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Can you you run EL84 and 6BQ5 together

juptonstone

juptonstone

Member at Large...
My amp runs a quad of either or EL84/6BQ5 but one of my EL84s went yesterday and I dont have a spare. I do have 3 - 6BQ5 though. Since the two are so similar, can they be run together at least for a few days, or will this throw the amp off?
 
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? these are the same tubes, just different names (EL84 European designation; 6BQ5 USA)
There are some steps to review when replacing a power tube. What amp do you have? does the amp allow for manual bias adjust?
 
you want to use the one that tests "closest" to the other one on the channel. And yes bias adjust.

But more important, what caused the other tube to go out??
 
ggregg said:
you want to use the one that tests "closest" to the other one on the channel. And yes bias adjust.

But more important, what caused the other tube to go out??
Click to expand...

I got a preamp that ended up being toast and I decided to try some repairs. The repairs worked great for about 5 minutes... after that the preamp dumped again and one of the tubes started glowing brilliant orange.

I shut the amp down and the preamp down immediately. I pulled the amp out and checked for burned or visibly damaged components and put the amp back in the system. Then I reinstalled the original pre... switched the bad tube to a new location and fired the amp up.

At that point, everything sounded fine but after about a minute, the plates in the damaged tube started to glow ever so slightly. So I shut the amp down and wrote this post.
 
I'd just wait till I could get a replacement set that are properly matched.

Look at it this way ... you'll appreciate it much more if you have to wait!

AN Ti ci Pa shunnnnnn!!!

(while you're at it, get two sets, including a pair of "sacrificial" cheapies that you wouldn't mind losing if there's issues with the amp itself.)

* I'd check here ... just picked up a TASTY little matched pair of NOS Sylvies for a very reasonable price ...

http://www.audiotubes.com/6bq5.htm

And worth repeating, although tubes DO just blow every now and then, DO at least clean and retension the sockets and check for crispy or loose wiring!
 
Given that it is cathode based it needs no bias adjustment, so I guess the real question here is... would it be best to put one 6BQ5 on each side, or would it not make any sonic difference?

And this is a temporary measure until I can get new EL84s in, or simply stick with 6BQ 5s as I havent noticed any sonic differences just using eastern european tubes.
 
>> would it be best to put one 6BQ5 on each side?
Might be better for sonics to mix them up per channel. Relative tube strength may make a bigger difference. Should not hurt either way in short term. I like the idea of a matched quad.
 
matching the idle currents is more important than matching brands. You can run 4 completely different tubes that match up electrically and the amp won't care at all.
 
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