement is nonsensical. But I do believe
in the idea of euphonic distortions. Perception is complex enough, and the whole two-channel stereo concept is so
flawed anyway that it makes perfect sense to me that mathematically "perfect" amplification may not be preferable
to some listeners.

I'm surprised that you cite the Cheever paper. This is a master's thesis, not serious science. I've read it before and
I think it's embarrassing fluff. I always laugh at the very first statement: "Humans respond emotionally to complex
musical messages which contain no real survival value." He is so clearly talking out of his ass, this is so obviously
refutable, that it's hard to take anything seriously that follows in the paper. I would get into a more detailed critique
of the thesis, but to what end?

Finally, falling back again to subjective perception, when I try to listen seriously to a stereo system, I ask myself
whether or not the system gives me a seemingly transparent window on the music. I listen for grain or noise
"between" the notes. I listen for anything unpleasant or painful especially in the high frequencies. I try to assess
whether or not the experience is subjectively "involving." I can honestly say that good solid-state amps, including
the 100W MOSFET amp I built a few years ago using boards from a DiyAudio group buy, float my boat very nicely.
I hear what I want to hear, and I have nothing to complain about.

Anyway, I'd really like to get out of this argument. As I said, I have no real negative feelings toward you, even though
some of your comments have kind of struck me the wrong way. I'm disappointed that you have come away with a
negative impression of me, but as I said, I can live with it.

Go in peace.

-Henry





 

RE: I don't get that., posted on February 2, 2015 at 12:55:04
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 First, I don't think you are an idiot. Now that we have that out of the way I would like to address a few points...

It is clear that you are coming from an engineer's point of view regarding design, testing, specs etc. That's ok, but you have to think about something (something that I have to think about all the time in my line of work so maybe why I dwell on it with audio) are these specifications meaningfully describing how the product behaves for it's INTENDED purpose. If they are not for that purpose then at best they are defining some sort of minimum quality control on the basic function of a product but not how it actually performs.

"multi-stage amplifier without feedback will have very high distortion. I disagree with that. "

unless it is pure Class A it is mostly true. Take the feedback loop off any given amp with 0.001% or whatever distortion and see what you end up measuring...it might even be unstable, which is essentially 100% distortion.

"What I don't see in your citations is any data regarding the audibility of distortions in state-of-the-art solid-state amplifiers."

The types of distortions mentioned by Geddes mathematically are of the sort that will always be present to some degree in many push/pull feedback amps that are not pure Class A so specific examples are not really necessary. I can give you lots of links to measurements of what are considered SOTA solid state amps and the distortion patterns you will see are consistent with the mechanisms described by Geddes. There are many push/pull tube amps, running Class AB and with feedback that have the same issues even if it won't sound quite the same (Crowhurst writing in the 50s was talking about tube amps after all).

I find these two statements from you particularly contradictory:
"I agree that traditional THD and SMPTE IMD measurements are pretty poor."

"I personally believe that if you can engineer an amplifier that has vanishingly low static and
dynamic distortions, wide frequency response, low noise, low susceptibility to EMI, is stable, has a very low output impedance, and flawless time-domain response, then you'd be very hard-pressed to find anything about it to fault, listening-wise."

And yet that is exactly what Geddes found out...in fact there was a slightly NEGATIVE (but marginally insignificant...at least at 95% confidence) correlation! Now, how could this be that flawless measuring amps sound at best no better and at worst worse? Well, based on my studies it is the WAY they are "reducing" the distortion...it looks great with static tests but the reality is something different. Crowhurst basically showed that you are mostly just pushing the distortion around to different harmonics and making a multitude of distortion components such that it actually resembles a noise floor. Pass has shown that distortion "concentrates" into particular frequencies that can be many times higher than the static distortion levels (see his paper on the First Watt website). You can believe what you want but it doesn't seem to hold up to scrutiny.

"But I do believe in the idea of euphonic distortions. "

Keith Howard basically put this old chestnut to rest by adding distortion of particular patterns to a digital recording. He explored many variations and found the following: ALL degraded the sound as compared to the unadulterated track. So there was no addition that was "Euphonic" all distortion added was bad; however, he also found that the monotonic distortion pattern (even and odd in a exponential decay in level with increasing order) was the least damaging of those he tried. Since there is no such thing as a distortion free electronic device this is an important finding, IMO. I have downloaded his software (he made it freely available) and done this myself with a recording I found to be revealing and got about the same results as Keith.

So, I DO NOT believe in euphonic distortion as it has been suitably proven to me that all distortion is damaging and it is a question of which is worse and which is better and level is only a small part of that (as would be obvious from the Gedlee number, Cheever's analysis and/or Shorter's equations for weighting harmonics).


"This is a master's thesis, not serious science. "

WHAT!!?? How is a Master's thesis not serious science?? I have a Ph.D. in Analytical Chemistry so is my Ph.D. Thesis also not serious science?? It is in fact one of the definitions by which I get to call myself a doctor of Chemistry and a scientist. The only difference in a master's thesis and a Ph.D. thesis is the scope of the work...a master's thesis is based on a more narrowly focused line of research and may have more direct support from the supervisor. I would be really curious about how you arrive at such a preposterous claim.

"He is so clearly talking out of his ass, this is so obviously refutable, that it's hard to take anything seriously that follows in the paper. "

A guy makes one questionable comment and you dismiss the whole work...seems pretty harsh to me...a lot of great men would have been discredited by this reasoning. His review is quite good and his conclusions match well with Geddes and others.


"Finally, falling back again to subjective perception, when I try to listen seriously to a stereo system, I ask myself whether or not the system gives me a seemingly transparent window on the music. I listen for grain or noise "between" the notes. I listen for anything unpleasant or painful especially in the high frequencies. I try to assess whether or not the experience is subjectively "involving." I can honestly say that good solid-state amps, including the 100W MOSFET amp I built a few years ago using boards from a DiyAudio group buy, float my boat very nicely. I hear what I want to hear, and I have nothing to complain about."

All fine with me and if that is what you hear it is what you hear...I would probably find something to be dissatisfied with in the sound of those designs...I have heard too many that didn't really work to be confident in the outcome.

 

RE: I don't get that., posted on February 2, 2015 at 14:19:52
op48no1
 I would like to respond, and we could go on for a few days, I think. I have a bunch of what I believe to be compelling rebuttals to the points you have made. I also think you make some good points of your own and would like to acknowledge them.

Unfortunately, I am just having trouble working up the motivation for the discussion. I'm really sorry because you and I could evidently have a pretty substantial debate here, and that would be a rare thing on this forum.

It's really my fault, and I beg your indulgence, but all of a sudden I'm thinking of the hours, days, weeks, and months I used spend in this kind of activity. And I realize I'm happier when I just let it go.

Again, please accept my apologies. Hopefully someone else will come along and keep this discussion going. I would be interested to read the follow-ups.

-Henry

 

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