CAT owners, Ideas for best NOS for SL1 MKIII

I've used rca, telefunken, and siemens (for 6922). I ended up with siemens because I liked the sound (neutral-"ish" and preserved / enhanced the dynamics) and, mostly, because there were 4 available whose characteristics "matched".

FWIW, it wasn't a night & day difference, the stock tubes sounded good enough, anyway!

IMHO, For CAT and Audio Research, Siemens 6DJ8 probably is the best choice. It adds body and smoothness to the sound.

I have an old CAT so my experience may not be identical, but I too prefer the 60s Siemens and if unavailable, Telefunkens (but not the IMO overpriced CCAs)

S23chang's really got the tube of choice dialed right in for either the Cat pre's and ARC's sp series preamps. Siemen tubes are sonically the clear winner in every way. They better any of the other nos amperex's[bulgle boy's included here],mullards and the telies. Another decent sounding tube for the cat is the russian military nos 6n23ev's. These are "not" the same tube as the current sovtek 6dj8's or 6922's. They are smooth, have great bass weight, and are dead quiet,The best is they will last forever in the hard running cat. All the cat's have always had a penchant for shortening the tube life of the 6dj8. As a matter of fact,the siemen e188cc was my tube of choice in the cat as it will handle a higher bias voltage than the gold pin e88cc and typically give one close to 5000 hours of tube life.One should only expect about 1/2 that life from the typical nos ecc88's.