2. amps-preamps
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Using Different Power Tube Types Simultaneously (PrimaLuna)

Always needing a quick answer on Sundays when the shops are closed..Murphy’s Law, Lol...

Just wanted to triple-check before I make a severe-consequences-mistake here :  Is it okay to mix one, brand A EL-34 in with three, brand B KT 77s in a PrimaLuna Prologue Classic integrated amp which normally uses a matched quad of power tubes?  I’m pretty sure I’ve been dealing with one, possibly two GL KT 77s that have been intermittently problematic for about 2 weeks but which have now gone bad to the point that re-seating doesn’t help and amp gives the red light consistently.  I don’t have a backup quad of KT 77s and need to trace down the bad tube(s).  I have the original EL 34s that came with the amp and they were working fine when I switched to the KT 77s last Spring.

if this is safe to do, is it also safe to play the amp with this mixture of tube types until I can get a replacement KT 77(s) delivered?

Apologies if this is 1 + 1 = 2 level basics...This is my first tube amp and my best Google search terms are turning up nothing but tons and tons of guitar amp articles that may or may not be applicable to my situation.  Thanks in advance.
lg1

Showing 3 responses by lg1

lg1 OP
199 posts
 
“...One of those you can...buy(t?) why?......”

Thanks, tablejockey.......I think I’ve verified that the #3 (going left to right from the front of the amp) KT 77 was the culprit and I’ve replaced it with a stock, PL EL 34.  Are you saying I might get a better temporary balance with the two middle power tube positions running the EL 34s and the ‘77s’ on each end?
lg1 OP
199 posts
 
Thanks, jjss49.  It does seem like this was in a PL ad at some point but, at my age and distant-but-intense history with mind-altering chemicals, I have to question if I saw it or dreamt it.  Good info which I’ll now write in felt-tipped-marker on my spare box of tubes!
lg1 OP
199 posts
 
Thanks, all!

Original, PL EL 34 quad is back up and running.  After living with the KT 77s for 10 months.....well, yeah,...I do like the ‘77s better but there are aspects of these EL 34s that are tough to beat.  Going to try a quad of the Mullard reissue EL 34s next and see if the hundred-bucks-less factor evens things out relative to the GL KT 77s but will definitely be revisiting the ‘77s at some future point, the fates willing.
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