Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bonzerinc on August 09, 2015, 06:13:28 pm
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Hey y'all-
I've started working on a 2 channel AB763, and was wondering what speaker set-up to use, when I thought of my old Peavey Vintage. It's got four 10-inch speakers at 4 ohms and a reverb tank, so that's well on the way to a Super Reverb (it really wants to be a Bassman, but too bad). I would like to make minimal changes to the amp, so I'm trying to mimic the old chassis as much as possible. If I want to go back to stock Peavey, it'll be a trivial matter of switching out chassis. At 20 ½ x 4 3/8 x 2 ½ inches, the Peavey chassis is MUCH smaller than a BF/SF, and I'm wondering if I'm trying to pack things too tight. I've enclosed a diagram which shows the reverb sends and returns at one side of the amp, rather than in the middle. That's purely so I don't have to alter the existing reverb tank leads. However, it moves the pre tubes closer to the transformers. As long as I'm using up that space, might as well put the footswitches there, too.
The board is shown in light grey. The darker grey components are on top of the chassis, and the first 2 filter caps would be inside the chassis on a terminal strip that is mounted on the same bolts as the choke. The other 3 filter caps are along the board, under the pots. On the front faceplate, I've got mid knobs on both channels, though I'm not sure I'll end up doing that. I only have a single input, then will have a channel select to go normal, reverb, or jumped.
What do you think? Am I crowding things too much? Should I reposition the reverb jacks and footswitches? Do the tubes and transformers have enough room? Do trees moving make the wind blow?
Thanks,
Michael Bonner
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Are the tubes on the back panel?
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I cropped off the end flaps trying to get the image as small as possible. Probably shouldn't have done that, since it makes it harder to see the chassis layout. The knobs are on the top of the amp, pointing to the ceiling. The tubes are pointing down toward the ground, and the transformers stick out toward the front of the amp. There is no back panel - that's the open face of the chassis, which will be covered up by the top rear panel of the cabinet. Like a tweed Deluxe.
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It will be very crowded. In fact, you'll have to plan very, very carefully. Build it in layers. If you can make a board that is 2.5" wide you'll make life a little easier. I built a single channel with reverb only in a 3 x 4 x 17 chassis and stuffed it in a Tweed Deluxe cab. It was quite a challenge!
As for your basic layout... I'd move the 4 phono jacks close to the reverb transformer. And I'd move the input jack/selector as far away from the power switch as possible. See attached pic.
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Oops. I got the front almost entirely backwards.
You have the reverb driver square with the tubes, whereas I usually see it turned at an angle. Is that important? Having it square would make it easier to position the footswitch jacks, but there is room to angle it if I move V1-3 as far over as possible.
I've been playing with a cardboard mock-up of the chassis, and it really is tight. I'm going to keep working toward this, but will also work up a Plan B, just in case.
Thanks for your help!