6550 tubes

350b,
When I was primarily using my push pull amplifier (6550/KT88) failing tubes were a problem with various brands. I had the most sucess by far with the SED Winged C 6550. In contrast, my SET amplifier uses the 300b tubes which are 100% reliable(so far after 4 1/2 years) and are true work horses in comparison( and sound much better).
Charles,

Agree 100% with Jea48, especially re Upscale Audio. I've heard that the Russian factory that made Svetlana Winged "C" tubes burned down, but Audio Research has a supply on hand.

As Jea48 just said, Upscale Audio burns tubes in for 72 hours and does a very good job of matching, which is very important in push/pull type amps.

Don't know the amp you are using but check out Tung Sol KT-120s. ARC dropped in KT-120s as a replacement for 6550 Winged C tubes several years ago. But be careful. Not all amps can handle the extra power draw demanded by the KT-120s.

Regards,

Bruce

If you can find them NOS GE solid grey plate 6550 tubes are my favorite 6550 type power tube. Another favorite also are NOS Sylvania 6550 tubes. I've used these tubes in a Jolida JD-502P amp at various times.

If you are going to go for KT-88 type power tubes my favorites are JJ Blue Glass KT88s and the Penta Labs solid plate KT88s. I believe Doug's Tubes on Long Island has the Penta Labs in stock.

My personal favorite is the original Tung Sol 6550 black plate followed by the grey plate. Another nice tube that is tough as nails is the Ei KT90 type2. The SED 6550 is a very linear sounding tube and if you like that tube the KT120 may be for you also.