EL-34 in a 50/50?

[venaleschatology]

Im wondering if theres any tinkering i can do to un fix the bias on my 50/50 so i can load it with el-34's. Still cooler (but i think totally impossible) would be if i could set the bias for each channel have one with el-34 and one with 6l6 (i dont use them for stereo so much as i just have them going to two stacked 2x12 and eq the two channels differently. I like the way they blend).

Like i said, not sure about the second one, but any help would be great.

 

[Blueracer]

There are several things to consider for this to work. First the filament current of a EL34 is higher than a 6L6. The specs I found had the filament current for the EL34 at 1.5A and 0.9A for the 6L6. You would need to multiply by four so the EL34s would draw about 2.4A more. You would need to check the transformer specs to see if this is within its rating. Next do the EL34s physically fit in the 50/50. I wondered about this when I was considering buying a 50/50. It seems like the tubes could hang out the back. It is worth checking before going too much futher with something like this. The output transformer would also be a possible issue. What sort of impedance transfer is it providing, what sort of power can it handle, etc.

The actual biasing is not too bad. It would mean changing a resistor in the bias supply or even better in my opinion would be to add a bias pot to really bring it in. Also constructing another voltage divider to split the operation of the A verses the B channels should not be difficult. A good tech should be able to do this. Hope this helps.

Gary

 

[Paul Secondino]

The 50/50 isn't a good poweramp for El34's mainly for the reasons that Blue Racer mentioned. The El34's are looking to feed more electrical current through them. And this isn't the same thing as setting negative bias voltage

Running El34 shouldn't hurt the amp at all but it wont sound great. I do believe that the 50/50 is capable of running 6550 though. That might be a sound you'd like.

 

[venaleschatology]

Hmm im not sure i wanna spend to much money so im i dont think i'll be taking it to any guitar techs. I do like the idea of running kt-88s though. Thanks kids.

 

[PC Biz]

Having at least two options would be cool, so I guess that's why the new power amps have EL34 capability. It might be easier to just get a new power amp. I know Guitar Center was blowing out the 2:100 for $500 a couple of years ago. Maybe they'll have something this year for the sale next Monday.

I also know that Randall makes a power amp that does exactly what you're describing. You can run one side with KT88s and the other with 6L6s, EL34s or whatever youd' like. The reviews for it are pretty good, too.