I'm restoring an RCA 63E 78rpm 3 tube phono. The original crystal cartridge is toast..I found a Sonotone ceramic that will work (although the fit is not the best), but needs more gain in the amp. I put a 33mfd cap across the 50L6 cathode, but still could use a little more gain. It uses a 12SQ7 as the input tube..Are there any substutes for the 12SQ7 that have a higher gain? I could add another pre-amp stage, but am trying to avoid that to keep it original as possible. Any ideas?

Hi Brian

Your ceramic cartridge puts out less voltage than the original crystal.

No higher gain tube with the same basing of 12SQ7. You could rewire the socket and use 12SH7, 12SJ7 or similar tube. If you need a separate diode for the radio circuit 12SF7 could be used.

Other than that you need more cartridge output. Could use a small, single transistor, amplifier?

Norm

:I'm restoring an RCA 63E 78rpm 3 tube phono. The original crystal cartridge is toast..I found a Sonotone ceramic that will work (although the fit is not the best), but needs more gain in the amp. I put a 33mfd cap across the 50L6 cathode, but still could use a little more gain. It uses a 12SQ7 as the input tube..Are there any substutes for the 12SQ7 that have a higher gain? I could add another pre-amp stage, but am trying to avoid that to keep it original as possible. Any ideas?
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Thanks for the suggestions Norm. You mentioned a single transistor circuit....Do you have an easy, adaptable pre-amp transistor circuit that I could use in these tube circuits? I run into this problem a lot, since I've been restoring a few of the old crystal cartridge phonos, and the modern ceramic cartridges are weaker on output.

If you post your E-mail address, I can send you a simple two transistor pre-amp circuit schematic that can be adapted to your phonograph. This is actually one from ED.

Brian, Norm, Warren,
For what its worth, had the same problem with an RCA 67V1 a couple years ago. Got the cheapest ceramic stereo cartridge I could find for my first experiment. Dissolved the plastic case with acetone, leaving only the ceramic elements, support structure and connector. Bridged the channels (mono), made a new light weight armature, and installed in original case using an original (NOS) stylus. I was able to get near orig output levels (approx 3.5 vpp) by toying with a resistive terminating/coupling network.

marv

:If you post your E-mail address, I can send you a simple two transistor pre-amp circuit schematic that can be adapted to your phonograph. This is actually one from ED.
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:If you post your E-mail address, I can send you a simple two transistor pre-amp circuit schematic that can be adapted to your phonograph. This is actually one from ED.

Thanks Warren---email cento366 at yahoo dot com
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