Just added a D-style LNFB loop (22m-.047u/630v) to V1B of an ab763 Fender Vibroverb reissue, and noticed it gives a funny fizzy sound on startup & shutdown, almost like a bad tube... but I’ve tried multiple tubes, and it’s the same sound. Goes away when LNFB removed. Yes, the capacitor is on the plate end, and resistor on the grid... I’ve done this on other amps and never had this issue before, any takers??
EDIT: disregard, it was a lead dress issue... plate lead was crossing one of the grid resistors. Could've saved me an hour... figures!
LNFB noise on power up/down
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