Jan Kok wrote: > 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?
positive half of the driver stage is just that way due to its simplicity. > 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? That's a push-pull arrangement. As the ripple is identical and both tubes have matched gain, the ripple noise cancels in the transformer. > Negative feedback would be my guess. And maybe those dual pentodes > were pretty well matched. For the modern equivalent, check out LM394 > SuperMatch Pair. Doesn't apply to me, but thank you. About the only thing well matching my front-end will do is minimize leakage current through the front-end protection diodes by making the inverting and non-inverting inputs have the exact same voltage level. It doesn't effect ripple leakage into the output for this circuit I have, unfortunately. > 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. It isn't coming from the input stage, but thank you for your comments. > I found some of the articles at http://sound.westhost.com/ interesting. > > Cheers, > - Jan -- "MOM, CAN I SET FIRE TO MY BED MATTRESS?" "No, Calvin." "CAN I RIDE MY TRICYCLE ON THE ROOF?" "No, Calvin." "Then can I have a cookie?" "No, Calvin." ("She's on to me.")
