Grateful Dead Music Forum

Hey all, I've got a question about a mod that maybe someone can help me with.

Just scored a '76 Silverface Twin with two E-120s. The guy I got it from got it from another guy in New York I'm pretty sure. The first guy had done some kind of mod, obviously with Jerry in mind. The right-most side of the back "control panel" has a single input with a knob next to it labeled "pwramp in". Basically a power amp input jack. Any idea what it's for or how I'd utilize it? Don't know much about electronics but I'd love to hear some ideas on how I could use it in the future?
(I don't know how to post pictures yet otherwise there would be one)

It’s “probably” a preamp tap. Jerry famously used a line out to a McIntosh mc2300 as a power amp.
If you’re not confident about the mods or the previous owner can’t clarify what’s going on specifically, I’d post some gut shots on here and/or take the amp to a reliable tech that can service the amp and fill you in the mods.

Poweramp In is the opposite of preamp out.

The latter is Jerry. The former would be to use the combo as a power and speaker box like if using a modeling unit that needs amplification.

strumminsix wrote: ↑Sat Sep 05, 2020 3:55 pm Poweramp In is the opposite of preamp out.

The latter is Jerry. The former would be to use the combo as a power and speaker box like if using a modeling unit that needs amplification.

That’s what I first thought of too. Then thinking about it, maybe it’s labeled in a way that, “this here jack ‘goes’ to a poweramp in? But that would be a very confusing way of labeling it, who knows, I highly doubt it. I would post picks to verify tho.

OsamaKeefe wrote: ↑Thu Sep 03, 2020 8:18 pmThe right-most side of the back "control panel" has a single input with a knob next to it labeled "pwramp in". Basically a power amp input jack.

I'd be surprised if this were not actually a preamp out, i.e., "run from this jack into the poweramp."

If it were literally a "run the power amp into here" jack, one of two things would happen: the power amp would go directly to the speaker(s), i.e., the jack is really a speaker(s) jack; you'd blow the crap out of the amp you're running into!

I've looked high and low and haven't found much on the subject. What I do find, I don't really understand I'm not in dire need of a solution, but I think it's an interesting thing that someone on here could make sense of. Plus, it sounds great as a combo, but if I could get a more Jerry-esque rig out of this (you know the type - Preamp, an expensive Mcintosh eBay find, and an even more expensive speaker cab) it sure would be neat. My logic is, I know all the parts necessary for a good Jerry rig. If I can kill two birds with one stone here utilizing this mod then I'll happily take it.