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I believe I've decided on my project! Can I get some critiques or thoughts?

A combo based on the AB763 blackface deluxe. One channel will be the standard 763 deluxe. The second will have some different values based off of a Two-Rock schem. that I have. I'll share them once I make the final decisions (there are a few others I'm considering). I'll have a toggle switch to choose between 22uf and 10uf cathode caps on the modded channel.

I'd like to get rid of the tremolo and use the reverb. This will take some more studying, haha.

Jensen P12Q 12" alinco speaker.

22"x18"x10" cab

What do you think???

Ok, here are the mods to the normal channel:

From the wiper of the volume (center terminal) to pin 7 of V1, there are a 220k and 470pf in parallel (Two-Rock).

From terminals one and two of the volume pot, add a 120pf cap (Dumble).

Cathode cap is switchable between 4.7uf (Two-Rock), 10uf (degooped Dumble), and 22uf (degooped Dumble/Fender).

Everything else stays the same.

Following the schematic, I traced the vibrato and reverb circuits on the layout tonight with highlighters. Vib. got pink and reverb got the yellow. I'm going to omit the vib. and try to make the reverb universal instead of just effecting the second channel.

Any ideas on making the reverb effect both channels? I can't really tell how it gets in there from the second channel.

Only a foldback reveb will get it for both channels. Not as much effect but its decent.

I do like your idea to combine both into one but including a rerb first try would be a challenge.

_________________
Stephen
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If the schematic I have is the AB763 (the other I have is AA763, so I assume this is it):
On the normal channel, after the post eq gain stage but right before the .47 cap after it, clip the connection and jump a wire to right before the .02 cap after which the signal is split between the reverb drive circuit and the additional vibrato channel gain stage. This will put both the reverb and vibrato (if you keep it) on both channels, and give you the extra gain stage. Also allows you to jumper channels without phase cancellation.

Bear

Thanks guys.

Bear, can you break it down a bit more for me? I am indeed using the AB763 schem.

On the normal channel, after the post eq gain stage but right before the .47 cap after it

Would this mean: from pin 6 of V1, connect to the 100k plate resistor as usual, then connect to a wire that runs off, then connect to the .047?

jump a wire to right before the .02 cap after which the signal is split between the reverb drive circuit and the additional vibrato channel gain stage.

Is this .02 the cap that runs to pin 1 of V5?

(I had been looking in a book where the schematic doesn't identify itself as the AB763, but I've since confirmed that it matches up with the other AB763 schematics on the web.

The layout I'm looking at has pin 6 of the first 7025 (tube 1) going to the .047 cap by connection "X". Snip before that cap. After pin 6 of the second 7025 (tube 2) there is a .02 cap. Jump to right before this cap. You'll notice that this after this cap the signal splits and feeds through the 500 pf cap to the first 12AT7 (tube 3) and also jumps from Z to Z under the board to one of the stages of the third 7025 (tube 4) to pump up the dry mix parallel to the reverb recovery stage.

Does that help?

Bear

Thanks, Bear. I do appreciate it. I'm going to do a graphic some time tonight to double check what you're describing. I've been working on a final for school all day today.

Bear, is this what you're describing? The caps solder to the same turrets as the plate resistors. Could I solder the wire to that turret as well?

Hmm. I'd think so, but I'm not sure. If I were modding an existing amp, I'd try alligator clipping it first.

Bear

Very cool. Thanks, Bear! Stephen, what do you think of this?

I was going over this one last time before deciding whether or not to go for it and realized something.

The V1b and V2b (pins 8 ) are linked together, so each tube is biased together. You can see that in the graphic above.

The V1a cathode (pin 3 ) is going to have a switchable cap value between 4.7uf, 10uf, and 22uf. Does that mean I need to separate the wire linking pin 8 to pin 8 of V2 and make pin 8 of V1 to match pin 3?