Just wondering if anybody has had the same issue with their SVT-4. Was playing through Power Amp A only for some time into a single cabinet. One day I turned the amp on and it was really quiet. Switched over to Power Amp B and it’s fine. I’ve checked the stereo/mono modes, tried running bi-amp mode etc. I even plugged into the Effects loop returns for both PAA & PAB and am getting roughly the same result. Less noticeable without the preamp section, but still getting a volume drop. I guess my question is: Would a dead preamp tube still be the issue even though I’m bypassing the preamp when plugging directly into the effects loop? Or should I just take it to a tech? Thank you in advance.