I've been reading over on the Transcendent forum that a more "tubey" sound can be obtained by decreasing negative feedback. The message there, as elsewhere, is that NFB reduces distortion. Reducing NFB, goes the accompanying warning, accomplishes a pleasant (to some) tubey sound at the expense of increased distortion and, in the case of the Transcendent preamp, a compromise in the speedy responsiveness of the amp.
Yet elsewhere (e.g., UHF magazine's guide to hi fi, as well as this website: http://homepage.mac.com/tlinespeakers/vaughn/downloads/Damping-Factor.pdf )
there is a different perspective, which holds, in a nutshell, that NFB lowers distortion under conditions of a steady signal -- so that the amp performs well on specification tests, but that under conditions where the sound is not so steady but always changing (e.g., music), NFB actually has an undesirable impact on the music. The web article cited refers to "smearing" the sound, homogenizing it and generally sucking the soul out of it.
I'm a bit perplexed, and would be eager to hear some ... 'positive feedback' from the knowledgeable folks on this board.
I note that the ST70 uses 13 db of NFB. In the sphere of things is this a lot of negative feedback? Is it possible to improve the "sound" of these amps by reducing NFB at the expense of an increase in inaudible Harmonic distortion? (ok that last question has two parts).
Thanks for your thoughts.