I’m currently pleased with Phillips 7027as as power tubes and rotate signal tubes to compensate when I try different rectifiers in my DAC, currently some 60s amperex sq’s and some Mazda e188cc’s.  I really like the Mazda’s.  A little more sparkle than with the amperex, but similar.  I would like to try some of the new issue genelex kt77s and kt88s one day.  Ive tried most of the other power tubes mentioned in the forums and prefer the 7027a’s.  The new production Tung Sol versions were surprisingly good, although I felt not as good. It seems like I bought the last 10 Phillips versions (8 matched and 2 spares) on the planet so will have to find something else eventually.  

Our current ZMA system is in a small to moderate sized combined office / art / music space. I am planning a second system using larger more efficient speakers in a larger space. So far I’m very far down on the waitlist for two SE84UFO25s and a CSP325 and am figuring out then rest.

Jon,

Most ZMA owners posting on this forum have noted positive results with new production KT-66, 7581, 7027A and KT-77 power tubes. Given a 2000-2500 hour lifespan of power tubes and the high cost of NOS tubes, most of us have opted for new production tube quads as replacements in the ZMA.

Given our different system builds and more importantly listening room conditions it can be a toss up as to which will sound best, let your ears be the judge. With new production tubes costing $100-$200/matched quartet you can experiment to some degree without breaking the bank.

New Sensor produces rebranded TungSol, Gold Lion, Mullard, and Sovtek tubes and these are readily available from online sellers. I have enjoyed Gold Lion KT-66 and KT-77 tubes, along with TungSol 7581 and 7027A's. Also the Tube Amp Doctor 7027A's. Each tube has different attributes, so my suggestion is to try a couple sets for +100 hours and listen for what sounds best in your system.

HK

Jon,  I do push my 7027As harder biasing closer to 68mA.  I'm probably just wearing them out since I really don't hear a difference when biasing lower.  I'm biasing my Tung-Sol 7851As at 56mA though.  They won't bias as high as the 7027A anyway.

0C2 would not, I believe, work, quite a different tube. It's possible that 0C3, 0B3 and 0D3 might work--they do in my SE84UFO3 Monoblocks and the Torii Mk III that I used to have--but they aren't mentioned in the manual for the ZMA. I would wait until a ZMA owner responds. . . .

Jon, an 0C2 is a 7 pin small tube, the 0A3 (and 0B3,0C3,0D3) are larger 8 pin tubes. An 0C2 just won't work in the ZMA. An 0C3 would fit in the amp, but I'm not sure it will be a good choice--ZMA owners or Steve would need to weigh in--I have never owned or heard a ZMA myself. The manual does not mention any substitutions.

(Edited: thanks CA)

Ok, thanks.  Doesn’t seem worth pursuing.