NOS Dukane 1A395

[Phil_S]

Craigslist find today. Aside from a little dust, this thing came out of a time capsule. This is a Dukane PA, PP RCA 5881 tubes, Sylvania 12AT7, and RCA 5U4GA, rack mount chassis. The OT feeds 4z, 8z, 25v, and 70v. I purchased it from a retired "repairman" who found it on a shelf in his basement, having forgotten it was there. He said it was standard to carry a spare on the truck to swap while the customer's unit went to the shop. He says this one was never used. It came with the original box. He happily powered it up for me to prove it worked. The truth is, I would have preferred he didn't do that due to the age of the item, but I don't think any harm was done and he clearly knew what he was doing. In the process, he contributed a long 3-prong cord, but I don't like the spade lug connections, which incidentally appear to be the way this unit was meant to be hooked up (top pic, lower left). The vertical white tubes are resistors!

He asked, and I told him it was going to be a guitar amp. He asked me to let him know what I do with it and I thought that was really quite charming.

I'm not finding any date codes, but am thinking this model is from the 60's. I'll keep looking, maybe on the back side of the can caps.

So, the questions are:
1) Schematic anyone? I can probably get a SAMS from the library or trace it out. There are not a lot of parts. BTW, the big red caps are 400v 0.5mf. I can't see the markings on the can caps. I need to find my dental mirror.

2) Group think. What would you convert this to if it was yours?

[Koop]

What's up with the coffee cup in the left corner?

EDIT: Doh!! I see now, I'm looking right through the amp. The background color had me bamboozled.

[rp]

70V tap! Turn it into a tweed guitar amp and crank it through the school PA!

[Dr-Joned]

Keep it as is and build a multi channel preamp. One Fumble, one Wrack, and a Finger channel. Normally the old DuKane amps were meant to be driven with 1vrms on the input.

[Phil_S]

I admit to being caught inside the box on this one. Though I'm sure it's been done before, the multi preamp is pure genius. There's no sense tearing apart a perfectly good PA.

The 1V RMS is a curious point. I don't have a clear idea of the signal level in a typical guitar amp. How much will that need to be boosted? Assuming it needs a boost to 1V, what is the best way to boost the preamp signal to that level without making all wonky? Just insert a common gain stage/blender after the various preamps, and using what tube?

I'm really liking this idea, as the possibilities are almost endless. You think I can fit 3 preamps into a 17" x 6" chassis? When this is done, is a separate power supply built for the preamps? Are there potential ground loop issues? Separate boxes for pre and PA, this is new territory for me.

Thanks.

[Structo]

So this is a line level power amp?

Man, it's clean.

Good deal.