picked up a 2000s fender custom vibrolux reverb amp for a song because the fella who owned it before tried to do "the fromel mods" on it and mucked up the pcbs (not hard to do anyway, but still a shame)
so i gutted it and rebuilt on eyelet board. normal channel is blonde bassman normal channel (with proper 350kB tapped treble pot thanks to weber). bright channel is blackface vibrolux but with 1uf first stage cathode bypass cap and 22nf off the plate (mini toggle switch throws a 1k5/25uf in parallel to add some more grit and low end). i've never liked how fender did the two channel amps with them being out of phase, so after tone stack recovery stages the channels are joined with a capacitive mixer and then onto the reverb (reverb in both channels plus can 'jump the channels' like an old marshall four holer). this amp came with 12ax7 phase inverter and no global negative feedback, i went with a proper 12at7 phase inverter and roughly blackface-spec nfb (used 1k resistor instead of 820r because that's what i had). trem is brown vibroverb bias vary instead of bothering with a roach. layout is super cramped because i started it before i even picked up the amp. while a bit of a pain to work on no negative sonic effects. next time i'll wait until i get proper measurements and make my life easier
tube chart scanned and updated to reflect the amp as it is now
PRR wrote:
Plotting loadlines is only for the truly desperate, or terminally bored.
from what I've read even stock these are very nice amps, albeit noisy. but i suppose no global negative feedback (why, fender?) will do that
it's going to a local guy who runs an all analog studio tomorrow when i drop off his 73 pro reverb (was blowing mains fuse and filament artificial center tap resistors. figured it would be an arced socket but ended up being a power tube with an internal plate-heater short. the other one tested bad for emissions anyway so it was time for new tubes)
PRR wrote:
Plotting loadlines is only for the truly desperate, or terminally bored.
