Questions re:  GaNfet technology vs other designs.

@theaudioamp Hm. On that basis we’re on the same page. Since you seem to think we are not, I’m disposed to think that you’ve not stated your position all that clearly in the past. There is also the issue of what is meant by ’when a high enough level’. IME that means well over 105dB down. Most amps can’t do that. The bit that I think gets ignored here is the fact that the ear uses the higher ordered harmonics to sense sound pressure, and due to a +130dB range is far more sensitive to them than most people think.

Now you are just making things up. This is as technically ludicrous as the CD demagnetizer someone reminded me of.

Let us unpack this fully. You are claiming that harmonic distortion 105 db below the fundamental is audible. Let us take an example of a 90db/watt efficient speaker, with 200 w/channel, what most would consider pretty loud. That is 90db/watt at the speaker. Let’s say 8 feet distance in a typical room.

• 6 db gain for 2 speakers
• 8db loss for listening distance
• 3db gain from reflections

Let’s ball park that at 110db peak at the listener and 113 db at the speaker. Sure you can get more efficient speakers and more wattage (be careful of real efficiency versus in-room), but most people would consider 200W/chan with 90db/watt as a setup loud.

Most people’s listening rooms that are not dedicated are probably 40db background, with some lucky to be 35db. Dedicated rooms you may get down to 25db with reasonable sound deadening. Keep in mind simply breathing is 10-20db. Now I realize this is broadband and the spectral energy is spread out and we can detect tones below the noise floor, but it still provides perspective. 105db on top of 25 is 130db (and we only have 110 at our disposal). Realistically you can probably hear down to a 0db tone around 3Khz in a really quiet room. That is a tone, in a really quiet room. I have to have at least a 105db primary tone, at say 300Hz, and that is going to mask a 0db tone at 3KHz.

But let’s go back to where we started. I have a primary, that is limited by my speakers to 110db, at the listening position, but you are claiming that a 5db harmonic is buried in there, that at 110db listening level is going to be heard. Really now? Do you want to walk that claim back a little? A harmonic 105db down is 0.0005% distortion from that harmonic. And you think this is audible in music? I am curious what playback device (speaker or headphone) you managed to do a test where you showed 0.0005% added distortion of a high level harmonics, in music, was audible, when the peak level was 110db to start. Why do I ask that? Because I want to buy those speakers or headphones as they are probably the lowest distorting ever made for home use. Even horn speakers at those levels have audible distortion in controlled circumstances, not to mention the masking and IM distortion induced by real music.

I would not expect anyone to take my word for this. Simply create a file with a single tone at any frequency you want, probably 200-300 Hz is best, then add in another tone 105db down anywhere you want and see if you can hear it. I would suggest about 2-3Khz.

Unless you have a speaker with a near flat impedance over frequency, it is impossible for that to sound neutral compared to a high damping factor amplifier.

This statement is simply false- we’ve compared exactly that side by side. I concede that you do have to be careful about the speaker that is being used. But it does not have to have a flat impedance curve! As I pointed out in the article to which I previously linked, the speaker needs to fall into the Power Paradigm of design rules (an example is a speaker designed to work with SETs, which have a similar output impedance to our OTLs).

My statement is absolutely true. Yours is not. I said it is impossible for your OTL amplifier to sound neutral compared to a high damping factor amplifier with any speaker that does not have a flat impedance curve.

Whether the speaker is designed to sound best (flattest) with a constant power, constant voltage of constant current does not make my statement incorrect.  A speaker designed for constant power delivery (uncommon these days) may sound better with your amplifier, but it will not sound the same as a high damping factor amplifier with that speaker. The two will sound much different and have a much different system level frequency response.  You will note I qualified with dynamic speakers of 8 ohms or less. A high impedance speaker will be less impacted by the output impedance of the amplifier obviously.

At a basic level, with your high output impedance OTL amp and a high damping factor amp, with any speaker with a typical varying input impedance, no matter the design rules, it will become almost impossible to level match such that you can even do a proper A/B comparison as the frequency response of the system will be so different.  We are dealing with basic electrical parameters here that cannot be simply had waved away.

My statement is absolutely true. Yours is not. I said it is impossible for your OTL amplifier to sound neutral compared to a high damping factor amplifier with any speaker that does not have a flat impedance curve.

And the fact of the matter that given the right speaker which may or may not have a flat impedance curve the OTLs can sound perfectly neutral (and to be clear those speakers are the exception rather than the rule). Just FWIW, I have the advantage of you on this point- we make an amplifier that has an output impedance that's difficult to measure and we can compare it to our OTLs and do so on a daily basis. Clearly you didn't read the article at the link I posted. Maybe you should. Or not... Tempest in a teapot, that sort of thing 😁

Let us unpack this fully. You are claiming that harmonic distortion 105 db below the fundamental is audible. Let us take an example of a 90db/watt efficient speaker, with 200 w/channel, what most would consider pretty loud. That is 90db/watt at the speaker. Let’s say 8 feet distance in a typical room.

Ever hear a system that sounds loud? If you work to really get rid of those pesky higher orders, you'll find that even at high sound pressure levels on a meter that the system no longer sounds 'loud'.

Put another way the sign of a good system is that it does not sound loud at any volume- it will always have a relaxed character. What you are forgetting is the ear converts distortion to tonality and it also perceived higher orders as loudness. This is why SETs can sound so 'dynamic' and its the source of brightness in most transistor amps. Easy to demo, FWIW... and is also why the right measurements on paper have a directly line to our listening experience (and likely why most of the time they are either not made or not published; I think the industry really wouldn't like people knowing what equipment sounds like by looking at the measurements...)

Its funny how so many people think the ear stops using its perceptual rules beyond an arbitrary point on a bit of paper.

@atmasphere you are twisting my words to attempt to win an argument. Clearly I said your OTL amplifier cannot be neutral compared to a high damping factor amplifier. You have said nothing that disproves that.

For your other amplifier, are you saying it is difficult to measure because it is low? And you are claiming it sounds "the same" as your OTL amp? I don’t believe you if that is the case. I am sure I could find some high impedance speakers where it may, but for most dynamic speakers, that just will not be the case. The frequency response variations are unavoidably large. In casual listening, you may convince yourself they are similar, in critical listening, they will not be.

Ever hear a system that sounds loud? If you work to really get rid of those pesky higher orders, you’ll find that even at high sound pressure levels on a meter that the system no longer sounds ’loud’.

I see no point in this post. Though I am almost always in ear plugs, I have done enough with pro-audio to know loud. Does it sound loud. Of course it does, even if the distortion is low, but it 0.5% low, which with music is inaudible.

You said that a harmonic 0.0005% down is audible. That is a 5db tone with a 110db primary frequency peak at the listening position. I really should clarify more. That is a 5db tone, when in addition to the 110db primary tone (the limits of our system and most people’s systems), that any non electronic music already has a ton of natural distortion that will itself mask electronic distortion including higher harmonics as the natural higher harmonics will mask other induced harmonics. This is one of the reasons why it is so hard to detect additional distortion in real music as there is already so much natural distortion.

Saying that "loud" is possible does not negate the lack of viability of what you have claimed. Put another way, it does not matter if it is SET or any other technology. You are starting with a conclusion and trying to work back toward a reason without showing the conclusion is true let alone viable.

Its funny how so many people think the ear stops using its perceptual rules beyond an arbitrary point on a bit of paper.

It is funny how many people arbitrarily make claims that cannot be backed up with demonstrations, but worse, are outside the realm of possibility.  I didn't even call you on the fact you said well over 105db down, I gave you the benefit of 105db down. Well down to most would mean another 10 or 20db lower.