Can I use JJ EL34s in my Dyne?

I have a quad of JJ EL34s that were in my Marshall a while back. They have '48' written on the base, which I presume is some sort of rating. Is this an indication of whether they fall within the safe bias range of the Electra Dyne in EL34 mode?

Hey,
EL34 is the requirement, because of the voltage they draw, which is different from 6L6. After that, you're on your own. Whether you hear a difference depends on your ears and the tube quality. Just make sure you're on the right voltage setting (back of the amp) or you will damage something.
Doesn't have to be mesa tubes by any means, although mesa sure wants you to buy their tubes. Make sure you buy matched tubes, that balances the power load between the tubes optimally.
Can't wait to put my ED through its paces, I am wating for a mains transformer, since I bought a used US model here in germany and I don't want to use the stupid stepdown transformer the guy gave me...
good luck and happy trails.

Since Mesa's do not have an adjustable bias, the el34's must be within the proper range for the amp to prevent damage. The "48" is ambiguous as while it likely means idle current draw for those specific tubes, it does not tell you how that value was determined.
Was it on a tube tester or an amp? Also what amp? Even if by some chance tested on a Mesa, 48ma idle sounds a bit on the high side.

Then again, it depends on the plate voltage present at the 48 value. Volts times amperes determines power and ultimately, power dissipation of the tube, meaning with lower plate voltage you can run a higher idle current.

But really, both values should be measured by a tech to determine if safe for your Mesa. Also know that if a non-Mesa output tube fails and damages the amp, your warranty may not be honored (if not expired at this point).

You risk damaging a nice amp if you just install them and start using them.

Good luck!

RandomGecko said:

I have a quad of JJ EL34s that were in my Marshall a while back. They have '48' written on the base, which I presume is some sort of rating. Is this an indication of whether they fall within the safe bias range of the Electra Dyne in EL34 mode?

Click to expand...

If it were me, I'd get a new matched set from a reputable dealer who clearly understood Mesa bias tolerances. Not worth the risk to the amp or it's perfromance