RIP David Manley

[philipbarrett]

One of audio's most respected designers and engineers passed away. It's a rare singularity who is equally recognized by both the home and professional markets for their outstanding designs. Condolences to Eve Ana and the rest of his family.

No more fitting than to post here a thoroughly irascible and enjoyable article he wrote in 1994;

http://positive-feedback.com/Issue65/manley.htm

[Chris A]

What a polemicist against single-ended tube designs...

I think some of what he wrote should be reproduced here, since it seems to resonate with PWK's audio philosophy, but also bring out other issues usually not discussed here - like size of rooms, ambient noise levels, and societal/nationality taste trends in music reproduction:

"Single-ended

We got this from very, very early days, plus, of course, from Japan, where it never really went away. Remember that these folks have a genuine fondness for horns from 98dB to well over 100dB/1 meter/1 watt. Remember too that they have small rooms, slender walls and generally a very over-crowded situation real-estate wise. Remember something else very important please, (and this relates to everywhere outside of America and especially includes Europe)... LOWER AMBIENT NOISE… EVERYWHERE! On streets, in airports (the people and PA systems, not the planes!), and especially in private homes. You think I've lost direction? No, it relates to power needed... add larger rooms, much higher ambient noise, less efficient speakers, a people who like (and who can afford) their music to be big, lifelike, and testicular, and you've just posted the funeral notice for single-ended topology. The word 'efficiency' crops up again in another context: the amount of clean power can you get from a very expensive (1000 to 1500 volts) power supply (plus DC on all tube heaters) coupling a single output tube through a necessarily very expensive and very inefficient output transformer ... IF you want it done right so the amplifier will produce full frequency response at full power bandwidth, the output transformer has to be 5 or more times the size of the equivalent push-pull type. As it gets bigger (because of necessary air-gaps in the iron) it gets costlier to take care of the upper extremities and retain the coupling needed for the lower extremities. Which is why the ones out there sound exactly how their response curves look - down 3 to 5 dBs at 30Hz and the same at 15KHz or worse, and all but wiped out at 20KHz and 20 Hz.

Yes, but, they say, just listen to the mid-range!! To which I say, "Sure the mid-range sounds good because that's all there is to hear" and "there's a whole lot more to real music than just midrange, boys."

Too, harmonic distortion can run inordinately high by the very nature of the single triode (look in the manuals; 5% isn't all that uncommon.)

(For the record, we do make to special order only, a no-holds-barred 75 watt single-ender that uses a 150 watt plate dissipation Russian triode, but I'm too embarrassed to mention the price.)

Push-pull topology (referring to the power output stage) has been the one of choice proven over years for a variety of reasons, efficiency being not least important. The very nature of push-pull topology with vacuum tubes provides worthwhile hum-bucking characteristics and also some of the even-order harmonic distortion cancellation advantages common to differential circuitry. Greater efficiency yet with lower distortion is available with fixed-bias designs to a factor of practically double that over those with self-bias cathode resistors (which must collapse as the tube gets past senility) plus, of course, the bias can be adjusted to suit individual tube's aging.

If the amplifier is to operate from an unbalanced source, a phase splitter becomes necessary to drive the output stages. A good high-current, self-balancing, low distortion phase splitter and input stage adds further to the efficiency of push-pull designs. Negative feedback applied in tasteful amounts combined with essential stage-by-stage linearity and superlative output transformers and power supply add up to make this a very hard topology to beat. (Again for the record: I like to make my own designs so that either single-phase or fully differential configuration is quickly available.)

If one is able to make the entire reproducing chain Fully-Differential (sources plus amplifier and preamplifier), we can more fully exploit the vacuum tube's unique propensity for total cancellation of even-order harmonic distortion and take advantage of the noise rejection available with common-mode implementation. But again, this design topology has to be done really right for its merits to outweigh its disadvantages... such as maintaining phase-to-phase amplitude constancy as components age. But I know for sure that the even-order harmonic distortion cancellation is a distinct boon (or more accurately a band-aid!) to some of the—ah, roughness, shall we say?—that we get for no extra charge from the early digital era we're unavoidably in.

Do you see the major contradiction or contra-indication I am highlighting here? No? Let me try again: A single-ended design constitutes exactly one half (or one phase only) of a fully differential topology. The absolutely known benefits of push-pull and fully differential designs in terms of distortion-cancellation seem to be diametrically opposed to those definite disbenefits of single-ended output configuration (popularly most liked, apparently, without any negative feedback). And a digital source will most likely magnify this, especially with less efficient speakers causing the single-ended amplifier to work hardest trying for realistic listening levels. Clearly it must come down to different people having totally disparate opinions of what constitutes good and correct sound..."

"Silly me: I've always thought real live music was the unwavering reference!"

[bracurrie]

What a polemicist against single-ended tube designs...

Have you no decency!? Discussing religion here could be taken as needlessly provactive.[:@]

But really its refreashing for us lowly inexperianced audio buffs to see not just the history of the technology but the eveloution of taste and its rationalization. I believe that the journey of discovery of audio tech is more than half the fun of this hobby. The pros have to be confident of their choices and only make changes for specific performance objectives. The home user can make choices, however ill advised they may be, as they learn, change and experiance an enjoyable journey of discovery. Either that or just listen to the music.

What was old is new again. Ain't it grand![]

[philipbarrett]

What was old is new again. Ain't it grand!

In the studio world I get a chuckle seeing gear we couldn't wait to boot out of the control room trading hands for 10x it's value on ebay. It's vintage so it must be good.

[Chris A]

Negative feedback applied in tasteful amounts combined with essential stage-by-stage linearity and superlative output transformers and power supply add up to make this a very hard topology to beat.

For the record, I believe we now know why moderate amounts of negative feedback don't sound like zero feedback amplifiers: Nelson Pass wrote on his tests using varying amounts of negative feedback on various amplifier designs and found that negative feedback produces higher-order harmonics that are more audible to human listeners than do lower-order even or odd harmonics that are present in large quantities using amplifier designs without negative feedback.

However, Pass also pointed out the the interaction of lower-order harmonics (even and odd) with each other produces "the elephant on the dance floor" effects during complex music reproduction, leading to an "opaque" sounding amplifier.

Chris

[Ski Bum]

My condolences to the Manley family.

I think those Japanese dudes were on to something.

[NOSValves]

What a polemicist against single-ended tube designs...

I think some of what he wrote should be reproduced here, since it seems to resonate with PWK's audio philosophy, but also bring out other issues usually not discussed here - like size of rooms, ambient noise levels, and societal/nationality taste trends in music reproduction:

"Single-ended

We got this from very, very early days, plus, of course, from Japan, where it never really went away. Remember that these folks have a genuine fondness for horns from 98dB to well over 100dB/1 meter/1 watt. Remember too that they have small rooms, slender walls and generally a very over-crowded situation real-estate wise. Remember something else very important please, (and this relates to everywhere outside of America and especially includes Europe)... LOWER AMBIENT NOISE… EVERYWHERE! On streets, in airports (the people and PA systems, not the planes!), and especially in private homes. You think I've lost direction? No, it relates to power needed... add larger rooms, much higher ambient noise, less efficient speakers, a people who like (and who can afford) their music to be big, lifelike, and testicular, and you've just posted the funeral notice for single-ended topology. The word 'efficiency' crops up again in another context: the amount of clean power can you get from a very expensive (1000 to 1500 volts) power supply (plus DC on all tube heaters) coupling a single output tube through a necessarily very expensive and very inefficient output transformer ... IF you want it done right so the amplifier will produce full frequency response at full power bandwidth, the output transformer has to be 5 or more times the size of the equivalent push-pull type. As it gets bigger (because of necessary air-gaps in the iron) it gets costlier to take care of the upper extremities and retain the coupling needed for the lower extremities. Which is why the ones out there sound exactly how their response curves look - down 3 to 5 dBs at 30Hz and the same at 15KHz or worse, and all but wiped out at 20KHz and 20 Hz.

Yes, but, they say, just listen to the mid-range!! To which I say, "Sure the mid-range sounds good because that's all there is to hear" and "there's a whole lot more to real music than just midrange, boys."

Too, harmonic distortion can run inordinately high by the very nature of the single triode (look in the manuals; 5% isn't all that uncommon.)

(For the record, we do make to special order only, a no-holds-barred 75 watt single-ender that uses a 150 watt plate dissipation Russian triode, but I'm too embarrassed to mention the price.)

Push-pull topology (referring to the power output stage) has been the one of choice proven over years for a variety of reasons, efficiency being not least important. The very nature of push-pull topology with vacuum tubes provides worthwhile hum-bucking characteristics and also some of the even-order harmonic distortion cancellation advantages common to differential circuitry. Greater efficiency yet with lower distortion is available with fixed-bias designs to a factor of practically double that over those with self-bias cathode resistors (which must collapse as the tube gets past senility) plus, of course, the bias can be adjusted to suit individual tube's aging.

If the amplifier is to operate from an unbalanced source, a phase splitter becomes necessary to drive the output stages. A good high-current, self-balancing, low distortion phase splitter and input stage adds further to the efficiency of push-pull designs. Negative feedback applied in tasteful amounts combined with essential stage-by-stage linearity and superlative output transformers and power supply add up to make this a very hard topology to beat. (Again for the record: I like to make my own designs so that either single-phase or fully differential configuration is quickly available.)

If one is able to make the entire reproducing chain Fully-Differential (sources plus amplifier and preamplifier), we can more fully exploit the vacuum tube's unique propensity for total cancellation of even-order harmonic distortion and take advantage of the noise rejection available with common-mode implementation. But again, this design topology has to be done really right for its merits to outweigh its disadvantages... such as maintaining phase-to-phase amplitude constancy as components age. But I know for sure that the even-order harmonic distortion cancellation is a distinct boon (or more accurately a band-aid!) to some of the—ah, roughness, shall we say?—that we get for no extra charge from the early digital era we're unavoidably in.

Do you see the major contradiction or contra-indication I am highlighting here? No? Let me try again: A single-ended design constitutes exactly one half (or one phase only) of a fully differential topology. The absolutely known benefits of push-pull and fully differential designs in terms of distortion-cancellation seem to be diametrically opposed to those definite disbenefits of single-ended output configuration (popularly most liked, apparently, without any negative feedback). And a digital source will most likely magnify this, especially with less efficient speakers causing the single-ended amplifier to work hardest trying for realistic listening levels. Clearly it must come down to different people having totally disparate opinions of what constitutes good and correct sound..."

"Silly me: I've always thought real live music was the unwavering reference!"

Its official I have a new hero! Indeed RIP David Manley!

[mikebse2a3]

A passage from David Manely's Vacuum Tube Logic Book

Elsewhere you have read our views on what smaller triode amplifiers can do for music. The people who will settle for triodes only,(this is the 'where' and 'why' part) are a select band of audiophiles who use very efficient loudspeakers (a necessary counter balance) and are found in the woodwork of Europe and Japan. Eschewing sub-woofers and megabuck-megaspeakers, they 'trip' on triodes, often as low as four and five watts worth, and will brook no argument about their preference. Are they wrong in their audio thinking? No not at all. Nobody is wrong in their desire to listen to their studied preferences, in our view. If we played you some Klipschorns being driven by gossamer-smooth triode amplifiers, you would probably be very agreeably surprised. Shaken, maybe. You might even want to own some.

You don't believe this is possible? Your favorite audio-dealer does not keep Klipschorns? We new that. You find it very hard to swallow that older technology can be good technology? Possibly even better technology? Don't bet big on it.

Just when some people assumed they knew the man..!!![]

RIP David Manley! Thanks for the music!

miketn

[Chris A]

If we played you some Klipschorns being driven by gossamer-smooth triode amplifiers, you would probably be very agreeably surprised. Shaken, maybe.

It seems to me that having single-ended design without having soft clipping occurring more or less regularly, and simultaneously having low second order harmonics as well as the absence of higher order harmonics due to negative feedback effects is a goal that we are looking for if we are trying to avoid non-linear amplification issues.

Push-pull tube amplifier designs provide a lot more opportunity to avoid these effects, as well as avoid the "room reverberation" effects from avoiding using very high efficiency loudspeakers with high output impedance amplifiers.

Current JFET amplifiers (single-ended or push-pull), when directly coupled to the hf compression driver of, say, the Jubilee K-402 horn in biamped mode, seems to be a better solution to this problem, IMHO. But using passive crossovers and driving even a 105 dB/W-M speaker such as the Khorn or Jubilee full range at concert level with one SET amplifier channel per loudspeaker will result in many more soft clipping events per unit of time using a single-ended amplifier design than if using the same relatively low-power amplifier in bi-amping or tri-amping mode driving the loudspeakers.

I really don't care for soft clipping or artificial room reverberation effects due to amplifier high output impedance: they make the sound mushy and muffled--to my ears.

Chris

[mikebse2a3]

Chris you might be surprised at the results if you heard these combinations..![]

First Watt F3 on one channel LF and HF vs Cary 2A3 p/p (LF) and Cary 2A3 se (HF) on other channel

[mikebse2a3]

or this battle of the amps

First Watt F3 on one channel LF and HF vs Cary 2A3 se on LF and HF of other channel

[mikebse2a3]

or how about Jubs fully driven by F3s

[mikebse2a3]

Push-pull tube amplifier designs provide a lot more opportunity to avoid these effects, as well as avoid the "room reverberation" effects from avoiding using very high efficiency loudspeakers with high output impedance amplifiers.

Push-Pull has challenges of splitting the signal and then summing everything back together in the transformer versus a single-ended design so it's not automatically a better approach regardless of the distortion measurements you mention. You should hear my 2A3 push-pull amp versus my 2A3 single ended amplifiers to understand that both design types if properly done can sound excellent and even very..very...close to the same in many respects!

As far as the "room reverberation effects" I just don't believe its an issue and the damping factor of the F3 (which is very low on it's own) isn't far removed from the single-ended designs you look down on....so if damping factor is what you want then many other designs can get you in the 100s or 1000s.. but don't be surprised if they prove to be a disappointment!

miketn

[Chris A]

so if damping factor is what you want then many other designs can get you in the 100s or 1000s.. but don't be surprised if they prove to be a disappointment!

I believe that if the ratio of the input impedance of the load to the output impedance of the amplifier channel is ~10, then things are good (which was also taught as a rule of thumb in my undergrad EE classes). Higher "damping factors" apparently don't buy you much more in further avoidance of room reverb effects while using very high efficiency loudspeakers. Mike, as you know, the F3's output impedance is stated to be 1 ohm, while the minimum input impedance of the TAD TD-4002 on a K-402 horn is about 11 ohms.

the single-ended designs you look down on

I'm using a single-ended design right now to drive the TADs (a First Watt F3) which is a single-ended/single-stage JFET amplifier design.

The problem that I have is with poorly designed and implemented single-ended triode amplifiers that have too little forward loop gain to do much about the very high harmonic distortion issues ("the elephant on the dance floor" per Pass), microphonics issues, high noise figures, soft clipping due to insufficient available power output capacity, constantly changing characteristics of the individual tubes, very limited operational tube lives, was well as the other enumerated issues that Manley described in the text that I quoted above.

Chris

[Chris A]

or how about Jubs fully driven by F3s

Mike,

Is there something that you'd like to share? I don't believe that I've seen anything from you on your auditions of these units. If you were waiting on an invitation from me to post them, you've got it.

Chris

[mikebse2a3]

The problem that I have is with poorly designed and implemented single-ended triode amplifiers that have too little forward loop gain to do much about the very high harmonic distortion issues ("the elephant on the dance floor" per Pass), microphonics issues, high noise figures, soft clipping due to insufficient available power output capacity, constantly changing characteristics of the individual tubes, very limited operational tube lives, was well as the other enumerated issues that Manley described in the text that I quoted above.

Chris

Chris did you read the Manley quote I posted above? How do you reconcile what at first appears to be opposite comments or is it easier to ignore Manely's comment I posted?

There are plenty of "poorly designed and implemented" amplifiers of all design types and they should be avoided but compare good designs of each type and things get very interesting and I will add that's when the real education begins..!

miketn

[mikebse2a3]

Is there something that you'd like to share? I don't believe that I've seen anything from you on your auditions of these units. If you were waiting on an invitation from me to post them, you've got it.

Chris

I could talk about the comparisons I've done but I doubt based on your almost constant posting against Triode SE designs that you would believe me.

I will say in the context of my system and my room I find that the First Watt F3 are excellent amplifiers.

Chris I truely wish you could hear these combinations first hand..!

All these amplifiers are a great example of how this very wise quote applies to our audio hobby:

Einstein: "Not everything that can be counted counts, and not everything that counts can be counted"

miketn

[Chris A]

I could talk about the comparisons I've done but I doubt based on your almost constant posting against Triode SE designs that you would believe me.

Try me--even folks like me can be convinced. []

Chris

[Marvel]

I could talk about the comparisons I've done but I doubt based on your almost constant posting against Triode SE designs that you would believe me.

Try me--even folks like me can be convinced.

Chris

You just need to hear some SETs that have output transformers that are larger than what comes out of an old telephone handset... []

Bruce

[seti]

High percentage nickel opt transformers with 50 triodes and mercury rectifiers is insanely good. Can't get that sound and feeling out of my head.