Tubes for VTA ST-120

Hello, Awhile back I built a ST-120. I have been very happy with it, but I think it is getting time to replace the power tubes. Or at least buy a spare set. I have been using Sovtek 6550's from Jim McShane; for various reasons, Jim is no longer restocking tubes. Does anyone have a good source for matched quads of 6550 , KT-88 , or other tubes that will fit a ST-120? I am more concerned with price and long life than I am with fine nuances in sound.

match quad Sovtek 6550 $250 plus $10 shipping
match quad JJ KT88 $320 plus $10 shipping

check out vacuumtubevalues.com Good source for matched quads. Good pricing too

Not sure if you’ve done anything yet, but, after rolling quite a few variants the TAD KT88-STR matched quad is my absolute fave.

Rest of the system can be seen here for context.

https://cgi.audioasylum.com/systems/10769.html

You don't REQUIRE a matched quad. TWO sets of fairly close pairs will be fine if you can't get a quad.

Antique Electronic Supply has Apex matched tubes. Apex matching is much more precise than a single point match. There is no price difference between 2x pairs and a quad.
If you order pairs, call or add a note to your order for the pairs to be as close as possible

Antique Electronic Supply 6550

Apex Tube Matching

I have no association with AES or Apex

I ordered a matched quad of Apex matched J&J 6550s from Antique Electronic Supply when one of my kit supplied Sovteks failed.  Noted a significant improvement in the bass response.  This was something I had not expected, but has caused me to stop experimenting with solid state replacement amps and subwoofer supplements.  I am convinced the VTA ST 120 is the best amp for my taste.

Better bass could be that you now use matched tubes which made the output transformer do it's job.
Unmatched tubes will magnitize the transformer reducing it's ability to transmit bass.

Interesting… I have no idea what the Sovteks spec’s at, but the difference with the J&J set was remarkable.

Mismatched tubes may also drastically increase distortion, depending on the mismatch delta.

I grabbed a quad of psvane for my 120.  6 mo. So far great. https://www.vivatubes.com/new-matched-quad-4-psvane-kt88c-hifi-vacuum-tubes/?gad=1&gclid=CjwKCAjwzo2mBhAUEiwAf7wjkgvxFnIgX3q53IpUf6RLICqiWUzn3vS4dleo3zJDXitcQaUtm4iblRoCIDAQAvD_BwE

I have had my Psvane KT88C's for about 1 year now. They sound great! much better than any of the 6550's I have tried.

smoorenc wrote:I have had my Psvane KT88C's for about 1 year now. They sound great! much better than any of the 6550's I have tried.

So nice