#1
i want to change my stock engl 6l6gc's to some jj 6l6gc's.
now i know i have to re bias the amp for the new tubes
but i was wondering that if i like the sound the jj's would
i have to re bias the amp everytime i replaced the jj 6l6gc's?

thanks.
#3
You may or may not. You should at the very least check the bias before and after. If you don't want to have to rebias every time you change tubes within a single brand you can order more than you need. For example: you only need a matched pair, but you buy a matched octet so you get through four tube changes without a rebias.

Also, I suppose I should ask why you want to change your tubes in the first place. Are the current tubes microphonic, noisy, old and lifeless, or otherwise in an unacceptable condition, or are you just looking for a tone change? Whilst changing brands can provide a minor tonal change, a 6l6GC will still be a 6l6GC. Changing to a tube tested for early or late breakup is also a subtle change only heard at high volume settings. If there's something you particularly dislike about the tone of the amp you'd be better off tweaking preamp tubes or, better yet, modding the circuit and/or changing speakers, any of which would have a much larger effect on the tonality of the amplifier and cabinet combo. If there's something legitimately wrong with your power tubes, though, you should replace them.

The first thing I'd do is actually just check the bias on them. If they're biased too hot or too cold and you rebias them to a spec more suited to your style (and within safe operating parameters) then you'd notice more change than from any of the above besides a circuit or speaker change.
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#4
My amp sounds awesome tube are still great I was just curious about buying new tubes. I am not sure why I did not think of buying a quad set for 2 spares. When my tubs die I was thinking of switching to jj's I hear they will open the amp up more and that engl rebrands cheap Russian tubes. I read engl amps are a bitch to bias I have yet to need to but I figure the less I have to rip apart my head the better. Thanks for the imformative post.
#5
No prob. I forgot to mention that many people think you should also replace the phase inverter tube every time you change power tubes if they're being replaced due to wear, as that tube also takes a hefty beating. I haven't experimented with that, but you may want to consider it.
My Tele Project!

Cheapy Johnson Steel String Acoustic
Les Paul Ripoff w/ SD SH2 and SH4
Modded Crate V18 2x12 w/ Weber Speakers
Squier Deluxe 5-string Active J-Bass
Acoustic B100 15" Bass Combo Amp
Gray VS Jekyll & Hyde
Vox V847A Wah