Krell FPB-600 or FPB-700cx - RCA vs. XLR Input

[Clearly the 700cx is not for you; in order to obtain all the benefits of this amp you would need to do just that, especially CAST, otherwise you are wasting your money.]

Stevecham - That's what I was wondering. If the preamp signals aren't matched properly, you can lose an awful lot from the amp. I wouldn't want to spend that much and have THAT happen.

The Krell 600, 600c or 700cx can be used successfully with a RCA output preamplifer - some people even prefer this mode to the XLR or CAST mode. Input impedance of MCX models is 100 kohms that can match almost all known preamplifiers.
Tube preamplifiers known for having DC offset or DC leakage should be used with the internal coupling capacitors engaged.
"A one piece RCA-to-XLR adapter is available
from Krell Industries, to allow single-ended operation
using the balanced XLR inputs" - taken from the Krell MCX manual.

Microstrip,

I was also talking with Larry at High End Palace and he thought using the RCA to XLR cables would not be so bad. That's good. It leaves me with more options.

Owned many Krell amps including the 600. Use balanced connections for the best sound. Do not use coupling cap's unless you wish to destroy the sound...only very tweaky single ended tube preamps would be a problem anyway. The KCT is the best match or ARC if tubes are your thing. The FPB 600 was/is a great amp and sounds way better than the Evolution crap I owned and sold!

I own a fpb-600 for years now . What goes bad in a amp like this.