Questions re:  GaNfet technology vs other designs.

Leo

What happened  to the Integrated Starkrimson?

What happened  to the Integrated Starkrimson?

@emil it got replaced by Starkrimson Streamer Ultra:

Don't forget to look at Peachtree.
 

Last, keep in mind, that many of these claims of distortion, at the levels of the amps in question causing tonal changes, has never, what 50 years later, be shown to be fully factual even though experiments are readily done.

@theaudioamp I see you dropped the idea that a GaNFET amplifier by virtue of GaNFETs must have load dependent frequency response. That's good- Occam's Razor wasn't supporting that idea at all. 

We seem to be seeing two messages from you- that harmonic distortion is and at the same time is not audible. If  you will set aside the handwaving for the time being, the ear's sensitivity to higher ordered harmonics has been known for a very long time- I refer you to the Radiotron Designer's Handbook, 3rd edition, published in the 1930s. The tonal effects of something like the 7th harmonic are easily explained in musical terms, for the obvious reason of the 7th having a very specific tonality with regard to the fundamental tone.

Regarding the effects of insufficient feedback, I refer you to Norman Crowhurst, who wrote about how feedback adds distortion of its own (including IMD) back in the late 1950s. At the time, no amp existed in which sufficient feedback could be applied, so he wrote about this in the context of all amplifiers. He also explains why: non-linearities at the feedback node. You can find his work on Pete Miller's reference book website.

Crowhurst's position on this topic is reinforced by that of Bruno Putzey's excellent article on the same topic. Seems to me I've referred you to that article before...

Finally, the tack we've taken over the years with our OTLs seems to have worked. FWIW they sound very much like our class D, which is to say quite neutral. From your comments it appears that you did not read the article at the link I provided.

@theaudioamp I see you dropped the idea that a GaNFET amplifier by virtue of GaNFETs must have load dependent frequency response. That's good- Occam's Razor wasn't supporting that idea at all. 

@atmasphere , I never ever said this. Not even close.

We seem to be seeing two messages from you- that harmonic distortion is and at the same time is not audible.

Also a gross misrepresentation of what I said.  I have been very clear.  Distortion is audible when a high enough level, end of story. I have also been clear that distortion is less detectable with music. I have also been clear that frequency plays into distortion audibility. There is no contradiction in anything I have said.

If  you will set aside the handwaving for the time being, the ear's sensitivity to higher ordered harmonics has been known for a very long time-

And the reasons also known, with perfect clarity for a very long time. Is there a point?

Regarding the effects of insufficient feedback, I refer you to Norman Crowhurst, who wrote about how feedback adds distortion of its own (including IMD) back in the late 1950s.

Do you have a point. You bring out this tired argument, it appears time and time again. No one disputes this is the case. However, you fail to provide evidence to support this is at all an issue. As noted, a quick perusal of Stereophile reviews and ASR shows most solid state amplifiers from the last several decades and certainly today having very low distortion out to 20KHz. You also ignored my very salient point that masking of lower order harmonics coupled with hearing degradation and the slope of Fletcher Munson curves means out past 4KHz, if not lower, higher order harmonic distortion becomes less of an issue.

w.r.t. Bruno, I will link his article here:  https://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf  which is a good dissertation on distortion and why negative feedback is good, which I am certainly not disputing, and which most SS amplifier vendors use enough of (as noted in measurements by Stereophile and ASR). Bruno does not talk a lot about audibility of distortion in this article. Mainly hand waving. He did make an off the cuff comment comparing linear amplifiers to Class-D and typical input stages off linear amps. This is why as engineers off the cuff statements should be avoided as most Purifi amps are front ended by just those same type of circuits buried in op-amps with enough feedback not to be an issue.

You know where Bruno spends a lot of time talking about distortion? Speaker drivers. it is also where he has stated he will spend his time, on speakers, specifically complete amp/speaker combinations. He acknowledges this is where most distortion lies.

I saw stated, and please correct me if I am wrong, that your OTL have output impedance in the 2-4 ohm range?  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. It is simply impossible. With typical dynamics speakers at 8 ohms and less, that is going to make a very noticeable change in the frequency response. I personally do not consider that neutral.