Agree. It woud be interesting to find any amp in rational price range that measured much lower distortion products, with same measurement eqipment. One might argue that if the measured noise is well below audibility maybe tne extended bandwith IS a plus given it sounds good? All engineering is trade off's. Not pontificating, just wondering...
I posted a couple of these in another thread, but there are definitely amps in a similar price tier to the STA-200 that exhibit substantially cleaner measured performance.
Cambridge 651W. Originally $1k, appears to still be available for $700 in a couple places. It's a Douglas Self 'blameless' design from what I understand, so it shouldn't be a surprise that it measures well.
http://www.htguide.com/forum/showth...xpensive-Cambridge-Audio-651W-Power-Amplifier
The Neurochrome Modulus amps. Maybe it's not fair to include these, but it does show what can be done on a relative budget if you prioritize measured performance. Even using the fully-assembled modules, you can build a low power 40/65W version for ~700 and a high power (220/300W) for ~1300 or so. Extremely good measured performance. Higher power modulus-686:
https://www.neurochrome.com/modulus-686/ . Lower power Modulus 86:
https://www.neurochrome.com/modulus-86/
Schitt Vidar. Based on the measured performance of their DACs, Schitt certainly doesn't seem to be a slave to 'good numbers', but the Vidar doesn't do too badly - it's probably the most directly comparable of these to the NuForce. - the FFT plot shows lots of low-frequency/power supply artifacts, and 2nd/3rd HD products are much higher than the other 2, but if I'm reading it right are still 20dB better than the NuForce. Potentially significantly, the Vidar HD products above 4th order seem to be completely absent, whereas with the NuForce there are clear HD products up to very high order.
http://www.htguide.com/forum/showthread.php?43904-Some-new-Schitt-in-power-amplifiers-the-Vidar
IMHO what concerns me about the STA-200 measurement aren't the actual THD+N numbers but instead the nature of the artifacts - lots of low-frequency hash, and rather high HD extending way out. It's entirely possible that these aren't directly audible by themselves, but with that much non-linearity present you have to think it's likely to show up somehow. I would actually accept the idea that a higher broad-based noise floor might well mask 'other problems' similar to how dither mitigates quantization artifacts, but it's harder to see how clear non-linearities might do the same.
I do think the question of amplifier audibility is a very interesting one though. I definitely agree that many specific attributes measured here probably have very low or zero impact on audibility until they reach a fairly high level (e.g. low-order HD which dominates THD, noise which is the other major part of THD+N) But OTOH amps CAN sound different, and IME they do so in relatively intangible ways that don't clearly map to conventional measurement metrics. i.e. for me it frequently tends to be perceived spatial presentation and 'body' which are frustratingly subjective in nature and probably relate more to channel matching than to any type of distortion product.
Still, I'm left feeling that since it seems to be relatively straightforward to make a good-measuring amp (or at least one that measures much better than the NuForce), shouldn't that be the minimum starting point? Even if there are other aspects that influence the subjective perception, it seems highly unlikely that bad measurements of this sort could actually be a good thing. But, I could easily be wrong, which is why I am rather interested in seeing more measurements and discussion around how they might impact audibility.
