Re-tubing a McIntosh power amp

GL KT88s are about 210-230.00 per quad. I'd stick with KT88s not 6550, and yes there is BIG difference.

GL are a good sounding valve for one. A 6550 in the older 1961-67 275s that's a different story. The amp is made differently. Actually I like a GE6550 better than even the old GLs. BOTH are wonderful valves though..

PSVANE is just a no no too. I tried a few times.. The signal valves not too bad, but the power valves.. YIKES!

I know I have used some Solvex that were REALLY good. The problem I had was the failure rate out of the box and for about the first 50 hours or so.. SUPER high.. I bought in bulk, and didn't lose my shirt, BUT I was burning in quads for a while.. 15% failure rate, THEN they were fine..

Over 30 valves out of 200, three different times.. Some put on quite the fireworks display in a tube.. Scare the heck out of you the first few times.. :-)

OP rolling valves is swapping, but normally we roll small valves for the final tweak. Some have fewer to roll than others.. That's all.  LOL

Golden Lyon KT88s. 4-6000 hours

12AX7, 12AZ7, very close. Golden Lyons, Tellies, RCAs (if you can afford and find them) or if you want a sharper edgy valve, PSVANE
all over 5000 up to 7-8000 hours.

They last a LONG time in a new Mac for sure. I have a GG with 15000 hours, I did lose an original power valve within the first 1000 hours.. It was a made in China valve. It said Mcintosh on the side.. LOL it was probably a JJ.
I have Solvex in there now, wonderful valve for the money.

I paid about 75-80 per quad in bulk. 15% failure, no kidding out of the box or within 50 hours.. After they were burned in (and didn't BLOW up).. Just like any other valve.. 5-10000 hours

A quad of Solvex is 125-175.00 close

Regards

There is no crap shoot with GL KT88s or anything tested and burnt in..

I know of two vendors that recommend JJs, because THEY don't have failures.. ANY valve that is tested and then burnt in, very seldom does fail.

But recommend them because they don't FAIL. I'll pass, they are a so so valve at best as far a SQ. Just about anything sounds as good and many many other valves sound a LOT better.. I'd take a Valve Art over JJs..

I have piles of the little critters here.. ALL questionable as far as SQ but they test just fine. Tap the glass with a pencil, LOL everything changes.. Underwater they go.. or echo chamber effects..

I use a lot of mill spec surplus from Russia. 1/3 are bad BUT after testing and burn in, better than ANY JJ I've ever used. 1.25 each in bulk..

Golden Lyon OP you'll be very happy.. so we are clear, I'm not huge GL fan, I  just happen to know Macs and what they like pretty well after 50 years of fixing and using them....

I'm listening to a MC225 and a C20 right now..  Looking at them, you would swear they were brand new out of the box Macs.. 60 + years old now.. ALL factory VALVES, I've never changed a single one in that pair..
Caps and resistors YES.. That's it..

Heaven will have that pair of Macs in it.. :-)

Regards