Thursday, January 1, 2009

Fender Champion 600 Tube Upgrade



I don't think of myself as a huge tube snob but the stock 6V6 tube in this Champion 600 was really pretty bad. It was inarticulate and mushy both overdriven and clean. I installed a JJ Tesla 6V6. If you put in new 6V6, play for a while and then put the stock one back. You'll chuck it right in the trash without hesitation.


The stock 12ax7 was nothing to write home about either. The amp will improve with an upgraded 12AX7. I've swapped in a 12DW7/ECC832 for more headroom.



I liked the effect of the 12DW7 / ECC832 so I modded the circuit to properly bias the tube.


16 comments:

strato94 said...

Hi,
sorry for my bad english, I'm french...
it's difficult to translate everything on your blog. So, I would like to know if it's necessary to bias the power tube 6V6 ?
thx a lot for your answer

akavalve said...

You can just plug the new tube in. Don't worry about the bias.
The 6V6 has a "cathode bias" or "self bias" circuit so there is no need to set the bias for a new tube.

strato94 said...

thank's a lot akavalve !
and thx for your blog (I'm trying to understand all your mods)
Great blog !

Darren said...

hi there -

was wondering how this has worked out for you.

i have one of these little babies and i like it... but it's my second one. the tube blew almost immediately upon buying the thing. fender replaced the whole amp and now the tube's gone again.

the guy at the service center said he's seen a number of these come through.

not sure if upgrading the tubes will help this or if it's just a bad design...

thanks for any info!

Jesús Omar said...

hi man, i did change the 12ax7, but for my surprise... stock tube is a Sovtek made in russia.

now it has a new sovtek, same model

and i have a problem, when i try to remove the board, i try to pull and i can't do it

and sorry for my bad english, i'm mexican

akavalve said...

It should come off pretty easily.
Did you get all the screws out first?
Even the ones on the tube socket?

There's a little video here:

http://akavalve.blogspot.com/2009/02/fender-champion-600-akavalve-mods.html

Keep an eye on the screwdriver - you might see that you missed a screw somewhere.

Jesús Omar said...

i get all screws, are 4, one per side and two back, then i try to pull off and it come a little, then stop

akavalve said...

Sounds like you are removing the chassis from the amp, not the board from the chassis.

Make sure the speaker is unplugged and the power cord is not attached to the cabinet.

Sometimes the chassis is a bit tight in there and it just takes a but more wiggling to loosen it up.

akavalve said...

Sounds like you are removing the chassis from the amp, not the board from the chassis.

Make sure the speaker is unplugged and the power cord is not attached to the cabinet.

Sometimes the chassis is a bit tight in there and it just takes a but more wiggling to loosen it up.

Jesús Omar said...

right

thanks man

Anonymous said...

Hey man
really like the site and mods
just a quick question
is it possible to just swap the 6v6 for a 6l6 without damaging the amp??
and what exactly am i damaging
and if so what should i mod to compensate for the 6l6?

thanks
i really appreciate it

akavalve said...

I think the output transformer could probably take it. The big thing is a 6L6 draws more heater current and there's a good chance that the power transformer can't handle it.

If your heater voltage doesn't get dragged down when you put in a 6L6 you may be OK. You could put in an auxiliary heater transformer to be sure.

Ideally you'd probably change the cathode resistor too to bias for the 6L6.

I'll give it a shot with mine when I have a chance and let you know what I find.

Best, Andy

Anonymous said...

thanks so much for the reply andy
changing the cathode resistor sounds ideal for me
i just dont have the knowledge of what minor tweak id need for the champ to handle the bigger tube

tell me how it goes

thanks a ton!!
i appreciate it

ray said...

Hi,
Read about 6L6 plugged in on champion 600 without any mod to amp. I hv been doing that with my old golden dragon 6L6 over 2 years and recently changed it to EV5881. Whats your take on this with rgds to output transformer? Noted my amp has to be cranked to around 10 to have same volume as previous 7 or 8. Has my OT started to fade?

Tk/Raymond

TaintedElvis said...

This is a great post, akavalve. Thanks for sharing the knowledge. I am going to post it on my blues blog, just to give it more exposure and to help my readers, too. Great stuff!

Plong said...

Hi, tell me if i'm right, we just need to replace the 2 tubes and nothing else to do ?

Thx in advance.

Pat