Guitar Gear Forum

I'm considering rebiasing one of my amps from E34L power tubes to 6L6 tubes, but I've never done it before, so I don't really know how much it will cost and what it will/won't do for my tone.
Any advice will be appreciated.

It's not too complicated, but if you've never done it before I'd suggest having a tech do it. Check out youtube, there's tons of vids of people showing how to bias an amp.

Whatever you do - please remember that there are high voltages in there that can kill you even if it's unplugged.

Placemat Jackson wrote:It's not too complicated, but if you've never done it before I'd suggest having a tech do it. Check out youtube, there's tons of vids of people showing how to bias an amp.

Oblivion DC wrote:Whatever you do - please remember that there are high voltages in there that can kill you even if it's unplugged.

Thanks, got it.

doesn't that swap usually require a resistor change in the circuit?

What electronic equipment is needed? I have a multi-meter....anything else?

I'm assuming you're sure your amp can take either of those tubes. If not it'll take a lot more than just a rebias. Other than that it can be done with Multimeter/bias probe. Do plenty of reading and you know to what voltage you'll be biasing to.

Finally ONLY ATTEMPT IF YOU FEEL CONFORTABLE FIDDLING ON THE INSIDE OF YOUR AMP!!! READ PLENTY AND WATCH VIDEOS!! The info is there for you to do it but you must be able to implement the info correctly and safely.

mamberg wrote:doesn't that swap usually require a resistor change in the circuit?

Fixed bias or cathode bias require a resistor swap to change bias. With adjustable bias obviously there's a potentiometer to sweep with.

El34>6l6 is the easier direction. The 34s use higher heater current and use pins that are unused on a 6l6. You would have to account for those differences if you were taking a 6l6 amp the other way.

Goslats wrote:What electronic equipment is needed? I have a multi-meter....anything else?

I normally roll with a dmm, test leads, and resistors on hand.

As these guys have said, if you don't know where the high voltages are stored and understand how to easily and safely discarge the components then you really have no business openning a chassis. Safe work environments are important as well.

zach told me that most of the time a transformer swap is necessary (which is the case with JCA's)

My understanding is you can go from EL34 to 6L6 with only a re-bias IF there is sufficient range of adjustment on the bias pot.

You can't go from 6L6 to EL34 without siginificant modifications to the amp.

Disclaimer. I build amps, but I didn't build your amp so ask your tech before proceeding or have him do it.