anyways, ive read how cesar diaz used bassman/super reverb output transformers in SRV's vibroverb so i put the jbl E130 in my super cab and man it sounds fantastic.
the tonequest report said something about 33 caps. now the aa763 vibroverb has .033 400v capacitor for the mids in the tonestack. the ab763 layout calls for a .047 400v cap for the mids. So im going to try it with both and see which one sounds better. ***8/20/14-i tried both caps in the mid section and with the .047 cap in the mid stack there was more of that strong bass. the .033 cap had just the right amount of bass and sounded way better for SRV tone so i stuck with the .033 cap. which is from the AA763 vibroverb. srv's vibroverb was AA763 in tonequest report, too.
the jbl E130 is an 8ohm and the output transformer is for a 2ohm but i was really suprised how awesome it sounds. i can always put the 4 10's back in but for now im leaving the E130 in because it sounds amazing.
also changing the two 68k input resistor on the vibrato channel to two 100k carbon comp input resistors was another thing diaz did that really takes the amp to the next level. it reduces some of the harsh high end. this is a very cool mod that helps alot if you play fast or play chords at gigging volumes. i love it. i do like the tone of the two 68k input resistor for single notes though, like for soloing, i get more saturation. id like to make a switch where i can go from the two 100k to the two 68k which would be nice.
*i must say if you convert a super reverb to a vibroverb and change the 100 ohm neg fdback loop to 47ohm then the 100k input resistors really help take off some of the harsh high end. the 47 ohm resistor makes the amp sound brighter.
anyways, if you havent tried it, give it a shot. when the blackface vibroverbs first came out, one of the reasons they werent liked was because of the small output transformer that sounded crappy (so ive read) the super reverb output tranny is huge and make a very sweet tone through a good classic 15 in speaker especially if youre going for a SRV sounding vibroverb.
it seems like the pulling v1 tube mod sounds better with the 100k input resisitors too. to me it does.
based on the tonequest report article about the srv vibroverb ive since added the other mods. including 100k input resistors and 47 ohm negative feedback resistor
*i also changed the few blue molded caps to NOS 715p .1 caps to match the picture of srv's amp. ive got it from a reliable source that diaz used 715p orange drops that were .1 and 1000-1200v. thats why they're so big. 715p are polypropylene which have more punchy bass and high end. the polyster ones are more midrange focused with a smoother top end so from what ive heard he didnt used those even though they are preferred by everyone generally.
*1 watt 100k plate load resistors for the reverb
(which is from a AA1069 silverface super reverb)
*"changed the 1M resistors in the phase inverter to a later 70's value for more clean headroom"
the only later 70's fender value that is not 1M in the phase inverter is 330k from a sf twin reverb and that would give more clean headroom.
*i read in AG that disconnecting the tremolo added alot of gain to the phase inverter so this might balance it out there i dont know. i did a 'before and after' with the tremolo disconnected and it sounded cleaner but with more sustain with the 330k and the disconnected tremolo. less muddied
I did the above mods and added a jbl E130, disconnected the tremolo, pulled v1 tube, solid state rectifier and you can hear how all of these mods work together to add more sustain but not be too distorted.
sounds great though.
the other mod Diaz did for SRV was putting 220uf 350v filter caps in place of the 70 uf ones. this made the tone stiffer in my amp. less compressed and there was less of the "tubey saturation" i didnt like it that much so i put my 100uf 350v filter caps back in there with the 20uf ones. This is definitely a Diaz SRV mod too and its even in the fender diaz modded 64 vibroverb custom.
when I first posted this I had a jbl d130 in my amp but recently got a jbl E130 and it sounds way better.
anyone with additions or corrections & ideas post for the rest of us!
also its fun to do this stuff to see what it sounds like so lets keep the comments positive. no naysayers
***I do this work myself and all of the mods are completely reversible so dont panic that im modding a blackface super reverb. i kept all the original parts which would only take 45 minutes to put back on
To much in a rush. Lesson learned the hard way. I will give a look see exam later today. Crap!!!!