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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
10 responses Add your response
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.
oldhvymec
5,101 posts
 
Yup put the stockers back in and order up some new ones.. Why are you mixing? You have the originals you pulled? You broke an index off or something? LOL been a mechanic to long, reading between lines..
Use it anyways, won’t hurt a thing..

I don’t care what any manufacture says, match the valves and use the same kind. Power Valves and signal, you can mix the brands with different functions.. but don't mismatch left to right, just a real bad practice. You want to settle for "it will work" or "it sound good". I’ve heard how you can just throw a valve in, it will auto bias and you’re good. BULL. I’ve read their pitch. The exact reason I don’t care for them..

SQ and valves are because they ARE matched, not close enough.

They use to say the same thing on Macs, the reason most folks say "I don’t know what you hear in a Mcintosh"? Match and select good valves, then you get to hear the Wonders of Mac.. Their older valve amps are magical. Just takes a Mac junky to keep them running GREAT. They run forever. BUT to sound GREAT.. "Will work", just won’t do...

Enjoy OP...

Regards
jjss49's avatar
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jjss49
6,612 posts
 
I would install the stock quad  and order a new quad and keep the others as back ups


good advice from tuberist
tablejockey
3,892 posts
 
  "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-
I am referring to the front row small preamp tubes. The PL website mentions the 2 innermost are the gain tubes, which have the most impact, if you want to tinker with SQ. It's not night/day difference, but another way to custom tune to your liking.

The mixed power tube thing seems like a temporary way to hear your setup until you get proper replacements. 
tuberist
951 posts
 
I would install the stock quad  and order a new quad and keep the others as back ups
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?
tablejockey
3,892 posts
 
I have a PL DLHP

You could mix and match power tubes,but you're not going to hear optimum performance of any particular model. 

One of those you can...buy why? The PL units do not require matched power tubes.
jjss49's avatar
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jjss49
6,612 posts
 
good luck lg1

kt77's very close to el34's in response and need for bias, sonic character just a teeny bit different

would be more of a problem if you tried to mix el34's with say kt88 kt90 etc etc which are much more powerful with very different response
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!
jjss49's avatar
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jjss49
6,612 posts
 
primaluna's materials talk about this - you should read them

you can do it but it is not advised if good sound quality is the objective
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