Just to circle back here, for general knowledge and posterity. First and foremost, Bakoon responded w/ THD <0.5% / SNR 95dB on their 13R. To paraphrase and extrapolate further, a zero negative feedback amp is not going to lend itself to the 'spec wars' you see from other manufacturers. The $200 SMSL SP200 advertises 0.00006% THD; achieving extreme distortion mitigation thru negative feedback is not an engineering feat per se, it is more a design decision which also happens to play quite favorably in marketing collateral. Some hear these amps as ultra clean, others may describe it as leaning towards sterile, lifeless. Not inherently bad at all, but this type of sound can start to feel rather homogeneous. Let's be honest, how different does a GSX2 sound compared to a HPA4, or even the new Topping A90? Sure, maybe a hair of variance but they're all underscored by that 'wire-with-gain' sentiment. They have little or no character, for better or worse. At the end of the day, and to oversimplify, a primary advantage of a zero global feedback circuit is increased musicality, air, holographic imaging and stage depth.. in other words, you get a solid state that gets you the closest to a tube sound without any actual drawbacks of tubes. If you need a more technical explanation, I'd advise you to check out some of Nelson Pass' articles on feedback and distortion. Some of his philosophies on amp design eschews technical perfection. So does Ayre and a few others. On paper their amps are more or less utter 'failures'. In practice many own and love their amps. Long story short, let your ears dictate sound quality, not graphs.
