1940s RCA amp

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johnny7
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1940s RCA amp

Post by johnny7 » Fri Nov 29, 2013 5:44 pm

I came across an old RCA film projector and pulled this little tube amp out. It appears to be about 20 watts. The question is what shall I use it for?
What is the feasibility of converting it into a mic pre?
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Snarl 12/8
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Post by Snarl 12/8 » Fri Nov 29, 2013 5:53 pm

What would you use a 20 watt mic pre for? I'd go guitar amp with it.
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emrr
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Post by emrr » Sun Dec 01, 2013 10:40 pm

It's probably cathode biased, and more like 8-10W. Agreed, guitar amp. Not a good piece to consider for preamp use, but you can stick any old mic to grid transformer on the front end, load the output transformer resistively, and feed that to a recorder and find out. Practically not a mod at all.
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Darlington Pair
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Post by Darlington Pair » Tue Dec 03, 2013 7:19 am

I don't see an output transformer. Do you still have the projector, it's most likely mounted to the speaker because it's a field coil speaker.

Yeah, I'd say amp, I bet keys sound great through that thing too.

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Post by emrr » Tue Dec 03, 2013 12:18 pm

I think it's behind the 6L6's, you can see the some of the leads on the bottom shot.
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Darlington Pair
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Post by Darlington Pair » Tue Dec 03, 2013 1:55 pm

emrr wrote:I think it's behind the 6L6's, you can see the some of the leads on the bottom shot.
You might be right, I guess every time I see a four pin speaker jack I automatically think field coil, I didn't look for the leads coming through the chassis.

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