What makes a great amplifier?

[Arkless Electronics]

That is the job, but an amplifier can't be thought of in isolation, only in relation to the load it will be up against. Maybe there's a (somewhat tenuous) analogy to be made with what Mike Tyson said, about everybody having a plan until they're punched in the face. An amplifier design might be a straight wire with gain on paper, until it comes up against a real loudspeaker. That's when its character becomes apparent.

Hmm.. I see most seem to have been taken in by the "what load is it driving" thing... It's pretty unimportant in fact and when I design power amps I don't even give it any thought beyond safety of output devices etc.

 

[Arkless Electronics]

Wasn’t it Alan Shaw of Harbeth who said that any differences between similarly specified amplifiers were inaudible and put a pair of not inexpensive speakers on the line? AFAIK, no-one took him up on the challenge

I consider the sound of power amps crucial to the performance of a good system and that very, very few are good enough. To me it's as important as the differences between speakers once we are talking speakers that are at least pretty good. I'm amazed no one took him up on it... maybe they did and it wasn't reported!

 

[Ray]

Curious as to what others think make a great amplifier?

A great amplifier designer. They’re not that common.

 

[CJ14]

There is one problem apparently with push pull valve amplifiers that single ended amplifiers don’t have which was explained to me by someone who has designed his own transformers and valve amplifier. Apparently the metal used in even expensive amplifiers has non linearities in the output transformer B/H curve at low levels, this leads to higher distortion at lower levels similar to crossover distortion in transistor amplifiers. He kindly gave me the design for the transformers but because the metals are not standard the cost for a pair of output transformers is going to be over 1K as there is an MOQ of about 10Kg on the metal, I will probably get some of that back as he has promised to publish the design and the manufacturer has promised to reimburse me if he sells transformers using them. 1K is a lot of wedge for a couple of output transformers but a hobby is a hobby….

So ideally, the SET using valve would need to only use the centre part of the B/H curve of the transformer?
Could this be done in your opinion with a DC control winding that could force the transformer to be re-biased into the centre and still use a single tube/valve. ?
Then if this was "possible" could then design of the transformer with a built in sensor i.e. a Hall Effect Linear device to control the "re-biasing" winding but not follow the audio current and the changing B/H curve ?
This could be done like a DC servo system with good low pass filtering maybe ?
This would also mean the transformer would be smaller maybe?
It would also cost less, shorter winding wire less core maybe?
The control winding could be on one of the legs on a "E Core" with the "Hall" device in the other , thus helping to balance the magnetic field.

The other possible solution is to reverse the winding current in the Tube Anode winding faster, much faster than you maximin frequency so no high frequency is put into the tube or transformer, this I have done on smaller scale.
Using 1:100 transformer made by Sowter I manged to make a detector for low signals in the range of DC-1Hz to listen to the Earths plates. Designed it for a company in Scotland called "Ohm" so I had gain but only noise thermal type from the winding wires.

What are your thoughts? Russel.

 

[CJ14]

A great amplifier designer. They’re not that common.

Ray there a lots, but most are controlled , pushed down, bullied by marketing and sales/money men. And have no idea how good they could be if not restrained from meeting with others and buyers and hearing there thoughts, and then being forced to designs in a box designed by control freaks with no skills but power personalities.
Most of these poor sods work alone and are not allowed or have no interpersonal skills, to mix and bat ideas of each other, it is fun I had this with the many U.S. "design team's" I learned a lot and had fun, but best I enjoyed my work.
The one in the back room hidden from the world, like most secret weapons is not given is true value or potential. It is our world Money Money and keep these under paid under estimated slaves down, I have seen and experienced this it is wrong.

Sorry getting on my high Donkey again.

 

[tuga]

So ideally, the SET using valve would need to only use the centre part of the B/H curve of the transformer?
Could this be done in your opinion with a DC control winding that could force the transformer to be re-biased into the centre and still use a single tube/valve. ?
Then if this was "possible" could then design of the transformer with a built in sensor i.e. a Hall Effect Linear device to control the "re-biasing" winding but not follow the audio current and the changing B/H curve ?
This could be done like a DC servo system with good low pass filtering maybe ?
This would also mean the transformer would be smaller maybe?
It would also cost less, shorter winding wire less core maybe?
The control winding could be on one of the legs on a "E Core" with the "Hall" device in the other , thus helping to balance the magnetic field.

The other possible solution is to reverse the winding current in the Tube Anode winding faster, much faster than you maximin frequency so no high frequency is put into the tube or transformer, this I have done on smaller scale.
Using 1:100 transformer made by Sowter I manged to make a detector for low signals in the range of DC-1Hz to listen to the Earths plates. Designed it for a company in Scotland called "Ohm" so I had gain but only noise thermal type from the winding wires.

What are your thoughts? Russel.

In my layman view, SET amplification should only be used band-passed in an active configuration driving "real" horn speakers of very high sensitivity (~100dB or over). Paired with a standmounts (f.e. Leben & SHL5+s) they'll be clipping like crazy and putting out 3 or 10% THD and similar amounts of IMD.
By "real" horn speakers I mean 4- (+sub) or 5-way devices which produce constant narrow directivity down to the mid- or even low-bass, not a woofer in a bin box and 2" compression driver in a horn.
Something like this would work:

 

[Colin L]

That confines the use is SET’s to about 0.0000000000001% of the rooms / people on the planet. I’ve heard SET’s and big Avantgarde systems, dynamic, big, but coloured and they impose a false ambience to music which pales quite quickly. Plus of course mega bucks and they require a vast room.

 

[tuga]

That confines the use is SET’s to about 0.0000000000001% of the rooms / people on the planet. I’ve heard SET’s and big Avantgarde systems, dynamic, big, but coloured and they impose a false ambience to music which pales quite quickly. Plus of course mega bucks and they require a vast room.

Maybe the “false ambience” was coming from the horns.
To be fair the same could be said about omnis, or any speaker topology.

 

[CJ14]

You are a genius and a legend Colin. A proper designer and a gentleman to boot. Others would do well to take a leaf out of your book.

No NO that would be bad I am far to soft to be a business man and a few have walked all over me. They have to learn to be like Trump with skill not mouth plus other APPS . This people see us and think two a penny, but some will and do bite back.
It crazy set a company up to use the skills of somebody, so the company is based on his work then decide because you want total control and this can not get better (lack of imagination) the first design that was done is the only design the Donkey can. you need them not, so dump them, crazy.
I can think of three such disaster in my career, from MIH - Magnum, TOCA-SECA, TQ - what the hell is it name.?

Time now to bash some weeds as the rain has stopped.

 

[Tony L]

That confines the use is SET’s to about 0.0000000000001% of the rooms / people on the planet.

Yes, very much so. No one, no matter how much they like the topology, is arguing they are mass market. SETs have a context and the folk who like and buy them clearly understand it very well. I guess there is an ‘audiophile market bell curve’ with SETs at one extreme, seriously huge D’Agostino, Krell, MBL class A solid state amps at the other, and the majority of us ending up in some variation of the middle ground somewhere. Everything has its context and it is extraordinarily arrogant and condescending to assume the customer base of such kit doesn’t understand it perfectly well.

I tend to live in the vintage/classic market these days, but a very similar curve exists there too. It is nothing new as there have always be a remarkably diverse range of valid approaches to home audio. I’ve just as much respect for those lovingly rebuilding huge silver-face Pioneer and Marantz receivers, classic Naim, Krell etc, as folk like myself tinkering around with old valve amps and idler decks that are older than we are. It’s all good!

PS That’s obviously just the real audiophile market. The vast majority of modern consumer audio will be Chinese-made switch mode LSI crap stamped out on a single undocumented and unserviceable board in an integrated landfill-unfriendly plastic speaker/soundbar with a life-expectancy roughly 47 seconds longer than the warranty period…

 

[Dowser]

I’d also say synergy with the loudspeakers. Case in point would be my SE hybrid GM75 monos - best amp I have every heard…driving ESLs. Same amps fail miserably with, for instance, Sonus Faber Concertinos - with them I far preferred my ML No. 29.

 

[RoA]

PS That’s obviously just the real audiophile market. The vast majority of modern consumer audio will be Chinese-made switch mode LSI crap stamped out on a single undocumented and unserviceable board in an integrated landfill-unfriendly plastic speaker/soundbar with a life-expectancy roughly 47 seconds longer than the warranty period…

I better source replacements for the Formation Duo's now

 

[russel]

So ideally, the SET using valve would need to only use the centre part of the B/H curve of the transformer?
Could this be done in your opinion with a DC control winding that could force the transformer to be re-biased into the centre and still use a single tube/valve. ?
Then if this was "possible" could then design of the transformer with a built in sensor i.e. a Hall Effect Linear device to control the "re-biasing" winding but not follow the audio current and the changing B/H curve ?
This could be done like a DC servo system with good low pass filtering maybe ?
This would also mean the transformer would be smaller maybe?
It would also cost less, shorter winding wire less core maybe?
The control winding could be on one of the legs on a "E Core" with the "Hall" device in the other , thus helping to balance the magnetic field.

The other possible solution is to reverse the winding current in the Tube Anode winding faster, much faster than you maximin frequency so no high frequency is put into the tube or transformer, this I have done on smaller scale.
Using 1:100 transformer made by Sowter I manged to make a detector for low signals in the range of DC-1Hz to listen to the Earths plates. Designed it for a company in Scotland called "Ohm" so I had gain but only noise thermal type from the winding wires.

What are your thoughts? Russel.

no eye deer, I design solid state amplifiers as a hobby, I don’t have the time to learn the ins and outs of valves and transformer design.

 

[Arkless Electronics]

By far the cleverest and most intriguing single ended valve amp I know of (not triode) is the Pye Mozart. It's unique.

I'm amazed that the ideas it uses have not been taken on by others. My best guess there is that it's uniqueness means it would have to be redesigned from scratch, the full R & D program, as there's nothing similar out there and no knowledge pool extant on it. Specifically, the OPT would be the problem.

An 8WPC SE valve power amp the size of many pre amps that weighs bugger all and gives 0.2% THD and SS type damping factor.

 

[darrenyeats]

Apologies, I was going to add something about Walker as a designer as i didn’t want to suggest he was only slogans. Far from it, his designs are acknowledged and I’ve had and enjoyed many of them.

It’s the slogan itself and the way it is endlessly repeated that I was taking aim at. It might well be the ideal but it’s never reached is it, so the question is what compromises and decisions have been made along the way and what does the amplifier sound like as a result?

The maxim (however well-intended) could be misused to suggest there's only one kind of distortion.

For example as we know Jez has his views on NFB and distortion. We could just reply "straight wire with gain innit" and cause him to be enraged, or at least frustrated with our lack of comprehension again!

So, I think I get what you're saying.