Bugera 6262 use & bias of only 2x6L6

[petlus]

I want to use my Bugera 6262 (which has stock 4x6L6 power tubes) with only 2x6L6... this should be possible I guess.

I.e. for swapping to EL34 there is implemented the possibility of changing and measuring the bias from outside the amp so I think it shouldn't be a problem to do that also for only 2x6L6.

Does anyone know which 2 of the 4 powertubes I have to pull out and what bias should be applicated for only 2x6L6 left?

Probably I need to change the speaker impedance switch... or am I wrong?

Thank you for any advice

Ron

[gribnick]

Although I can't say with any certainty without having seen one, usually the push-pull pairs are the inner tubes and the outer tubes. So pull one of the pairs (two interior OR the two outer tubes) and you'd have it .. unless Bugera did something funny (always a possibility). Try it and see how it sounds. That should give you a clue..

And yes, if you want to keep the impedance matched, switch the speaker impedance to the next lowest (16 ohm speaker into 8 ohm, 8 ohm speaker into 4ohm) if available. Otherwise, running a 50% mismatch isn't horrible. Just may change the tone a bit.

Just be aware that this is NOT a drastic volume change. You can notice it but not by a lot (we're talking 10-15% or so perceivable volume change at most).

On thing I was cautioned about is that if your amp normally runs with, say, a 5 amp fuse (which is what my 6505+ has), when running with two tubes (which lessens the draw of course), the extra time it will take the 5amp fuse to blow could damage something so the recommendation I got was run a 3 amp fuse in that case instead..

Switching in some EL34s for any of the tubes has its own potential issues. It's not just a bias issue (although that is certainly part of it). There are impedance issues (your OT is optimized for 6L6 and will do less well with EL34s) plus the heater current for EL34s is nearly twice the 6L6s so you can run into serious supply issues and fry something if the amp was borderline to begin with.

If you are talking about mixing tubes, that's a different ballgame with additional issues of balance. Not saying impossible, just improbable to work well by popping some tubes in it and hoping. And for sure kiss your warrantee byebye.

Lastly, on switching to EL34s, there is a very good reason why most of these hi-gain amps come with 6L6s. Because they DON'T break up at the drop of a hat like the EL34s do which in a hi-gain amp can very quickly and easily turn to mud that most people don't like. YMMV..