On 3/30/07, David Gravereaux <[EMAIL PROTECTED]> wrote: > Jan, I took your advice not to believe false positives. Yes, they do pop up. > But > I did find some noteworthy errors and discovered the driver stage had offset > gains > which resulted in higher thirds. Damn depletion modes don't come in enough > flavors :( And there is nothing I can do about PSU sensitivity 'cept for > regulating, which is good to know, none the less.
So why is PSU ripple getting into the output? I sort of remember old vacuum tube TVs (and amplifiers?) didn't use regulated supplies - just a C-L-C filter. How did they avoid hum? Negative feedback would be my guess. And maybe those dual pentodes were pretty well matched. For the modern equivalent, check out LM394 SuperMatch Pair. You might be able to replace load resistors in your input stage with constant current sources (TI REF200). That should eliminate any ripple getting into the input stage. I found some of the articles at http://sound.westhost.com/ interesting. Cheers, - Jan
