• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

What tubes for 7K6PP X-former

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I have started a project that was planned to end up as a PP-amp with triodes 50CA10. Transformers (all), chassis and some components are in place. I also had 4 tubes - 50CA10 - but now only 2 are working and it appears to cost me an arm and a kidney to get new ones, so ....

... considering what I have:
OP-transformers CXPP25-MS-7.6K
Mains transformer HE NT-8466 ,
what other kind of tubes (preferable odd kind of) could replace my 50CA10?
I have a bunch of 6L6, that could work, as well as 807. As I have made holes in the chassi for the 50CA10 (octal fits perfectly) and for two noval I really want to stick to tubes that fit in here (as much as possible), which rules out odd stuff like 829.

Here's the box:
An externally hosted image should be here but it was not working when we last tested it.
I note that on the datasheet I found for the 6CA10 (same tube, just 6.3v heater), that the plate curves are listed as BOTH 6CA10 AND 6JE6.

This means, most likely, that you could put in 6JE6s or 6LQ6 (interchangeable with 6JE6) and not change the operating point of the circuit, except for heater voltage. Of course, you'd need to install Novar 9 pin sockets and plate caps...

Joined 2004
Paid Member
Other ones to look at are the 6CK4 and 6AH4 - these both work well with plate to plate loads in this range. They're inexpensive, quite linear and the amplifier I designed and built years ago using 6CK4 sounded pretty good. (The cross coupled differential driver circuit though was not the best choice for driving the significant miller capacitance of a power triode.)

A quick look at the 6CK4 data sheet indicates the "El Cheapo" splitter/driver lacks sufficient gain and that AB2 operation might be feasible.

A Mullard circuit using a 6AB4 voltage amplifier and an ECC99 LTP should provide plenty of voltage swing, while "laughing" at the Miller capacitance of the "finals". If AB2 is used, buffer the LTP with IRFBC20 MOSFETs DC coupled to the 6CK4 grids.
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.