Wednesday, December 14, 2011

And now, an early 1950s Stromberg Carlson AU34, but first the logo.

The earth, draped in sound. I can dig it.

Utilitarian beauty.

Top off so we can see what's under the hood. From lower left moving to far right: 6SJ7, 6SF5, 6N7 (doing phase splitter duties), a pair of 6L6 outputs & a 5U4 rectifier.

I baked this amp a few years back. It had been sitting in a damp basement and I wanted to insure the transformers did not contain moisture prior to my attempt at burn in. I want to say it went into red plate, or oscillation. The fact that I cannot recall pretty much nullifies all my prior attention. Looks like either the temperature was a touch high or there was some sort of residue on the metal.

Pretty rainbow colors.

Seems like another amp that predates twisted pairs. I guess it hails from the era in which low enough gain, or short enough bandwidth, made such steps unnecessary. I'll probably leave this one be, unless it proves problematic, unlike some others. Nothing remarkable here, though I do like the primitive (very DIY friendly) approach to tag board construction.

If this was a class, I would offer up this modified schematic (very thoughtful, thank you previous owner!) and the following picture and request theories as to what and why.

Aw, what the hell..


krivx said...

I don't know if I'm impressed or worried by the amount of valve amps you own.

how does the I/O work on this one? Can't make out any speaker or input connectors.

crochambeau said...

I think we'll be leaning on the "worried" angle before I'm done..

The original equipment is an F type microphone connector and a two lug screw terminal connector for phono input. There are two 1/4" instrument jacks as well, but I *think* those are post production.

Output is via an octal socket with different taps per pin.

krivx said...

F-type, like the co-ax connector? that must have been pretty cutting-edge at the time.

I'm planning on documenting the few amps I have lying around pretty soon. Octal sockets seem to get used for everything, I've seen them with matching inserts to connect different transformer taps for different mains voltages and speaker impedances.

crochambeau said...

D'oh! I think "F type" is misinformation on my part. 2501 connector, early threaded connector that could be considered a caveman F. Seen here:

crochambeau said... damn forums have made me forget to use my html..

krivx said...

The one here?

Looks like switchcraft still make these.

crochambeau said...

Yes, the one you linked, I was specifically aiming for this page:
The real link that will actually take you to the page about the 2501 connectors.

Narf! Apologies, I'm being incompetent today.