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What does DHT PP do differently/better then DHT SET?

62.44.134.16
Posted on August 3, 2014 at 07:36:36
Frihed89
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 It gives you more power, for sure. Lower distortion (a lot)? Greater bandwidth? Better dynamics? Let's assume you already have speakers that match well with a DHT SET.

 

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Can sound cleaner but loses the magic midrange. , posted on August 3, 2014 at 08:30:14
andy evans
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 PP in a DHT amp - and I've built a few - can sound a bit cleaner overall. My preference would be SE input stages and an interstage splitter - good one. You can lose the cathode bypass caps by using tubes in the tail or ss devices for constant current sinks. I loathe cathode bypass caps.

But I only get that magic in the midrange, and especially vocals, with SE. Or in my case PSE 4P1Ls.

Can't live without that magic. Must have it.

 

RE: Can sound cleaner but loses the magic midrange. , posted on August 3, 2014 at 10:18:36
Skip Pack
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 Here's a question that elaborates on OP's question. You can achieve push-pull operation by driving the output stage by the usual means but putting a normal SE (air-gapped) transformer on each output tube, connecting speakers hot-to-hot (essentially bridged). This avoids having the cores of the opts switch polarities. Could this capture the strengths of SE and conventional PP operation?

Thanks,

Skip

 

Class A, posted on August 3, 2014 at 11:24:34
Triode_Kingdom
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 It's possible that a PP amp operating in Class A might offer some benefit. In this topology, if the output tubes are well-matched, the instantaneous current draw from the amplifier's power supply essentially never varies. Filter caps are used primarily for filtering, and the need for the supply to provide a low Z path to ground over the audible frequency range is greatly diminished. Under these conditions, the power supply caps should in theory contribute much less of their own sound to the amplifier.

 

RE: Can sound cleaner but loses the magic midrange. , posted on August 3, 2014 at 15:18:54
Paul Joppa
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 Only one way to tell - experiment!

My theory is that the missing even-order harmonics (which you would get with either implementation of push-pull) are the cause of the more hollow sound of P-P even with no feedback. So I would not ecpect this to do what you hope it will.

The theory of reversing magnetics to which you refer does not match with what is actually known about core materials, so I don't believe that theory.

However, even if I am right on both theories, that does not by itself prove that it's not in the transformer - one must remember that theories are just theories, and data is still data - so much of what we hear is unsupported by any plausible theory at this point!

 

RE: Class A, posted on August 3, 2014 at 15:21:43
Paul Joppa
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 To follow up on that, one could make an amp with current-source cathode loads on both output and driver stages, forcing a truly constant current. It would be an educational experiment for sure!

 

RE: Class A (???), posted on August 3, 2014 at 17:14:13
Triode_Kingdom
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 "...current-source cathode loads on both output and driver stages, forcing a truly constant current."

Can you explain that for me? Shouldn't the cathodes of the output stages be held at as nearly constant a voltage as possible (as though a voltage source were attached)? Guess I don't understand your meaning...

 

RE: Class A (???), posted on August 3, 2014 at 20:17:01
Tre'
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Or this.

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

 

RE: Class A (???), posted on August 3, 2014 at 20:38:04
Paul Joppa
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 I was thinking of cascaded "long-tail pair" differential amp stages. With a current source the "tail" does not need to be so long and inefficient.

The LTP is sometimes used as a phase splitter. Sometimes the common (shared) cathode resistor in a P-P output stage is left unbypassed; you might call that a short-tail pair diff amp. :^)

 

RE: Class A (???), posted on August 4, 2014 at 07:14:27
Triode_Kingdom
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 I seem to remember proposing the same concept some years ago on this forum. The only difference was that I used chokes as CCSs. Guess I wasn't the first to think of it. :)

 

RE: Can sound cleaner but loses the magic midrange. , posted on August 4, 2014 at 07:35:08
bwaslo
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 On the gapped-core thing in SE output transformers: this is done to avoid magnetic saturation of the core, right? What if the gap were filled by a permanent magnet opposing the magnetic flux caused by the SE tube's DC current?

Then the core wouldn't be gapped anymore (so it might be able to be made smaller?) but the core would be kept out of saturation by 'biasing' it with the magnet. Has this been tried (or is it just a stupid idea?).
_

Make easy high performance diffusors:-->http://www.libinst.com/diffusers/Depot_Diffuser.html

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RE: Class A (???), posted on August 4, 2014 at 08:20:05
nullspace
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 I've built an amp with that type output stage, using 2A3 and chokes in place of the CCSs.

I like it a lot. Rest of the amp is 1/2 of a 6n6p direct-coupled to a triode-connected 6w6gt driving a center-tapped autoformer phase splitter.

Regards,
John

 

Decware did something like this in one of their amps., posted on August 4, 2014 at 10:58:57
JJ Triode
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 I think it was the first-generation Torii PP, with triode-connected EL34 outputs, on an early version of the chassis they now use for their SE34i. They just used pairs of their existing SE OPTs back-to-back. I don't think they do this anymore, i.e. their present PP amps use conventional OPTs with center-tapped primaries.

 

RE: Class A (???), posted on August 4, 2014 at 12:00:46
Tre'
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I like this one even better and have a pair of OPT's that would allow for this type hook up.

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

 

RE: Class A (???), posted on August 4, 2014 at 12:17:10
nullspace
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 I tried it both ways. In my case, it both measured and sounded better the other way -- this way had increased 3h versus the other way.

Regards,
John

 

RE: Class A (???), posted on August 4, 2014 at 13:01:01
Tre'
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 Interesting.

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

 

RE: Can sound cleaner but loses the magic midrange. , posted on August 4, 2014 at 15:10:04
Paul Joppa
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 I had forgotten until now but this was proposed by Bascom King (Senior Editor of Audio magazine at the time) in VALVE v5n2 (1998). As he pointed out, this is called "bridged" when used with (P-P) solid state amps.

 

RE: Class A, posted on August 4, 2014 at 16:13:33
SteveBrown
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 Isn't this essentially what Allen Wright did in his fully differential PP amps (CCS on output and input/phase splitter)? Not the PP1 that's on the website, but the latter version (pp1-a, IIRC?).

 

RE: What does DHT PP do differently/better then DHT SET?, posted on August 4, 2014 at 16:29:43
hvbias
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 There was a thread over on DIYAudio somewhat recently on P-P vs SE. Once you get past the mudslinging someone posted measurements of their Karna inspired amp (IIRC using 46 as the 300B driver) and a 300B SET and at low levels the distortion spectra between the two were much more similar than different.

 

push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 4, 2014 at 19:52:53
Cleantimestream
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 sounds VERY clean with deep bass and absolutely no overhang.


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

 

RE: Can sound cleaner but loses the magic midrange. , posted on August 4, 2014 at 20:27:35
Skip Pack
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 Thanks Paul,

>Only one way to tell - experiment!

I'm not sure I'm up to buying six matched quality tranformers, but it would be fun!


>The theory of reversing magnetics to which you refer does not match with >what is actually known about core materials, so I don't believe that >theory.

This is certainly evidenced by your design preference for parafeed SE. My occasionally trustworthy ears place parafeed SE between series SE and PP class A. I don't trust my conclusions without at least a few months exposure in my own system, and your S.E.X. 2.0 is the only one in this comparison that I've heard for that period of time. I use and enjoy it to this day.

Skip



 

My experience, posted on August 5, 2014 at 03:43:57
morricab
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 I had the very nice VAC Renaissance 30/30, which is Class A 300B push/pull amplifier of overall very good design. I also have the JJ 322, which is a 300B parallel SET of also good design. The VAC has adjustable feedback (I left it on zero) and the JJ is zero feedback.

The VAC was very transparent with good tone and bass. However, it did not have that overall sense of coherence I get from my SET amps. The sound doesn't "breathe" in the same way as it does with the JJ or my NAT. In the end I preferred my SETs and sold the VAC. To be fair to the VAC, it is a truly great sounding amp and deserving of it's reputation. I would say it was more transparent sounding than my JJ (the NAT is just as good as the VAC in this regard) and had more powerful bass but the JJ gets that "performers in the room" thing much better while the VAC sounded a bit small sometimes.

I think Paul is probably right about the fundamental difference in harmonic distortion content between SET and PP that has nothing to do with feedback (which only makes the issues worse, IMO). This probably has an effect on the overall tonal balance as well as soundstage and image percepttion.

I would possibly try another triode PP amp just to see if it is inherent in the design or if it was just the VAC but I can't think of too many PP triode amps that best the VAC (Canary maybe??)? I would like to give the Antique Sound Labs Cadenza a try (push pull 845 in Class A could be interesting).

That said, I find good SET amps to be a more complete and wholly together sound than PP amps. Interestingly, my NAT is a hybrid SET with transistor output. It breathes nicely and has great tone and transparency but it doesn't have that tube "magic" in the midrange to the same degree as a great tube amp. Funny enough my previous amp, the KR Audio VA350i did have it even though the input and driver stages were transistor (so the exact reverse of the NAT)! Other than that observation, the NAT and the KR sound VERY simliar...which is to say fantastic. The JJ has another more wholly tube sound. It is not overly warm and fuzzy (it has really good output trannies that take care of that) but it is more rounded and projecting the midrange.

 

I believe you are right - thanks! (nt), posted on August 5, 2014 at 09:16:06
Paul Joppa
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 nt

 

RE: Can sound cleaner but loses the magic midrange. , posted on August 5, 2014 at 10:37:09
drlowmu
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 Andy,

Basically agree with you. As soon as you try to take the audio content, all of the music, and divide it into 180 degree counterparts, you are "messing with the siganl" TOO MUCH, and so, something always gets lost in the phase inversion.

This is where P-P goes awry, and it has little to nothing do with output transformer operation and design.

The trick is not to go P-P for a low powered amp...just make the SE amp BETTER in its design, layout, and topology.

KISS rules, always has, less is more IME !! So Andy, how can you get rid of the interstage in your favorite amp design, and use a Direct Couple, simple piece of Siltec wire to couple ???

Jeff Medwin

 

I don't direct couple because I use filament bias. , posted on August 5, 2014 at 14:43:12
andy evans
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 I don't direct couple because I use filament bias in all stages. I simply won't use cathode bypass caps.

Different way of doing it.

 

RE: Can sound cleaner but loses the magic midrange. , posted on August 6, 2014 at 00:57:35
grindstone
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 Just a sort of "hoot-out" for the board sponsors, really. Maybe a special shout to loonies like PJ who gutted-out the whole Thang (heya Dan).

Good thread, the sorts of which "here we used to be Lousy-with" (matey!?!??).

Thanks for keeping a channel open. Calendar informs me that it's 2014--lotta-folk have Quite Some lashups in the rearview since the Latest Renaissance :) Probably lots of us also would welcome an update from a lot of (long-silent but hopefully still-lurking) voices...

Please continue :)

 

RE: I don't direct couple because I use filament bias. , posted on August 6, 2014 at 01:02:18
shane.
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I direct couple and use filament bias.. without any cathode bypass caps too

Its a different way of thinking that allows this different way of doing it. :-)

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 6, 2014 at 11:18:19
Triode_Kingdom
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 This is very much a matter of overall design, not just topology. My 211 A2 SET monos are very tight and clean. I use about 6dB NFB to improve damping, and distortion measurements have confirmed what I hear. I don't put up with tube amps that can't perform. :)

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 6, 2014 at 15:09:49
Cleantimestream
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 Understood, the person asked what differences {or improvements} there were.

It is incontrovertible that 2nd order distortion is canceled with push/pull design.

I build amplifiers for fun and to create certain 'flavors' {for want of a better word] there is NO best in my world. I like the push/pull 45 for full tilt big band or symphony... not for Art Tatum or Charlie Parker on the bandstand.

Norman Crowhurst in the 50's validated through his groundbreaking research that several instruments derive their distinctive beautiful sound WITH and THROUGH 2nd order distortion... in other words... second order distortion in the right amounts, in the right order, is VITAL; if one likes certain {horns mainly} instruments.




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

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 6, 2014 at 19:06:13
Triode_Kingdom
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 "It is incontrovertible that 2nd order distortion is canceled with push/pull design."

Right, but my point was all SETs don't create the warm, full, bloomy synthesis you're referring to. Some, like mine, are dynamic and transparent, with all the harmonics very well controlled. Such amps reproduce music as accurately (some would say "more accurately") than any other topology. I for one enjoy both approaches - SET and PP - when done right. :)

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 06:31:47
Cleantimestream
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 are dynamic and transparent, with all the harmonics very well controlled"

While I would ascribe that to a power supply having Thorsten protocol of below 70 ohms for the entire circuit {12 henry choke with a dcr of 40 in my case} coupled with a superb driver stage, you DID state you use feedback {nested loop I hope} the only drawback I find with feedback is whenever used, I lose recording venue information {ambiance}.




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

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 08:21:07
Tre'
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 "Norman Crowhurst in the 50's validated through his groundbreaking research that several instruments derive their distinctive beautiful sound WITH and THROUGH 2nd order distortion...."

Instruments?

Second harmonic produced by the instruments will be part of the input signal and will not be cancelled by a push pull circuit.

Push pull circuits cancel 2nd ordered distortion produced by the circuit, not 2nd ordered harmonics that are part of the input signal.

Maybe I misunderstood your point.

BTW Overtones (harmonics) produced by an instrument are not referred to as "distortion".

When those overtones are RE-produced by an amplifier, they are not called distortion.

Overtones that are created by an amplifier circuit are called distortion.

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

 

RE: I don't direct couple because I use filament bias. , posted on August 7, 2014 at 12:10:40
drlowmu
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 Shane,

Next, eliminate the paralleled 2A3s and the 1 to 1 interstage, and you "got it ", on ALTEC, JBL, Klipsch, efficient speakers. Less is more.

Jeff Medwin

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 12:41:28
Cleantimestream
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 Instruments? Give this some thought and you will be able to extrapolate an answer, start with the King of instruments {a no-brainer, the organ}, the piano, any horn instrument and to a much lesser extent; all others.


Second harmonic produced by the instruments will be part of the input signal and will not be cancelled by a push pull circuit" This is obvious and no comment is necessary.

'Overtones (harmonics) produced by an instrument are not referred to as "distortion".' Correct, they are harmonics of the fundamentals and belong and are pleasing to the ear, I will now add, that DELIBERATE distortion added by an electrical guitar through an amplifier overdriven IS distortion AND is pleasing to the ear.

"Overtones that are created by an amplifier circuit are called distortion" No Sir. See my previous statement.

A set amp with varying amounts of 2nd order distortion IS pleasing to the ear. Years ago, a close friend and I were experimenting with a direct-coupled cathode follower SET design, we built one with a 2.5 K primary and a 5K primary ... otherwise identical. The 5K did indeed have lower distortion easily discerned via distortion analyzer and scope... made no difference, I preferred the 2.5K primary one {and so did he}... the finals tube in question was a triode wired 6V6.

Tis a bad day if I don't learn something.

What I WANT is the sound of a plasma tweeter, the midrange of my Quads and the bass of my Khorns.


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

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 14:24:32
Tre'
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 That's all fine but a guitar amplifier is part of the creative process, part of the input signal to the playback amplifier.

Anything that the playback amplifier outputs that is not part of the input signal is distortion.

Now to the rest of it.

"Norman Crowhurst in the 50's validated through his groundbreaking research that several instruments derive their distinctive beautiful sound WITH and THROUGH 2nd order distortion" (can you show me what he said that? I'm not going to search the whole text.)

NO! Several [acoustic] instruments derive their distinctive beautiful sound with and through overtones produced by the instruments themselves NOT with and through 2nd ordered distortion produced by an amplifier.

In playback the sound of these instruments may be enhanced, in your opinion, by added harmonic distortion created by the playback amplifier but that's a whole different thing than saying that the instrument itself creates distortion.

BTW I would have pick the 5k OPT with it's lower distortion because I want to hear the instruments and their *distinctive beautiful sound of the overtones produced by the instruments themselves*. No additives need apply.

But that's just my opinion. I don't have a problem with opinions but they should be kept separate from facts. It just seemed to me you were mixing the two.

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

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 15:41:15
Cleantimestream
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 Several [acoustic] instruments derive their distinctive beautiful sound with and through overtones produced by the instruments themselves NOT with and through 2nd ordered distortion produced by an amplifier"

Am not saying that. The inherent even order distortion found in musical instruments does indeed contribute to their beauty... as Norman Crowhurst states.

"In playback the sound of these instruments may be enhanced, in your opinion, by added harmonic distortion created by the playback amplifier but that's a whole different thing than saying that the instrument itself creates distortion." The instruments themselves DO create distortion, and pleasing @ that, rather upsetting... isn't it? Was for me.

BTW I would have pick the 5k OPT with it's lower distortion because I want to hear the instruments and their *distinctive beautiful sound of the overtones produced by the instruments themselves*. No additives need apply" Heh, heh. There in lies the rub. My intellect, my rationale, my tape measure said the same bloody thing. Charlie Parker playing Now's the time said the exact opposite... every time.

My advice. Advice? I highly recommend you read Crowhurst before you discuss any further with me. He is far more articulate than I despite saying the same thing as I have put forth to you above. Paradigm shifts are rare. You have been served.





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

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 16:16:01
Tre'
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 "The inherent even order distortion found in musical instruments does indeed contribute to their beauty"

I do understand what you are saying but I object to your use of the term "inherent even ordered distortion".

Acoustic instruments do not create distortion, they have overtones.

"Inherent even order overtones" would be the proper term.

Their sound is their sound, it is made up of fundamentals and overtones all produced by the instrument itself.

The difference between the sound of a violin and a viola playing the same A440 is the way the overtones are splayed out.

If you add something to that sound (through the creation of 2nd ordered harmonic distortion of the playback amplifier) then you have distortion (or, to say it a different way, you have distorted (changed) the natural sound of the instrument).

Can you please direct me to the part where Norman says acoustic instrument have distortion?

This is a slight distinction that makes a big difference in understanding.

When you play a A440 on the piano you will get 440, 880, 1320, 1760, etc..

The 880 that the piano is creating is not distortion, it's a natural overtone of the piano.

If you introduce 880 by means of the 2dn ordered distortion of the playback amplifier, even though it's the same note, it's distortion, not an overtone produced by the instrument.

I don't think my point is hard to understand.

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

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 17:41:07
Cleantimestream
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 This is a slight distinction that makes a big difference in understanding"

If you had the desire and perseverance for reading that important book, we would not be having this misunderstanding as you would understand the salient idea. The link will take you to someone whom has undoubtedly read Norman Crowhurst {One would have to read the whole book to understand} and he spells it out... indeed, the heading sums up what you want to dispute.

Their sound is their sound, it is made up of fundamentals and overtones all produced by the instrument itself" Yes Sir. Within that sound is distortion, sigh, not a perfect world. The human voice is an instrument... any argument there? Tom Waits voice distorts, so does Kate Bush... the spectra and magnitude differs. Never mind Charlie Parker always needing a new reed.


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

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 7, 2014 at 18:27:00
Tre'
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 You are using the term "distortions" differently than most.

See page 39.

This discussion has digressed into one of semantics and without clarifying will lead to misunderstanding in the broader sense.

No matter how "distorted" the input signal, changing it, in any way, results in what is normally called distortion.

Some of those distortions are very audibly objectionable and some are not.

If the playback could be made to be the same as the original then there would be no distortion in the playback and you will hear the "distortions" that were contained in the input signal.

Or you could add your favorite type of distortion to all input signals and live happily ever after.

Whatever.


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

 

RE: I don't direct couple because I use filament bias. , posted on August 7, 2014 at 19:08:51
shane.
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 Hi Jeff,

I'd like to.. I had it running with the 2A3 supply stacked on the input/driver B supply without the IT, it made me nervous enough with the OPT not being sufficiently rated for the voltage WRT 0V (UBT-1), had the core floating at 255V to make it sort of acceptable. I had TS jack for measuring driver filament voltage and it shorted, output stage ran away.. I don't know how it didnt melt down the OPT but I'm just not needing that sort of stress. It sounds good enough, perhaps not as good, but eh, you know.

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 8, 2014 at 08:25:10
Cleantimestream
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 I am using distortions differently than most ?

Myself, Floyd Toole {many others} and Fast Fourier Analysis are viewing distortion differently... just not in such a negative light.

I read well beyond 38, you will find page 45 enlightening.
The Mind has No Firewall~ U.S. Army War College.

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 8, 2014 at 18:29:20
Triode_Kingdom
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 Yes, you are using the term differently. The discussion was about distortion created in the amplifier, not about the overtones contained in the program material. If you wish to call the overtones inherent to the source "distortion," that's fine, but that's not the characteristic that was being discussed.

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on August 8, 2014 at 21:44:29
Cleantimestream
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 as you were... so shall you remain?

I do not know.



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

 

RE: I don't direct couple because I use filament bias. , posted on August 9, 2014 at 09:35:29
drlowmu
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 Hi Shane,

From my listening experiments, surprisingly, a two-stage DC amp sounds better with one supply, not two, and not two "stacked".

This single supply result is the opposite of all other amps I have built and listened to, where separate ( low DCR ) B+ supplies always sounded best.

The UBT-1 trannie is likely wound with 1,500 VDC insulated wire.

Jeff Medwin

 

RE: I don't direct couple because I use filament bias. , posted on August 9, 2014 at 17:27:19
shane.
Audiophile

Posts: 394
Location: S.A.
Joined: March 27, 2004
 Hi Jeff,

Just for reference, it was Mr Atwood who stated that the UBT1 was very marginal at ~510V and then only on condition that the secondary wasn't grounded and that the core was floated up to the voltage that the output stage was referenced to. He's the One Electron guy, so I take his word.

I'm sure there was probably some margin to his comment, and I guess it comes down to what you're comfortable with. In the end.. I'm happy with compromise.

 

Harmonics on the continuous tone are the least important, posted on August 10, 2014 at 14:26:54
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 to us in distinguishing say an oboe from a violin. Many experiments have been done clipping and attack from one instrument and on to the 'tone' of an entirely different instrument. People consistently use the attack to identify the instrument it was made by, not the tone and harmonics of the other instrument.

We pay more attention to an instrument's starting transients or attacks, and next to the decay.

The attack 'fully characterizes' an instrument.

Harmonics on the continuous tone come way third. And they don't happen with pianos and all other percussion, anyway.









Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: I don't direct couple because I use filament bias. , posted on September 9, 2014 at 11:58:32
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 I usually don't ground my secondaries.

Jeff

 

RE: I don't direct couple because I use filament bias. , posted on September 9, 2014 at 15:24:07
shane.
Audiophile

Posts: 394
Location: S.A.
Joined: March 27, 2004
 I like the idea of a fault current path in the event of a 3 stage DC meltdown !

MCB's here will shut it down in <0.3s, without the 0V reference the coil melts down in concert with the OPT.

Just not worth it.


Shane

 

RE: I don't direct couple because I use filament bias. , posted on November 2, 2014 at 08:54:52
horn kid
Audiophile

Posts: 128
Joined: November 2, 2014
 There are poor PP amps and poor SET amps.

There are top of the heap PP amps and top of the heap
SET amps.

My experience says the very best SET amps, used with a speaker that does not tax them heavily, are cleaner, clearer, more dynamic, and sound more like music than the very best PP. And that's not because they are "thick, tubey, colored, etc." I hear less of those colorations, just utter clarity, with the best SETs.

 

RE: Can sound cleaner but loses the magic midrange. , posted on November 6, 2014 at 14:05:08
Stuben
Audiophile

Posts: 669
Location: Guber Ohio
Joined: December 30, 2005
 Andy,

I built a Pentode SE input PP out IT topology. The ITs were Lundahl 1660s. I think the sound does maintain SE feel, the mid range is rich, with the nice tighter PP bass. I did run the OPT section cathodes to ground through the primaries of the OPTs....very nice additional damping.

Stuben

 

RE: push pull cancels 2nd order distortion so you will lose that fat warm sound of set, my push/pull 45..., posted on November 6, 2014 at 15:28:57
cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009
 "Yes, you are using the term differently. The discussion was about distortion created in the amplifier, not about the overtones contained in the program material. If you wish to call the overtones inherent to the source "distortion," that's fine, but that's not the characteristic that was being discussed."

There is also another reason why there is a huge distinction between overtones produced within a musical instrument itself, and harmonics (a.k.a. distortion) generated by the amplifier. The overtones produced by the piano when the A440 note is played affect only the timbre of the sound produced by the piano, by contributing 880Hz, 1320Hz, etc. as well.

By contrast, harmonic distortion in the amplifier will not only generate harmonics of the note played by the piano, and any other instruments in the recording but, crucially, it will also lead to intermodulation distortions between the notes and harmonics produced by the various instruments. The mess of intermodulation products is an inevitable and undesirable feature of any distortion by the amplifier, whether it be 2nd harmonic, 3rd harmonic, or anything else.

So it is indeed, as you say, inappropriate to blur the distinction between overtones produced by musical instruments and harmonic distortion produced by amplifiers. Overtones in the notes produced by the piano do not create intermodulation distortion in the concert hall when a violin is playing as well!

Chris

 

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