UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

adibrook · 28th Jul 2006, 9:29 pm

I'm still working on this power amp (formally the KT61 amp).

I finally found some power valves that i like. I have a pair of Mullard EL37's. I like them because they have a nice classic shape (unlike the el34) and they glow nicely.

I think they are suitable for use in this amp, and they look well on the shassis.

I'v ripped out all the old circuitry anyway, so i'll have to rebuild it to suite el37's.

The rectifier is a 5Z4G, which was originally in the amp. I also have a GZ32 and some other suitable replacements. The original 5Z4G is pretty well used.

The phase splitter is a 6SN7 in the usual confuguration (when one triode is grounded grid).

The only thing i'm not sure about is the 1st stage. I have an octal sockets fitted, and at the moment it's got a 6SJ7. But it doesnt look too good. It hardly glows.

I'v kind of changed my design philosophy abit. Instead of having lots of gain in one unit, i think that a better solutions is to have several units of moderate gain. This keeps feedback lower.

Does anyone know what i can use? Maybe even a single triode will be allright?

This amp will get use on stage at at least several shows, so i want it to look cool.

28th Jul 2006, 9:29 pm	#1
adibrook Retired Dormant Member Join Date: Dec 2004 Location: Weymouth, Dorset, UK. Posts: 377	power amp design I'm still working on this power amp (formally the KT61 amp). I finally found some power valves that i like. I have a pair of Mullard EL37's. I like them because they have a nice classic shape (unlike the el34) and they glow nicely. I think they are suitable for use in this amp, and they look well on the shassis. I'v ripped out all the old circuitry anyway, so i'll have to rebuild it to suite el37's. The rectifier is a 5Z4G, which was originally in the amp. I also have a GZ32 and some other suitable replacements. The original 5Z4G is pretty well used. The phase splitter is a 6SN7 in the usual confuguration (when one triode is grounded grid). The only thing i'm not sure about is the 1st stage. I have an octal sockets fitted, and at the moment it's got a 6SJ7. But it doesnt look too good. It hardly glows. I'v kind of changed my design philosophy abit. Instead of having lots of gain in one unit, i think that a better solutions is to have several units of moderate gain. This keeps feedback lower. Does anyone know what i can use? Maybe even a single triode will be allright? This amp will get use on stage at at least several shows, so i want it to look cool.