It's nearly perfect, ESPECIALLY through a straight 4x14 with Heritage Greenbacks. I like the 'Clean' side on the Green Channel A LOT better now. Front Board: I installed a 1M to ground on the wiper for VR3 (Red Channel gain knob), lowered C10 to.0022uf (no idea what that does where it is), removed R20 and jumpered (again, not exactly sure what that does), and removed C12 (bright cap across VR3.was a 470pf, might put in a.0047uf cap as that was nice when I tried it). Marshall Tube amp schematics, Hoffman amps tube amp schematic library Marshall Schematics. I did all that to get that first gain stage closer to a JCM 800 and/or 1959 lead schematic. ![]() Alright, here's where I am with this: Main Board: Removed C9 entirely (100pf from the first gain stage plate to the cathode) and replaced C12 (the first gain stage Ck, a 4uf electrolytic) with a.68uf Sozo and lowered the same stage's Ra (R13) from 220k to 100k while raising Rk (R14) from 1k8 to 2k7. ![]() I'm trying an altered version of the Joey Mods.pretty much identical, save for I'm going to run a.68uf cathode cap w/o the 1000pf plate cap on the first gain stage (he recommends a 1uf cathode cap with a 1000pf from plate to cathode, whereas I don't see that on your typical Marshall circuit so I'm rolling the.68uf alone to see if I can get good, true, lower-gain tones out of this thing.not so interested in high gain stuff). I have a JAN '80s 12AT7 and an older RCA cleartop 12AU7 ready to try in the PI, once I put my amp back together.
0 Comments
Leave a Reply. |