Why Don't We See More High Current Electronics?

Here's one more for you:

http://www.atma-sphere.com/papers/paradigm_paper2.html

Why not ask what the relationship is between doubling power and how your ear/brain system hears? The short answer is that you get flatter frequency response, but only with certain speakers. This comes with a price- distortions that the ear is extremely sensitive to. The ear hears these distortions as a variation (coloration) in frequency response! So in a way, you can't win with the explanation of flat frequency response.

The actual fact of the matter is that if you want the equipment to sound like real music (which IMO is the goal of any high end audio system) than some of the design parameters that bring you the ability to double power as impedance is halved may have to be abandoned. So you are seeing that occur, for example there are more manufacturers here in the US of vacuum tube audio products than there was in 1958!

Peterayer, we agree on that- all the system can do is reproduce the recording as accurately as possible.

Yes- audio equipment does not care what kind of music you play on it.

An amp with a low output impedance does not have a frequency response that varies with a speaker's impedance.

That depends on how the speaker is designed. Take a look at
http://www.atma-sphere.com/papers/paradigm_paper2.html

An excellent example is a Sound Lab ESL, but by no means the only example. You can also run into frequency response variation with highly reactive speakers (high efficiency). You have to look at the intention of the designer of the speaker.

Yeah, we've had this discussion before. Same old same old. Lots of assertions, but no supporting data. Negative feedback is bad because it causes time-domain distortion, distortions we can measure aren't important

Of course there is plenty of supporting data, and the distortions we are talking about *can* be measured, as well as heard.

high output impedance doesn't really affect frequency response linearity.

I don't know where you got that but you did not hear that from me. In fact the whole point of that paper (which now I am guessing you did not read) is that you have to **pay attention** to these things to **prevent** errors in 'frequency response linearity'.

so very high current amps are mostly for people that have more money than sense (like me).

Tube amps are for people even more skewed towards money than sense. ;-)

So, are you saying here that you have a tube amp in your future?? :)

The first is simply the lack of citation of any historical or scholarly references, or measurement data. This need not be . . . I think that Atmasphere could actually support his design choices much better by a properly researched, documented, and peer-reviewed paper on the subject.

Kirkus, thanks for your comments. I can produce a lot of data on this, but FWIW the paper I have often linked to is designed to be easy to read, and also easily understood by someone who does not want to go through mathematical proofs that they may well not care about. However I take your point so perhaps a second document that is a bit more in-depth?

The second is the interchangability of pespectives on amplifier output power ratings, output impedance, and circuit design, specifically the use of negative feedback. Obviously, Atmasphere prefers Class A OTL designs with little loop feedback . . . and the consequences are very poor power efficiency and a high output impedance, both of which are key factors in the rated power outputs of Atmasphere amplifiers.

I should clear something up here. Yes, this paper is on our site but it does not specifically point to our gear as the solution. I see this as a bigger issue! I have had a few people accuse me of making this stuff up- what I suggest to them is use Google to look for older Fisher amplifiers with the variable damping control (it has a spot on the dial labeled 'constant power').

I don't go for feedback simply because I've never seen it sound right (I use master recordings as a reference FWIW). Audiophiles are always looking for that 'difference' in gear that is responsible for it sounding like music rather than electronics. I have run into plenty of info on the subject, from such luminaries in the industry as Norman Crowhurst and Nelson Pass and it seems redundant on my part to restate that which has been part of the lexicon now for over 50 years.

The wholly illogical part is the inherent value judgement against amplifiers that have clipping-power-versus-impedance characteristics that are different from Atmaspheres'. Because an examination of this data gives ZERO information about how much current an amplifier will produce, what its output impedance is, or the amplitude of any distortion products in its output.

Again, this is not just about the amplifiers with which I am associated. You will find similar characteristics in SETs and P-P tube amps that feature little or no feedback. Contrast that against the Wolcott, a tube amplifier that behaves as a Voltage source, and the point is made in better contrast. But there are SS examples of zero feedback designs which I have often mentioned and admire.

With regards to why I eschew loop negative feedback, which I regard as a crucial issue, to restate myself: feedback adds odd-ordered harmonic distortion to nearly any (traditional) tube or transistor design and it is very easy to prove that our ears use odd orders to determine the volume of a sound (I can provide a simple test scenario that almost anyone with test equipment can perform to prove this). Essentially, a fundamental rule of human hearing is being violated in order to reduce (apparent) distortion on paper and to reduce output impedance. Its not coincidence that feedback affects distortion the way its does and we are able to hear its effects the way we do.

Regarding distortion, FWIW our gear makes primarily the 3rd harmonic and is absent of the even orders on account of cancellation throughout the circuit, due to its fully differential topology.

Now I think it is understood that I prefer tubes, but the truth of the matter is I would rather work with transistors. They are a lot less work to build than a good tube amp! So far I've not got transistors to sound right, and I have yet to hear a transistor amp that does. Being in the industry, I've had plenty of opportunity to hear a lot of amps- it comes with the territory. We can write that off to preferences, but there is enough standing evidence and literature to the contrary (IOW, that there is more to it than preferences) without *my* input.

Foster_9, I think there was a typo in your last question- the input impedance you are looking for is 50K ohms (50,000 ohms) or 100K ohms.

Most transistor amps, FWIW, seem to be closer to 10,000 ohms input.

Here's my vote: a zero-feedback transistor amp that behaves as a voltage source, from Ayre.

http://www.ayre.com/mxr_details.htm

Input impedance is very high- any preamp will work with it.

Irvrobinson, he wants something that doubles power as you cut the load impedance in half. But I don't like feedback (human hearing perceptual rules meow meow...)...

Atmasphere, technically there is no such thing as no feedback in an electrical circuit and hence a zero feedback amplifier, can you quantify your statement ?

Loop negative feedback is what I was referring to. I have no issues with degenerative feedback as it occurs in real time.

Foster_9, with traditional SS amplifiers using feedback and operating class AB, you are not going to find a lot of difference in the sound. So older amplifiers are indeed an option, but making sure the electrolytic caps that occur in the circuitry are actually good will be important. In this regard the HK Citation 11 and 16 were decent amplifiers- sounding very much like many modern amps for a fraction of the cost. But you had better know a technician that can service them out, as their filter caps will be shot by now.

Another amp that seems to stand out is the BEL amplifier. It was a well-made amplifier whose designer died too soon.