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My criteria for a POTENTIALLY good sounding amp

160.62.4.10
Posted on June 18, 2012 at 07:22:50
morricab
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 I have been thinking for a long time about what design/measurements that are readily available to use as selection criteria for an amplifier.

I have distilled the ideas down into these guidelines. However, the final judgement is always in the listening, I am afterall and empirical scientist and don't rely on what people "know" to be good sound. Keep in mind that I have reached these guidelines by an empirical approach. When I heard an amp that sounded REALLY good I went and found as much info on the design and/or measurements as possible. After doing this for a long time I now have the following rules of thumb:

1) The amp must be Class A or high bias AB (around 15-20 watts A)
2) The amp must have little to no negative feedback or at least no global feedback
3) The amp must have a large, low impedance power supply
4) If the amp is tube output it must have LARGE output transformers that do not easily saturate, or be an OTL without much negative feedback
5) It should be simple in design, having only 2 or 3 total stages from input to output

6) The distortion should increase linearly (or nearly so) with power (also indicates a low feedback design)

7) The distortion should remain constant as a function of frequency, i.e. no rise at high frequencies as is often seen in SS and some tube amps and no rise in bass frequencies as is often seen in tube amps. This distortion is often far worse, harmonically, than the 1Khz typical measurent.

8) The damping factor should remain constant as a function of frequency

9) The harmonic distortion spectrum (usually taken at 1Khz) should be monotonic with a significant drop in level with increasing order and harmonics higher than about 5th should be down in the noise floor of the FFT.

10) Power supply ripple should be minimized so that distortion products do not produce intermodulation distortion products with the power supply harmonics. This results in a "dirty" noise floor.

11) IMD products should be low order like the harmonic distortion products.

If an amp meets most or all of these criteria then it probably has a good chance of being an excellent sounding amplifier. If it fails most then it will likely be mediocre at best and often quite "hifi" sounding rather than musical.

Again, this is an empirical observation and is open to reinterpretation if an amplifier that fails most of these criteria actually sounds really good to me. I haven't found it so far...

 

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RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 09:44:50
Disbeliever
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 Have a listen to the new Quad QSP and avoid tubes.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 09:47:05
Disbeliever
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 Have a listen to the new Quad QSP and avoid tubes. Review on Positive feedback Online or for a lot of money try the Devialet Premier,best according to HFN & RR however I do not believe them.

 

why avoid tubes? In my opinion, - they are a requirement -t , posted on June 18, 2012 at 09:47:08
Sordidman
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 .

"Asylums with doors open wide,
Where people had paid to see inside,
For entertainment they watch his body twist
Behind his eyes he says, 'I still exist.'"

 

RE: why avoid tubes? In my opinion, - they are a requirement -t , posted on June 18, 2012 at 09:50:55
Disbeliever
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 Because if you want accuracy and to be able to drive any speaker properly avoid tubes.

 

accuracy? That's a moving target....., posted on June 18, 2012 at 10:07:02
Sordidman
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 Hybrid tube amps are just as "accurate."

But since there's not an universal definition, - it's left to individuals to decide for themselves..


"Asylums with doors open wide,
Where people had paid to see inside,
For entertainment they watch his body twist
Behind his eyes he says, 'I still exist.'"

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 10:17:04
morricab
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 Heard it on rebuilt Quad 63 and 57 and, as always with Quad amps, not impressed at all. Nice try, not!

Haven't heard the Devialet yet but based on the reviews and the subtle remarks regardin tone in them, I think I will come away as I do with all Class D and that is, thanks but no thanks. Everyone was touting the latest NuForce reference monos. I heard them with a very revealing pair of Piega speakers and the result was close to fingernails on the chalkboard. Rubbish.

 

RE: accuracy? That's a moving target....., posted on June 18, 2012 at 10:17:35
Disbeliever
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 More Euphonic than accurate, very old tech.

 

RE: accuracy? That's a moving target....., posted on June 18, 2012 at 10:22:55
morricab
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 I wouldn't slip too far down the subjectivist slope, Sordidman. There is something to compare against and that is the real live thing. My criteria are based on observations of gear that gave me more a sense of the live than others.

 

RE: accuracy? That's a moving target....., posted on June 18, 2012 at 10:31:57
Disbeliever
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 Let me know when you find a stereo amp worth listening to . Whilst I quite like the sound of the Quad QSP into transmission line speakers, I have rejected two of them due to their lack of a proper protection system. IAG agree there is a problem and they say they have a solution, I will believe it when I experience it. I gave up on the 63's long long ago they can not be used now to judge the sound of the latest amps.

 

You might as well bang your head against a brick wall..., posted on June 18, 2012 at 10:45:35
Ozzy
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 ....instead of wasting your time with this guy. The results will surely be the same.

Oz



Don't worry about avoiding temptation. As you grow older, it will avoid you.
- Winston Churchill

 

Which of those requirements would you attribute to the downfall (according to you) of Soulution amp?, posted on June 18, 2012 at 10:59:27
carcass93
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 It clearly meets some of your criteria, at least #1, #3 and #9.

 

Agreed! Either your head will end up sore on the inside OR the outside...N/T, posted on June 18, 2012 at 11:27:30
musetap
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 N/T
"Once this was all Black Plasma and Imagination"-Michael McClure



 

two different paradigms, posted on June 18, 2012 at 12:26:30
Ralph
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 It would be a mistake to assume that just because there are tubes, that it is thus euphonic. What if the tube design is fully differential? There will be no '2nd harmonic sound' that tubes are so 'famous' for.

Plus as you will see if you read the link below, that there are two different ways of driving loudspeakers; not all speakers are the same!

 

agreed on all counts! Thanks for putting this up., posted on June 18, 2012 at 12:46:24
Ralph
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 The idea is that the amp have linearity without the need for feedback.

The issue then becomes, how do you drive speakers that are clearly made for amps with a very low 'output impedance' (I use the quotes for a reason, which is that the term is not entirely factual)?

What I have found is that if the speaker has these requirements of the amp then it will never sound like real music on account of such amps in and of themselves can't sound like real music because of the limitations imposed by feedback and the like.

This then requires that the speaker is able to accommodate an amplifier with a higher output impedance. This requires different box design (if it is a box) and also different crossover design. With respect to the latter, if you use the wrong amps with the wrong speakers, the crossover might be a couple of octaves off! This is why some horns will 'honk' with some transistor amps. There is more at the link.

Essentially for the most part the industry has been headed down the wrong road for about the last 45 years. What I mean by this is that the human hearing rules are pretty much ignored in favor of specs on paper. The former is why some amps sound good with "poor specs", the latter is why some amps sell better, as the specs on paper can make a bad amp look good.

 

Sorry guys, - you are correct: too much shilling from him -t, posted on June 18, 2012 at 13:14:14
Sordidman
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 .

"Asylums with doors open wide,
Where people had paid to see inside,
For entertainment they watch his body twist
Behind his eyes he says, 'I still exist.'"

 

What "human hearing rules" are you referring to? nt , posted on June 18, 2012 at 14:01:05
Rick W
 nt

 

Well, that does depend on how close your recording is, posted on June 18, 2012 at 14:07:24
Sordidman
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 to the real live thing.....

Sadly, - almost all recordings, (in my experience), are not so close and do not correlate well to the real live thing. And every recording, (even a small chamber ensemble), makes a choice of recording equipment.

In your position, you can say, - "this recording, played back through this system, was pretty OK and close compared to what I heard."

I respect that, and having heard probably more than a few of the same components that you have, - I am reluctant to disagree. I would just say that you are largely right, and I think that people can get close to a decent definition of accuracy, and come to similar conclusions through experiences, and numerous comparisons.

The choices that the recording engineer makes though, do affect the final outcome.

careful....



"Asylums with doors open wide,
Where people had paid to see inside,
For entertainment they watch his body twist
Behind his eyes he says, 'I still exist.'"

 

It fails on at least three counts, posted on June 18, 2012 at 14:27:30
E-Stat
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 1. Current dumper runs class B
2. Power supply transformer for 140 watts/channel only 600 VA
3. Use of op amps involves lots of feedback

 

RE: agreed on all counts! Thanks for putting this up., posted on June 18, 2012 at 14:47:53
morricab
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 Well Ralph, I have heard some amps that can drive difficult speakers and still sound great. Some of those speakers even sound great (such as the Apogee Scintilla) when driven by a great amp that can handle them.

For example, I have some friends who are Apogee nuts (I also owned Apogee) and several of them have Scintillas. The hunt was on for a great sounding amp that could handle those bad boys. What we found was this:
Sphinx Project 16 sounds great with the Scintillas. It is a 100 watt Class A hybrid beast that has adjustable power supply depending on the load.
Lamm M1.1 also drives Scintillas well and sounds good in the process

VacuumState prototype (not sure if it went commercial before Allen died). Allen brought this over to my friends and we demoed it on the Scintilla. 150 watts into 1 ohm! A tube amp designed specifically for Scintillas and sounded great.

For somewhat less demanding speakers there are a number of good hybrid amps that don't use any or only a little negative feedback. The Einstein Light in the Dark is a good example and I think its even a circoltron design. The AcousticPlan Santor is another very good sounding hybrid and drove Apogee Divas beautifully. For a low budget there is even the excellent sounding Monarchy Audio SE250. And if you have a big budget then the KR Audio Kronzilla SX will give just about anything (yes even your amps Ralph) a run for their money.

 

RE: Which of those requirements would you attribute to the downfall (according to you) of Soulution amp?, posted on June 18, 2012 at 14:58:24
morricab
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 Umm actually they are the poster child for wrong measurements. Look here:
http://www.stereophile.com/content/soulution-710-power-amplifier-measurements

I will explain. 1) downward sloping distortion with increasing power = high negative feedback design. 2)Increasing distortion with increasing frequency. The best sounding amps have a flat distortion vs. frequency plot. 3) FFT spectrum of 1Khz shows significant distoriton products to at least the 9th harmonic with odd harmonics dominating, so it is not monotonic, i.e. decreasing sharply with increasing order.

So, it is violating most of my measurement "shoulds" but I guess it must have a big power supply but runs only a bit in Class A I suppose.

 

Read Ralph's linked paper for the details. (nt), posted on June 18, 2012 at 15:04:52
jbrrp1
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 .

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 18:52:24
RGA
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 Well done and not just because I agree.

I remember the first time I heard the Sugden A21a. This was before I ever heard a tube amplifier. It was immediately the best sounding thing in the shop but I purchased an Arcam because as a beginner I put faith in reviews over my ears. Mistake.

But then over the next several years I put some of these things together - the best amps were pure class A little to no feedback, single ended or at least class A with low feedback. As for some of the power demands it depends on the requirements of the speakers. And of course from your list you have to make certain accommodations with budget. Obviously you can't expect the same from a $2000 amp that you would expect of a $25,000 amp. But like with Sugden or many tube amps - you try to check as many off the list as you can.

 

A thought provoking post..., posted on June 18, 2012 at 19:15:21
rick_m
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 And them's the best sort! Thanks.

I'm trying to boil it down, so far I think it means that you can stand very little crossover distortion and need a lot of gain-bandwidth if you use feedback.

Regards, Rick

 

I would like to read comments from Charles Hansen and Victor Komenho on this post, posted on June 18, 2012 at 19:52:49
Mike K
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 While I certainly do not disagree with anything you write, I think it
would be constructive to hear from experienced designers. I mention
Charles and Victor only because they are heard from here on a semi-
regular basis.

Lack of skill dictates economy of style. - Joey Ramone

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 20:00:23
Lord Soth
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 Just get an SET tube amp and a pair of Klipsch Hi-efficiency speakers and be done with it! ;)

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 20:32:44
hahax@verizon.net
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 I once asked two very good designers what measurement correlated best to what they heard since it wasn't the classic things being measured. The reply was one, linearity. If an amp takes in say one volt and puts out 5 volts then 2 volts in should be 10 out. The aplifier that does that most closely sounded best to them.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 21:23:33
Wojciech
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 My criteria would be not to use speakers which require more than 20W and especially pannel speakers which are for alliens with their strange properties;) Morricab ,since you favor those strange, unnatural emiters your need for beefy transformers which have to loose something in the HF perfomance (there is no other way around) is totaly understandable ;)
Truth to be told I have no clue what my criteria would be.There is always an example which doesn't fit and plays better that the ones which fit perfectly. I listen to opera for a week than I go to a worst country club and ask my girl not to shower for three days... , how can I do with one amp ;?) b rgsd W

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 18, 2012 at 21:57:26
DrChaos
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Sure, that's the goal.

But the devil is how to measure deviations from linearity which is psychoacoustically important.

 

RE: It fails on at least three counts, posted on June 18, 2012 at 22:37:15
Disbeliever
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 QSP 600VA ? only 469VA according to IAG service but it still sounds very good, far better than any Class D amp. only problem is lack of proper relay protection now being sorted or so they say.

 

Linearity is so underated but is the most important spec off all , posted on June 19, 2012 at 04:47:14
3db
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 Great post!!! It cuts through most of the crap that has been posted here.

This spec is very easily measured with the most basic of equipement. It ain't rocket science. Linearity demonstrates that an amp will be able to amplify a signal without causing any anomalies in the frequency domain. Extremely important...more important than SNR IHO.


Linearity is also very important in speaker response too. A linear speaker will ALWAYS sound better than a non linear speaker.


 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 19, 2012 at 04:50:56
3db
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 Linearity is just a ratio..very easily measured.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 19, 2012 at 05:42:29
morricab
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 Well that may be true about the HF roll off, although my KR measures flat to 25Khz and the distortion at 20Hz at 10 watts is less than 1%. That is wide enough bandwidth and low enough distortion for me. The larger Kronzilla models (mine is a VA350i) do have a bit more rolloff in the highs (-2db or so at 20Khz) but mostly this is inaudible and is more than a fair tradeoff to have deep natural sounding bass and clear, uncolored mids.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 19, 2012 at 05:44:56
morricab
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 Good SETs meet most if not all of my criteria. Not so good ones do not. Most fail with the output tranformer quality and the bass distortion (i.e. distortion vs. frequency).

 

RE: A thought provoking post..., posted on June 19, 2012 at 05:46:38
morricab
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 I have only heard a handful of good sounding amplifiers with small amounts of feedback and none sounding good with a lot of feedback.

 

I found the transformer size, posted on June 19, 2012 at 06:09:58
E-Stat
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 on this website.

That is half the size of my thirty year old Threshold for 100 watts / channel. Click the radio button for the QSP.

only problem is lack of proper relay protection now being sorted or so they say.

Like the 405. Maybe one day, they'll build the output stage strong enough such that it won't need protection.

 

See: Halcro, by all measurements the perfect amplifier., posted on June 19, 2012 at 07:00:53
jihad
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 You want minimal crossover distortion in class B amps, class AB amps show worse crossover distortion which can be audible.

Sure higher bias sounds better, and you may not leave class A operation depeding on your listening habits, but.............

IME and IMO, there is no comparision between class A and class AB or B, Class A amps do sound superior.

You also want a high PSRR overall as well as for each individual stage. This can make or break an amp's performance often making power supply quality less of an issue.

You want good open loop performance, meaning gain and frequency response. Feedback should be used as/if/when needed and should not be shunned, IMO.

I would chose lateral mosfets as output devices. In my limited desgin/building expereience they do sound superior to BJTs, all things not being equal.
















Never attribute to malice that which can be adequately explained by stupidity.

 

RE: What "human hearing rules" are you referring to? nt , posted on June 19, 2012 at 07:58:27
Ralph
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 One of the most prominent is how the human ear detects the volume or sound pressure of a sound. It is done by processing the odd ordered harmonics of that sound. If you know the effects of loop negative feedback on an amplifier, then you also now know how this runs counter to how we hear!

 

RE: agreed on all counts! Thanks for putting this up., posted on June 19, 2012 at 08:15:32
Ralph
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 This may be going back a stretch but in one of the first reviews on any of our amplifiers the reviewer used a set of Apogee Full Ranges, which were also one ohm. We used a set of our Z-Music autoformers between the speaker and our (early) set of MA-1s and the result worked really well! IOW they were easy to drive other than their impedance.

However I should point something out. While an amplifier *may* be able to drive a difficult load, that is not the same as saying it is sounding its best when doing so- there is a reason why a difficult load is considered difficult- its harder for the amp to drive. While this logic is not rocket science by any means, it is a simple truth that lower impedances do not benefit high end audio reproduction at all, nor do difficult phase angles in the load.

With respect to impedance, its a simple fact that you will get more power, more bandwidth and lower distortion if a tube amp with an output transformer is driving a higher impedance (IOW it will sound better). What most people don't realize is that while they will not make more power, otherwise this is also true of any transistor amp. You can see it in their specs. Four ohms came in as a way to get amps to make more power since efficiency had taken a back seat to the cost of the driver itself. This is a historical situation; these days many audiophile accept four ohms and don't think much about it but there was a time when it was unusual and for good reason.

IOW four ohms has no benefit to reproduction if sound quality is your goal. If on the other hand sound pressure is your goal then there is a slight advantage if you have a transistor amp that can manage it. I've not gone into speaker cables but they are critical on four ohms where they are far less so on eight or sixteen.

These things that I have mentioned here are not only audible but also measurable. FWIW I don't agree that the Lamm you mentioned is serious competition although I am sure its a very competent amplifier. Someday maybe we should have shoot-out :)

 

Sometimes when you buy laboratory grade equipment..., posted on June 19, 2012 at 08:19:08
airtime
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 that is what you may end up with.

THe bottom line in audio is proper matching. And of course auditioning a piece. Numbers and designs are great. But the end all is "how does it sound?"

Listen first

charles

 

Why so restrictive?, posted on June 19, 2012 at 11:08:49
Jon L
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 Sure, if I were to commission some new custom amps, I would probably order up a set of requirements similar to your list. However, I have ENJOYED music on amplifiers that fail your list, and I still think the most important thing is for an audiophile to use his experience to match up the sympatico speakers to the amp on hand and create an ancillary environment conducive to enjoyable sound, all with the type of music one listens to.

 

RE: Why so restrictive?, posted on June 19, 2012 at 12:36:15
morricab
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 Because as far as I am concerned most amps suck, big time. Most don't remotely capture an accurate sonic portrayl.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 19, 2012 at 13:04:25
jimmycj
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 i hate class d with a passion

 

Pass labs..., posted on June 19, 2012 at 13:47:19
slapshot
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 I'm curious...how would Pass lab amps, say the x250.5 or the like, fare with your criteria?

 

Not very well, I predict , posted on June 19, 2012 at 13:52:49
Pinkus
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 This is not based on my knowledge of amp design, but my knowledge of morricab's posts :-)

 

RE: Why so restrictive?, posted on June 20, 2012 at 06:12:35
3db
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Sounds very subjective and unsubstantiated to everyone but your ears. I'm so relieved I don't live with your misery.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 20, 2012 at 07:01:07
Lord Soth
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 Ok. Then get an SET made by either Bottlehead or by Decware.

That coupled with Klipsch Hi Eff speakers should meet any audiophile's requirements.

 

RE: Why so restrictive?, posted on June 20, 2012 at 08:35:45
morricab
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 The funny thing is that you think because I am super selective that I must be miserable because I can't be happy with "any old amp". Well, nothing could be further from the truth. It has been a quite enjoyable quest and now that I have found several amps that do meet these criteria (in total or mostly) then I also have choices for good sound.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 20, 2012 at 08:36:26
morricab
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 Most of them are just plain horrible.

 

RE: Pass labs..., posted on June 20, 2012 at 09:07:29
morricab
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 Not sure about the newer X250.5 but here are the measurements from the X1000 monos.
http://www.stereophile.com/content/pass-labs-x1000-monoblock-power-amplifier-measurements

IMO, they fail in a few ways. 1) there is a large rise in distortion at higher frequencies. 2)Distortion vs. power first goes down with increasing power, which indicates a moderate amount of feedback. 3)The distortion measured at 50Hz still shows quite a few harmonic components (mostly odd harmonics) and that doesn't account for the HF distortion rise. 4)The IM distortion has quite a few harmonics but this might not matter much

The Pass Aleph 1.2 has a similar problem with distortion vs. frequency but I don't think the FFT in this one is fair becuase it was done at 201W and this is about clipping for this amp. I don't think TJN really knows what to measure to be honest.

http://www.stereophile.com/content/pass-aleph-12-monoblock-power-amplifier-measurements

Bizzarely, the XA30.5 has a very bad distortion vs. frequency plot.

http://www.stereophile.com/content/pass-labs-xa305-power-amplifier-measurements

I haven't heard this amp but I would bet that it has not the best sounding highs despite being class A.

The 1Khz FFT shows a number of peaks and a lot of power supply related IM products with the signal (all that fuzz in the "noise" floor). The poor IMD results are largely due to the distortion vs. frequency problem.

Now, I have heard the original X250 and thought that is was a quite good amp...for SS with some negative feedback and not class A but that it can be bettered by a number of other competitors. I remember a review in Bound for Sound where the X350, which sounded worse to me than the X250, was not so favorably compared to a pair of Monarchy Audio SE250 monos, which sound very good to me and fit most of my criteria.

So, in answer, I think the X250 is an ok amplifier but not really special and I see that its brothers (none of which i have been terribly impressed with) fail a few criteria but that doesn't necessarily mean a fail sonically. Just means its less likely to be stellar.

 

Please use your deductive skills to analyze the Ayre MX-Rs, posted on June 20, 2012 at 09:42:55
Pinkus
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 http://www.stereophile.com/content/ayre-mx-r-monoblock-power-amplifier-measurements

Seems to meet all your requirements ... with no tubes to boot.

 

Buyers didn't think so, posted on June 20, 2012 at 13:21:21
Des
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  Since: August 2, 2000
They went belly up

D

 

Care to identify?, posted on June 20, 2012 at 13:38:14
woober goober
Audiophile

Posts: 727
Location: Atlanta
Joined: November 6, 2009
 "... I have found several amps that do meet these criteria (in total or mostly) ..."

Please, and these are?

 

RE: Buyers didn't think so, posted on June 20, 2012 at 14:06:16
jihad
Audiophile

Posts: 2342
Location: chain o' lakes
Joined: February 20, 2003
 That was kinda my point.


Never attribute to malice that which can be adequately explained by stupidity.

 

RE: Please use your deductive skills to analyze the Ayre MX-Rs, posted on June 20, 2012 at 14:50:26
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
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 might even sound good... I liked the Theta Dreadnaught that was designed by Charles Hansen. Haven't heard these new ones from Ayre though.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 21, 2012 at 00:13:46
Bill the K
Audiophile

Posts: 8385
Joined: June 3, 2006
 Perhaps a good idea to have criteria for potentially good sounding speakers along with the amp.

Cheers
Bill

 

"sounds very good, far better than any Class D amp." , posted on June 21, 2012 at 01:34:58
Vic D
 As someone who has auditioned "any" and every class D amplifier. Could you give us your impression of the Mola-Mola compared to the Nuforce Reference 18 as well as the circumstances in which you were able to audition them?

http://www.mola-mola.nl/index.htm

 

RE: "sounds very good, far better than any Class D amp." , posted on June 21, 2012 at 01:59:57
Disbeliever
Audiophile

Posts: 1877
Joined: June 1, 2012
 I have not auditioned any & every Class D amplifier. However from what I have heard so far I would not waste my time in auditioning anymore Class D amps. I am very happy with Class AB thank you.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 21, 2012 at 04:13:33
morricab
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Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Ok, but I will have to work hard on this because it is harder to generalize as I have heard successful designs coming from radically different designs/technologies. I would have to have criteria for types of speakers I think.

 

Interesting, posted on June 21, 2012 at 05:27:10
Bill the K
Audiophile

Posts: 8385
Joined: June 3, 2006
 I am not sure since the desired end result, whatever mode of design is used for the speaker, is good sound or lets say the musicality. Like saying a very well designed class A amp is better than a very well designed Class AB amp, perhaps we can conclude that a well designed sealed speaker is better than a well designed ported design. Well, there is great scope for discussion on the Speaker forum if you post there.

Cheers
Bill

 

Given ant thought to auditioning the Sanders Magtech? nT, posted on June 21, 2012 at 09:59:38
Vic D
 .

 

RE: Please use your deductive skills to analyze the Ayre MX-Rs, posted on June 22, 2012 at 04:05:27
morricab
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Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Ok, I had a look at the Ayre and my initial impression is that while it does some things right it does others wrong and as a result will also be a bit of mixed bag sonically (note: I have not heard this amp from Ayre but I have heard others and while not bad, I would not own one).

1) The distortion vs. frequeny at 8 ohms shows a modest rise at high frqeuencies but is better into lower impedance but higher across the board, which may be masking the rise. At least it doesn't rise even more into 4 or 2 ohms.

2)They claim zero feedback but the distortion vs. power curve suggests that there is at least some global feedback because it is far too flat with power. A good example of a no feedback curve can be found here:
http://www.soundstagemagazine.com/measurements/monarchy_se160/

See Chart 2 and chart 3 and 5. This is how a no feedback amp measures, although I would like to see less power supply garbage in Chart 5 as it is making the baseline a bit "fuzzy".

Also, the Lamm ML 1.1:
http://www.soundstagemagazine.com/measurements/lamm_ml11/

See Charts 2, 3 and 5 again.

I can tell you from experience that both of these amps sound very good. The Monarchy is an amazing bargain, the Lamm is not a bargain but arguably worth the money.

3)Having some feedback has consequences then on the FFT distortion spectrum. Figure 8 of the stereophile review:

http://www.stereophile.com/content/ayre-mx-r-monoblock-power-amplifier-measurements

Does not show a monotonicity to the distortion spectrum with high order harmonics at about the same level as the 2nd and 3rd harmonic. This usually occurs when there is feedback and amps that do this often sound mediocre. You also see this in Figures 9 and 10.

Compare this with the Monarchy and Lamm curves (Chart 5)

4) The IMD is pretty good

I am sure the power supply is more than capable as well, However, there are some circuit design choices that I think led to better "objective" numbers but might lead to sonic compromise. I am surprised to see the distortion vs. power and FFT spectra looking more like a typical feedback ampifier given their claim of no feedback.

For my money I would still audition but likely choose something else.

 

RE: Interesting, posted on June 22, 2012 at 12:37:41
morricab
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Posts: 9181
Location: switzerland
Joined: April 1, 2005
 I will start then by saying that for ultimate transparency, truth in timbre and most accurate reproduction of the input waveform (within dynamic limits) you cannot beat a good electrostatic or planar magnetic speaker. What they lack; slam, headroom, sometimes bass etc. are things that are often not really material to great sound. For some full-range models there is no better coherence and faithfulness to the recording to be found in all the most important ways. The delineation of soundstages is equally impressive.

THat said, there are also extrememly good conventional and conventional speakers and hybrids.

The best all-around pure ESLs I have heard were from Infinity, Genesis and Wisdom Audio.

 

RE: Care to identify?, posted on June 22, 2012 at 12:52:26
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Anything from KR Audio
CAT JL-2
Lamm ML1.1, ML2.1, M1.1 and 1.2
Monarchy Audio SE160 and SE250
Jadis Defy 7 mkIII (don't know about the measurements but sounds good)
VAC PHI 70, 30/30, 70/70
Antique Sound Labs Hurricane DT and Cadenza DT
Einstein Light in the Dark, The Absolute Tune and Final Cut OTLs
Atmasphere OTLs
Joule Electra OTLs
Vaic 52B reference (later Ayon 52B reference)
New Audio Frontiers 845 monoblocks and Stereo 845
Wyetech labs 572 stereo amp
AcousticPlan Santor
Sphinx Project 16
Sphinx Project 14
Silvaweld OTL reference monoblocks
Audio Note UK, P4SE monos
Bat VK75 and VK200/500 (good but not great)
Edge NL Reference monos (best SS I have heard)
NAT SE1,SE2SE, Symbiosis hybrid
Blue Circle Audio BC2,BC2.1, BC2000, BC200 series

 

RE: Interesting, posted on June 22, 2012 at 20:26:10
Bill the K
Audiophile

Posts: 8385
Joined: June 3, 2006
 I am in total agreement to your conclusions.

Regards
Bill

 

How does the old saying go?, posted on June 22, 2012 at 21:24:31
Charles Hansen
Manufacturer

Posts: 6984
Joined: August 1, 2001
 "I know just enough to get into trouble."

Or something like that.

 

Glad to see you're finally using global feedback, Charles..., posted on June 22, 2012 at 21:50:33
andy_c
Audiophile

Posts: 1470
Joined: June 2, 2007
 It must be true, because I read it in The Audio Poseur!

:-)

Edit: Yes, I know you would never do that!

 

RE: Interesting, posted on June 22, 2012 at 23:32:05
Disbeliever
Audiophile

Posts: 1877
Joined: June 1, 2012
 I totally disagree, I have no interest whatsoever in tube amps , planar & stat speakers or subwoofers.

 

RE: How does the old saying go?, posted on June 23, 2012 at 01:12:23
givemevinyl
Audiophile

Posts: 192
Joined: January 5, 2009
 I believe it's, "A little knowledge can be dangerous." True, indeed.

 

Exactly., posted on June 23, 2012 at 04:51:22
Charles Hansen
Manufacturer

Posts: 6984
Joined: August 1, 2001
 After all, they wouldn't print it if it weren't true.

Heard you moved. Austin? Nice town.

 

You're saying we should look at SPECIFICATIONS ?!?, posted on June 23, 2012 at 07:54:38
Feanor
Audiophile

Posts: 9873
Location: London, Ontario
Joined: June 17, 2003
Contributor
  Since: March 12, 2004
 ... and test results at least as a starting point.

Your criteria will eliminate a lot of amps early in the process. I think I've heard a few good amps that would have gone unheard.


Dmitri Shostakovich

 

RE: You're saying we should look at SPECIFICATIONS ?!?, posted on June 23, 2012 at 11:05:04
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 No, I did not say look at specifications, measurements yes, specs no not really. Although if the spec for distortion is extremely low then I would say beware and the same if damping factor is given. Obviously, information about the design would help to judge (e.g. class A or not, negative feedback or not, power supply design etc.).

 

RE: Interesting, posted on June 23, 2012 at 11:06:12
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
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 maybe you should change your name from disbeliever to disinterested???

 

RE: Exactly., posted on June 23, 2012 at 11:21:34
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
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 So then, are you using local feedback around each stage or only around the input and driver and leaving the output out of the loop? You get in some ways similar measurements to darTZeel, who claims to use only local feedback loops, but they have higher distortion products and they also get a pretty flat distortion vs. power plot.

 

Ok but it's a fine line between specifications and design description -nt, posted on June 23, 2012 at 17:55:44
Feanor
Audiophile

Posts: 9873
Location: London, Ontario
Joined: June 17, 2003
Contributor
  Since: March 12, 2004
 nt


Dmitri Shostakovich

 

RE: Interesting, posted on June 23, 2012 at 22:43:59
Disbeliever
Audiophile

Posts: 1877
Joined: June 1, 2012
 I am very interested in musically accurate hi-rez multi-channel sound. Do not know of any recording studios who use antique tubes, planar or stat speakers for monitoring.

 

RE: Care to identify? Yet . . . , posted on June 24, 2012 at 08:32:23
Hi-Fi Nut


 
the list varies greatly, no? varies in topology, design, ss/tube/ etc. [forgetting money for the moment as that is not germane in your o.p.]

H.F.N.

 

RE: including the new integrated Audio Research? [no text], posted on June 24, 2012 at 08:35:44
Hi-Fi Nut


 
.

 

RE: "sounds very good, far better than any Class D amp." , posted on June 24, 2012 at 20:47:09
jimmycj
Audiophile

Posts: 1507
Joined: December 6, 2004
 Same here

 

RE: Ok but it's a fine line between specifications and design description -nt, posted on June 25, 2012 at 02:23:40
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Not really.

Specifications are numbers; frequency response range (+-), input sensitivity, output impedance, THD, IMD, power (RMS), power (peak) etc.

Design description is just that; transistor or tube (or both), Class A, AB etc., one stage, two, three or more, direct coupled etc. etc. etc.

 

RE: Interesting, posted on June 25, 2012 at 02:25:12
morricab
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Posts: 9181
Location: switzerland
Joined: April 1, 2005
 I know of some that use tubes for making the recordings at least. Don't know about the monitoring but I know that Phillips classics used to use Audiostatic electrostatic speakers for monitoring.

 

RE: Care to identify? Yet . . . , posted on June 25, 2012 at 02:26:31
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Yes it does but I never said that there was ONE right topology that delivers (potentially) great sound. However; all the ones that I have heard which sound great do many things more similar than different.

 

RE: including the new integrated Audio Research? [no text], posted on June 25, 2012 at 02:27:50
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Don't know, haven't seen any measurments or heard it.

 

RE: Interesting, posted on June 25, 2012 at 05:22:19
Disbeliever
Audiophile

Posts: 1877
Joined: June 1, 2012
 " used to" are the operative words, name one major label that still uses antique tubes.

 

Thanks for the extensive list!, posted on June 25, 2012 at 05:37:23
woober goober
Audiophile

Posts: 727
Location: Atlanta
Joined: November 6, 2009
 I have never heard any of these except for the Atmasphere OTLs (which I liked very well driving Classic Audio Loudspeakers), though have heard of nearly all of them. Nice that not all of them are too awfully expensive (for me). Thank you again.

 

You missed a few good criterion., posted on June 25, 2012 at 05:55:23
jihad
Audiophile

Posts: 2342
Location: chain o' lakes
Joined: February 20, 2003
 You want minimal crossover distortion in class B amps, class AB amps show worse crossover distortion which can be audible.

Sure higher bias sounds better, and you may not leave class A operation depeding on your listening habits, but.............

IME and IMO, there is no comparision between class A and class AB or B, Class A amps do sound superior.

You also want a high PSRR overall as well as for each individual stage. This can make or break an amp's performance often making power supply quality less of an issue.

You want good open loop performance, meaning gain and frequency response. Feedback should be used as/if/when needed and should not be shunned, IMO.

I would chose lateral mosfets as output devices. In my limited desgin/building expereience they do sound superior to BJTs, all things not being equal.


Never attribute to malice that which can be adequately explained by stupidity.

 

RE: You missed a few good criterion., posted on June 25, 2012 at 07:07:45
rick_m
Audiophile

Posts: 6230
Location: Oregon
Joined: August 11, 2005
 "You want good open loop performance, meaning gain and frequency response."

CONGRATULATIONS! ! !

You 'get it'. Few do...

Rick

 

RE: Interesting, posted on June 25, 2012 at 07:48:31
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Why would I care what "major" labels are doing? That would be like saying Bose makes the best speakers because they are a "major" label.

 

RE: You missed a few good criterion., posted on June 25, 2012 at 07:54:41
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 "You want minimal crossover distortion in class B amps, class AB amps show worse crossover distortion which can be audible."

This usually shows up in the FFT at 1Khz as high order products.

"IME and IMO, there is no comparision between class A and class AB or B, Class A amps do sound superior"

Generally, I agree but there are some important exceptions.

"You also want a high PSRR overall as well as for each individual stage"

This you can also see in an FFT as the power supply harmonics will show up there and it also let's you see if there is IM distortion products between the signal harmonics and the power supply harmonics. Amps with almost no power supply noise also have very clean FFT spectra(at least with regard to the IM distortion).

"You want good open loop performance, meaning gain and frequency response. Feedback should be used as/if/when needed and should not be shunned, IMO."

Some of the amps I have heard that sounded really good had SOME feedback but I don't know of one that I heard that I really likeed that had a lot.

"I would chose lateral mosfets as output devices. In my limited desgin/building expereience they do sound superior to BJTs, all things not being equal."

I have heard both sound good so but I would say that BJTs are the least linear amplifying devices. However, you need to run them both as much Class A as possible (tubes too for that matter).

 

RE: Interesting, posted on June 25, 2012 at 08:33:08
Disbeliever
Audiophile

Posts: 1877
Joined: June 1, 2012
 So you are not interested in Hi-res.mch SACD from all the major labels. which minor labels are still using antique tubes for recording ?

 

RE: Interesting, posted on June 26, 2012 at 05:35:37
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Tacet and Water Lilly (at least they were until recently).

 

RE: agreed on all counts! Thanks for putting this up., posted on June 26, 2012 at 05:37:54
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Would you consider Einstein as serious competition to your products Ralph? I would...also their much less expensive hybrids are right up there.

 

I see the distinction, but to get back to specifications ..., posted on June 26, 2012 at 06:04:09
Feanor
Audiophile

Posts: 9873
Location: London, Ontario
Joined: June 17, 2003
Contributor
  Since: March 12, 2004
 Given you extensive discussion of test results in this thread, what you're saying is that published specifications are simplistic, not the objective measurements are irrelevant.

I applaud your efforts to connect measurements with underlying design, e.g. with use of feedback. I'm not so sure I agree with your "all feedback" is bad philosophy. You know, of course, the some designers believe that global feedback is better than local, and that fairly large amount of feedback is better than a little. They point out that their approach results in lower distortion of all types, including high order.

You like a certain sound -- no arguing with preferences -- but that's subjective. You like Monarchy for affordable equipment. But I swapped by a pair of SM-70 Pro's for a Class D Audio SDS-258. The latter is a different sound to be sure -- and better to my ear. (More resolved, transparent, grain-free, and dynamic.)




Dmitri Shostakovich

 

Biased or prejudiced towards an amp according to topology or devices used. , posted on June 26, 2012 at 09:51:04
jihad
Audiophile

Posts: 2342
Location: chain o' lakes
Joined: February 20, 2003
 Not really a good idea, you might miss an outstanding performer.




Never attribute to malice that which can be adequately explained by stupidity.

 

yes and no., posted on June 26, 2012 at 10:16:26
Ralph
Manufacturer

Posts: 4778
Location: Minnesota
Joined: April 24, 2002
 They are using circuits that we pioneered- yes, they are competition but they've yet to break the price barrier. So we have amps for about 1/4 the cost of theirs that are more reliable and sound better.

Of course, they like to use negative feedback and don't use class A.

There is a sort of 'trap' with OTLs where the designer tries to make the amp do things that it really shouldn't be, in an effort to show off what the amp can do. If you just accept the fact that an OTL might have a higher 'output impedance' (I put the term in quotes as under the Voltage Paradigm, the term is misused) then the thing to do is to look at whether that is important and what are the consequences.

Using negative feedback makes the amplifier violate a fundamental rule of human hearing, IOW it exacerbates odd-ordered harmonic distortion. The violation is that the ear uses odd-orders to determine how loud a sound is, so such an amp will sound artificially louder and brighter than the actual music.

This means that any amplifier built in this way cannot sound like real music!

So if a speaker demands this of an amplifier it in turn cannot sound like real music either. Since the Einstein commits this sin, it will never sound right. That, other than the price, is the reason we beat them on a level playing field.

 

RE: Biased or prejudiced towards an amp according to topology or devices used. , posted on June 27, 2012 at 07:39:06
morricab
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Posts: 9181
Location: switzerland
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 These criteria are not biased towards a device or topology. However, certain topologies will never result in the desired measurements that I think usually result in at least good sound if not great sound.

 

RE: I see the distinction, but to get back to specifications ..., posted on June 27, 2012 at 07:58:32
morricab
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Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Well, I have never made any attempt to hide that these are criteria that I think are necessary to have a chance for really good sound. Again, I use it as a starting point for deciding to audition something or not and this comes from a lot of negative listening experiences for which I have then found measurements of the device in question. Since there is quite a bit of literature out there with measurements (thanks to Stereophile and Soundstage) and I have heard a lot of amps both really good and really bad I began to connect the dots to see where it led.

If the results had led me to a conclusion that the absolute level of distortion was important but harmonics not and that a rising distortion with frequency results in good sound and that a flat distortion with power increase is best then I would obviously posted different criteria. Alas, the devices that provided the best sound could be argued often to have the worst meausrements from an absolute distortion perspective. Why? I think it is because our hearing is not an oscilloscope or even FFT plot and that the way distortion is perceived is complex.

Nevertheless, it seems that if the distortion is predominantly low order and in a distinct decreasing pattern and that distortion is constant regardless of frequency then there is a good chance it will sound at least good. Once I decided this (and this was actually observed by the French reviewer Jean Hiraga 25 years ago or so) from looking at LOTS of curves of amps I knew pretty well, I think started to look at how they were designed.

Tube, transistor, Class A or AB, hybrid, no feedback, no global feedback, big power supplies etc. That is where my criteria and the kind of amp that makes them comes from. The Monarchy SM70 is unlikely to meet all of these criteria but the SE160 and SE250 appear to meet most of the criteria and sound darn good. The SM70 sounds, ok, especially for the price.

Regardless of what you say about how you like your class D I haven't found one yet that sounds to my liking and I have owned 3 different ones and listened to at least a dozen others. I find them to sound quite unnatural from the mids up and the measurements show that they have problems up there. If they sounded really good I think I would have to find out what made them sound that way but so far its consistent with my hearing and measurement observations. I don't expect them to sound good now when I look at a new ones measurements and see the same old same old from the numbers.

I recently heard the newest Nuforce reference monos on a pair of highly revealing Piega planar/hybrid speakers (2nd to top model) and using a top of the line Moon cd player and the top Pass preamp. The sound was terrible. Simply terrible. The amp made the speaker sound completely disintegrated between the planar and the bass drivers and the mid/highs were thin pinched and forward. No tone in the strings of violins and everything a bit steely. Not nice. The Piegas gave the amps nowhere to hide.

My friends also like Monarchy Audio products. Two of them now have the Monarchy Audio NM24 (I have the original M24) DAC with DIP. It has gone toe-to-toe with the Resolution Audio Cantata and done quite well and sounds substantially better to me than the DCS Elgar.

 

RE: yes and no., posted on June 27, 2012 at 08:07:36
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Ah but don't you use some feedback on your smaller amps, Ralph? Also, I have looked at the measurements from the Einstein "The Absolute Tune" on Soundstage.com and it looks like it has very good measurements from a potential sonic standpoint. They may use some feedback but not too much as the distortion still rises smoothly with power. The distortion with frequency if flat and the harmonic distortion looks very good and completely free from power supply artifacts. Not bad I would say.

I have heard their products at length and find them to be very good sounding (but pricey as you have noted). I have heard their all tube OTLs and found them also to be very good but I haven't seen any measurements of them so I can't comment on what is happening there.


I have heard some of your products and also found them to be very good sounding (and less pricey as noted). Which is better would require a proper shootout with compatible speakers of course.

 

RE: My criteria for a POTENTIALLY good sounding amp, posted on June 27, 2012 at 08:50:32
villastrangiato
 The hyper focus on negative feedback and "tube sound" is a total red herring. I was listening to Kenwood and Accuphase high speed amps way back in the day when Dr. Ottala's work was still the "holy grail" of audio. In the real world, amps that have a flat response out to 500 khz are useless. The claimed audible improvements, if they even exist, are slight. What is far more problematic is the instability and lack of output current capability that wide bandwidth designs create. Moving coil loudspeakers (the vast majority in existence) are low impedance current driven devices that are typically not compatible with tube voltage amplifiers that possess high output impedance. Wide variations in a speaker's load impedance will always produce audible anomalies in the net response of a high output impedance amp/loudspeaker combination. And no matter what tube fanatics say, that is not a good thing. Their suggestion that speakers which possess wide load fluctuations are not "properly designed" is ludicrous.

Moderate use of negative feedback in a good Class AB design has no audible signature. And because transistors typically have much higher gain bandwidth products than tubes, some feedback is necessary. Threads like this are full of uninformed blanket statements that have little or no real world value. If negative feedback induced "time smear" were such a catastrophic problem, Kenwood would still be making and selling a version of its L07MkII - an amp I once owned that experienced wide band melt down. While it was a clean, noise free amp - I could not tell an audible difference between it and the Class AB Threshold and Crown that ultimately replaced it.

 

RE: yes and no., posted on June 27, 2012 at 09:25:00
Ralph
Manufacturer

Posts: 4778
Location: Minnesota
Joined: April 24, 2002
 Compatible speakers is indeed the issue. Since we have stayed away from any large amounts of feedback (only found in 1 or 2 db amounts in the M-60 and S-30) the amplifiers don't have a voltage response compatible with some speakers built using the Voltage Paradigm for reasons I stated earlier.

But that does not mean there is a shortage of speakers they can drive.

BTW, loop feedback is not responsible for the type of distortion response where you see a dip at low power and a rise in distortion as output power continues to decrease. That has more to do with how the 'phase splitting' is done.

I don't doubt that the Einstein is a good sounding amp. It had better be for the price and power! and the fact that its an OTL :)

Years ago we were faced with the issue of feedback and I found that whether or not it was beneficial had a lot to do with the speaker. We built a variety of amps that had switchable or variable feedback and it was through that experimentation that we heard how it could foreshorten the sound stage, mess with dynamics and create artificial brightness. I would love to use it (for that matter I would love to use transistors...) but getting the equipment to sound like real music is the goal.

 

RE: yes and no., posted on June 28, 2012 at 08:13:24
villastrangiato
 Ralph said:

"...getting the equipment to sound like real music is the goal."


That is your goal. The goal of others (myself included) is:


" to build systems that add or subtract nothing from the sound that is fed into them - in essence unadulterated reproduction of the original recorded signal."


To me, that means driving BOTH odd and even ordered harmonics into the range of inaudibility. For most "normal" people, with respect to amplifiers, that has already been accomplished using solid state equipment, tube equipment, and hybrid equipment. There will always be people who argue whether or not a sonic artifact that's 40 db down in volume from the fundamental is audible. For those folks, reason and rational discourse will always be a struggle. For the rest of us, the contribution of audible even harmonics or a rising top end due to increased impedance is never a "good thing" and is not what we consider to be in the category of equipment "sounding real". Whether or not real musical instruments produce even ordered harmonics is irrelevant. A tube amp that adds more of these harmonics is no better than a solid state amp that adds more odd ordered harmonics. Both need to stay below the threshold of audibility for a system to sound "real".

 

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