Aaron C

[Aaron C]

Hi there I'm new to this forum. I have a Capehart preamp that has a four pin power input lead. Wires are red, black, brown, and red. It has one tube, 6SC7, then it has a red and white in and out RCA leads. I want to hook this up to an Admiral amp Chasis that I have and works well. It has a similar jack to receive a similar Phono preamp plug but pins do not match up. On the amp, only three leads are wired up. On two I get 120 volts AC. The other is just a lead from one of those with a small cap in between. I don't know if my preamp should have AC current ran to it. Is the 6SC7 a recifier tube? I have photos of all of this. I imagine we can post photos on here as well. If there is anyone that can help I need it. Thanks. Aaron C. (919)-961-6688 call any time.

[pdf64]

Sorry, I don't know anything about either make but suspect that the power connectors for the Capehart and Admiral are incompatible.
The 6SC7 isn't a rectifier, rather it's a twin triode. I suspect that 2 wires are 6.3Vac for the 6SC7 heaters, the other 2 are B+ and ground to power the signal circuits.
Unless it's got a power transformer, the Capehart may not be abe to make any use of the 120Vac line, and might well be damaged by it.
Whereas the Admiral connector is a 120Vac line power supply and possibly a facility for a switch in the line, eg so that an on/off power switch on the pre-amp could also switch the Admiral on/off.
A tech may be able to modify them to enable them to work together, but I suspect that you may not have sufficient competence to undertake this yourself, bearing in mind the lethal potential involved.
Has the Admiral been modified so that it its properly grounded?

[Jazz P Bass]

"I have a Capehart preamp that has a four pin power input lead. Wires are red, black, brown, and red"

Here is a 'basic' tube preamp schematic.



Ignoring the fact that it utilizes a 12AX7 tube, it can plainly be seen that there are :
(1) two heater wires
(2) A B+ & a ground wire.
(3) A signal output wire.

What I would suggest is that you trace out the preamp & see where the connector wires go.

Here is the 6SC7 pinout diagram.



Pin 8 & 7 are the heater wires.
Pin 6 is Ground through a resistor.
Pin 2 & 5 are the plates B+ (high voltage through a resistor).