Solid State Guitar Amp Forum | DIY Guitar Amplifiers
Solid State Amplifiers => Tubes and Hybrids => Topic started by: slideman82 on February 23, 2010, 11:15:51 PM
Hi! I want to fix a problem in a friend's Vox AD 50, it seems that oscillates with distorted amplifier emulations at max gain, master volume and PA gain pot... also sound gets noisy after a few minutes of hard playing. Can I do anything to solve this? Maybe changing output IC? A power amp schematic would help me a lot!
MODS? Pretty easy... just replace 12AX7 for a high quality NOS 12AU7 and 2200 uF caps for 4700... tone improvement! Really awesome!
Hi slideman.
From what you say, maxing *everything* and using highest gain emulations, I'd be surprised by it *not* oscillating.
Even real Marshalls do.
It's hardly a power chip problem, rather an excessive gain preamp, used full tilt.
Going from "X" to "U" will certainly lower the gain a lot, and tame the beast.
Duplicating power supply filtering, specially if skimpy to begin with, is always a good improvement.
Thanks, anyway! I'll improve filtering. and probably add other cooler. Heatsink it's not quite big, and maybe I'll change it later...
This amp is what I call a "toy amp". It has some noise gate effect that't can't be switched off, and this removes some of the amp's dynamics (not too much sustain).
I'll see what I can do, I already have a AD30 schematic, it's the same but with dual 30V DC supply instead of 40.