Do I really need to match a quartet of tubes if only one has broken?

FreddieVanHalen

So, one of the EL34 valves in my 100W head has cracked. I suspect it was partly due to the courier when the amp was delivered a few months ago as the amp hasn't had a huge amount of use. Anyhoo...

As the other three tubes must have loads of life still left in them, do I really need to replace the ruddy things as a quartet or can I jam any old tube in there? There are some numbers written on the cracked EL34 which say 27.2 and 4.81.

I have no idea what they mean, if they mean anything at all....

All help appreciated!

ICBM

You can use any valve which is reasonably closely matched, but unfortunately the tester numbers don't mean much unless you get another one from the same vendor, since they depend on the test conditions.

*Best* practice is to buy a new matched quad and keep the three good ones as spares. You always need spares.

FreddieVanHalen

Thank you @ICBM, even if that was the answer I was not hoping for :-)

New tubes here I come!

robinbowes

Sell two as a matched pair, and keep one as spare.

R.

FreddieVanHalen

robinbowes said:

Sell two as a matched pair, and keep one as spare.

R.

Haha, not a bad idea actually!

ICBM

Not really, because a pair of spare valves is more use than a single one.