As you rightly point out, misapplied feedback can actually make things worse in an amp that was behaving well prior to its introduction. This is certainly true of the Williamson and any other design that has too many coupling caps in the loop and/or has an OP tranny with deficiencies such as excessive leakage inductance.Example: you can have an amplifier perfectly flat from 20Hz to 20kHz, but if there's any phase error at the ends, you won't see it until NFB kicks it in the middle anatomy and it gets red and swollen.
Incidentally, I wonder why Mr. Williamson designed a global FB loop in his amp, when he was using triode OP tubes?[/B]
Miles Prower said:Problems such as these can only be treated empirically. You won't actually know if it will be a problem until you have the amp built and running, as it depends on so many factors that you can't know ahead of time.
Phase shifts can be and should be addressed during the design stage.
People seem to keep wanting to slug the frequency response of the input stage to make it the dominant pole
amperex said:Tune with changing to different manufacture tubes called tube rolling. A search can find upper half of noted best quality tubes worthy of auditioning.
Changing low grade coupling caps from say a nasty Sprague orange drop to an AuriCap or more expensive capacitors brings good results.
If you believe in spending money for better percieved quality, yes.
Also assumes all the advertised products work as well in your particular amplifier as claimed, which come to think of it is suprisingly lacking, in contrast to the usual attitude of "your amp may vary".