ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

The "other" tube

:

6/17/2000 1:36 PM

The "other" tube

Hi; I just bought an early '60s Epiphone EA-50 amp (schematic is in the Aspen book, p. 353). Now, I've been playing since '64 and I've had a '55 tweed Deluxe since 1968, but this little Epiphone is the nicest sounding tube amp I've ever owned. My question: looking at the schematic, I see that compared to my Deluxe, this amp seems to have an "extra" tube, and I'm wondering what it does. I'm not an electronics-head at all, but I know what a preamp tube (6EU7 in this amp -- odd, huh?) is vs. an output tube (2 6AQ5's) , and I know what the rectifier (6X4) does, but what does the "other" tube (the 6C4) do? Also note that these are not the standard amp tubes you see all the time. My tech says the power tubes were used in clock radios originally! Whatever, the amp is not loud, but it absolutely does not need any more controls than its on-off switch and volume control. Thanks!

6/17/2000 3:01 PM
FuchsAudio	A 6C4 is basically one half of a 12AX7. It could be used as an input preamp or as a phase splitter.

6/17/2000 4:35 PM
Steve M.	Andy, Don't you mean 12AU7? I believe that the 12AU7/6C4 were originally meant for phase splitters and/or cathode followers. Regards, Steve

6/17/2000 5:43 PM
Casey4s	The 6C4 is a medium MU single triode. In this application, it is used as a Phase Inverter (PI). Casey4s

6/17/2000 5:49 PM
Casey4s	By the way, the 6AQ5's are a much overlooked output tube, they were often used in space saving applications like car radios, and portable radios. They are elecronicaly equilevant to a 6V6 tube. I have a pair of these in a Fender Musicmaster Bass amp, and it has great tone for guitar. (but is a dudd as a bass amp) Casey4s

6/17/2000 7:46 PM
FuchsAudio	I thought it was closer to an AX than an AT, but I didn't check the book.

6/17/2000 11:42 PM
Graywater	Andy, 'Tis true - RCA Receiving Tube Manual refers the reader to the 12AU7 for curves when reviewing the 6C4. GW

Page 1 of 2