Flutter with 12au7 tubes...

[PlayItAll]

Hey all,

I have a 16 watt, single ended class A amp with one preamp tube and one power tube (like a poor man's Univalve). When I used a 12ax7 as the preamp tube, it runs nicely with good volume/gain and low noise. When I used a 12au7 it sounds really smooth BUT I am getting a soft sort of "flutter" noise in the background. It's not terrible, but enough to make recording at lower volumes a problem. I only have two 12au's - both old. One is an RCA and the other a Baldmin. Do I need to keep searching for a quiet 12au or is it more likely to be a circuitry issue with the amp?

Thanks!
Ed

[GlennW]

If you're looking for less gain a 5751 might help. It's my understanding that the 12AX7 and 12AU7 aren't completely interchangeable although many do it.

[PlayItAll]

Thanks, Glenn - I'll give that a try - also might try a 12ay. Time to buy more tubes! :-)