stereo donor projects

[Luthierwnc]

Hi guys;

The soft economy seems to have dropped the bottom out of the tube donor chassis market. I'd like to hear if anyone has tried wiring a stereo amp back to mono for guitar use. Or, if you have put it in a two speaker cab with a line to each. I'm toying with a couple ideas right now but could be talked out of it.

Thanks, Skip

[Luthierwnc]

Anybody?

[dartanion]

You certainly can, or you can do something like the GA-78rv.

[Luthierwnc]

The Gibson is plan B right now. I'm experimenting with how to bring it back to mono. I don't know if you have ever heard the 78rv but it is a pretty cool amp. The one I heard had been hacked up for a 12 and a 10 but the guy pulled it off.

Thanks, Skip

[tubetek]

As a rule of thumb, look at the output tube compliment of the donor amp. If the amp has, for example, 2 channels with 2x EL84 (4 total) the power transformer can certainly handle a mono setup using 2 or 4 of the same tube. If you want a mono output, you would need to scrounge or purchase the appropriate output transformer. Select a schematic that matches the output tube compliment and hack away. Consider, however, that a stereo rig has some real benefits, especially if you use effects that have a stereo output (many delay-based effects, for instance) and would save you the purchase of the OT. Hope this helps. Is the prospective donor amp single-ended or push-pull?
Tom

[Luthierwnc]

I've already got lots of amps with new output iron. I'm mostly wondering if there is a way to do it with the originals. Thanks, sh

[tubetek]

IF the donor amp is push-pull, find a copy of the original Marshall JTM-100 schematic. They used 2 JTM-45 output transformers in a mono amp (using proper phasing of the windings) because that's what they had on hand. Study the output section wiring carefully; this setup will work if done properly. Also, over at www.18watt.com, a couple builders have used 2x 18 watt outputs in 36 watt builds. Hope this helps
Tom

[Luthierwnc]

Thanks, I'll check it out. sh