Pass Labs & Belles class-A amplifiers

My XA30.5 defintely said it was 15kohm unbalanced, maybe the monoblocks have higher impedance? I would ask Pass Labs. If it is 20kohm, slighly better yet for tube pres, but I do think you use many tube preamps even with the 15kohm rating if that is correct. I talked about this with Pass Labs before buying the XA30.5 as I knew I would be using a tube preamp, and I remember feeling comfortable that I would not have any audible problem with my preamp at the time, the Joule LA-150 MKII.

Again, the specs on the Pass Labs website to which I linked are 20K ohms unbalanced for the XA-30.5, and was corroborated by John Atkinson when he tested the amp.

The manual, see page 12

http://www.passlabs.com/pdf/product%20manuals/xa30_5-om.pdf

says 15kohm, and also my recollection in discussion with them. The XA60.5 manual says the same thing. But, either way, I still think it will work fine with most tube preamps with under 1000 ohm output impedance.

I suppose only a call to Pass Labs will answer the question, which seems ridiculous for a company known for its excellence.