Help me diagnose my Sta-Level

Hmm...I've got a 12AT7 in mine. The socket is labeled the same. It's a just a lower gain version of a 12AX7 though, right?

And I did misread it. It's supposed to be the T.

That farting sound is clipping.  It sounds like analog-input and/or digital clipping to me.

One possibility is that it's inter-sample peaking.  Digital meters can only show you levels of the signal that they have sampled, however extremely fast transients can pop up and clip in between samples.  Since it takes some time for the circuit to settle down, you hear the residual stuff as clipping.

I get it occasionally from my preamps on certain signals, specifically DI guitar.  I don't see peaks but I can hear the same issues you are hearing.  Turning my preamp down helps considerably.  Sometimes I turn it down more than 12dB before the farting goes away.

Another possibility is that it's transformer overshoot, which is likely causing the intersample transients.

The Sta has an output of 600R, correct?  Is that going into a line-in?  Line-Ins usually have 10K-47K impedance.

Doing this you'll have some transformer ringing probably.  If you have one, try putting a small 600R pad on the output of the Sta to give it a load and see if it goes away.

Is that just like an in line pad? I'm getting rid of this passive di. It certainly does it less when I turn the pre down, but still seems to be there when the compressor hits a certain reduction point. The weird thing is that it doesn't seem to do it much with the single attack.

And matt, when you say "mine", you actually mean "John Kennedy's Sta that I stole from him", right?

Of course. And I would do it again, given the chance.

Concerning the attack times, you might want to check C-10 and C-11 to see if they have changed significantly from their values; also R-35. As for the unpredictability, it could be something as simple as badly oxidized, corroded, or loose fitting contacts in the tube sockets, particularly the 6386 or the 6AL5. Another thing to check is the 0B2 regulator tube which keeps the bias point from shifting. Check its' socket as well. Over time the sockets can lose tension with repeated tube changing and heat build-up. Bad solder joints can also be a problem if the Sta Level has been poorly serviced over the years. Properly maintained, the Sta Level is a rock solid device as evidenced by its' longevity in the broadcast business.

Harris9001 owns the best Sta I have ever heard. If you need yours looked at, John, I am sure he can do that for you. He is one of the best techs in Nashville.

R