Hey Mr Rayhall, I own a CAT MK-3, and i'm happy to report that i have tried quiet a few 6922 tubes... the Amperex sound really good, i must say , but after some 5 or 6 pairs tried, i couldn't use not one of em'because of microphonics or spitting.. The Philips sound very good with low noise, very low microphonics, clear good choice. I have had Siemens, Telefunky's Mullard's and a couple of others, but ALMOST all were [too] microphonic, and/or noisy. although good sounding ! [N.O.S all] So, i refer to my CAT as "the tube tester" you will want to agree with that.. The new SOVTEK's with black print are no good i agree, they don't sound good, and they will break down soon. But what's surprising here.. I got hold on some older stock SOVTEK's from the early seventies...Boy, are they good. NOT as good sounding as the AMPEREX, but very low noise, NO microphonics, and a very detailed although a bit forward sound, just on the bright side..you can cope with that by replacing the ECC 83's for MULLARD's... it's a goood combo, try it' As i live in Holland,the country of origin for these tubes, I can tell you that even here it is hard to find NOS Amperex,Siemens, [Philips is not so hard to find], So be happy if you happen to have a pristine sounding and quiet pair in your CAT workin'!! Recommend the Philips and NOS Sovteks though. E-mails from fellow CAT owners welcome on this subject... Enjoy the music, Ron.