el34 champ

[bigsmitty]

what mods are needed to run el34 in champ?

[Phil_S]

For starters you'll need to know if the filament winding can support the EL34. One 6V6 needs .45A, and one EL34 needs 1.5A.

Beyond that, you'll want to get a different ouput transformer, as the plate impedance to speaker match is wrong. Also, the one for the 6V6 likely doesn't have capacity for the power, which is about 8W for the EL34 compared to 4.5W for the 6V6.

Back to the PT, the EL34 will draw about twice the current of the 6V6 on the B+ rail. So, even if your PT will take care of the filament problem, will it supply adequate current on the B+ rail?

Then you'll need to change the cathode bias resistor from 470 to around 1K ohms.

By the time you buy a new PT and a new OT, you might as well build another amp. The champ doesn't have a lot of parts, so it's a quick build.

[Andy Le Blanc]

A champ PT has a heater winding that's rated around 2A, you should be OK there.
But the high voltage winding is only rated at around 70 ma. so no matter what
you do that will be the biggest limiting factor. The New Sensor champ OPT
comes with a paper that says its a 7k primary 4ohm secondary 20w tranny.
So if you were to be careful not to bias your EL34 over say 45ma it might
hold up, but its not gonna get the best performance from the tube or the amp.
The figure that missing here is a max dc bias for champ OPT. You'd be better off
replacing the stock OPT with say a Hammond universal 125D or 125E so that
you can play with what you got without melting the wax out of you champ
and have a selection of primary impedances to experiment with within the
confines of your available power supply.

[dartanion]

Allen Amps has Heyboer made iron for this purpose exactly. I did an EL34 version of a 5E1/5F1 with these and it sounds great.

[Allynmey]

Do a search for the Beast build I did. Mark Huss also did one and they all originated with Richie Halls idea. He is currently on Beast 2.

[dartanion]

The Beast is a great amp. Richie designed a winner there! They're a really screamer.

[CaseyJones]

If you're talking about using an EL34 in a stock Champ... DON'T DO IT!! The stock Fender PT is wimpy wimpy wimpy, it will make a sound like a Fry-o-lator as it urps its guts out. If it has anything left after that it will go up in smoke...

If you're building a clone start with a tweed Deluxe PT or even a replica Deluxe Reverb PT for both higher voltage and more power. Use a Hammond 125ESE OT. Good to go!

[Allynmey]

Here's a pic from a few years ago

[Alexo]

My first scratch build was an EL34 champ. Man, did I ever make a big pile o' mistakes on that one - but they were in direct proportion to how much I learned, as usual.

FWIW, I used a 125DSE; that OT runs really hot with the EL34, if I had it to do again, I'd probably use an ESE.

[paulster]

The Beast is a great amp. It's amazing seeing people's reactions to this little thing when you wind it up!