Krell FPB from C to CX

How big is the difference between the latter CX family and the older C modell?
Soundwise and technically!
Is there a differnce in tonal balance, darker, more open, sweeter hights aso.?
I notice weight is thesame!
Is it via the cast connection most improvement is to be won, or equally as much through xlr/balanced?

Could the upgrade be done by retailer techs or, do i have to send the amp to Krell in the US?
Also wish to know, if Krell have some kind of service center inside the EU-region?

All I can say about the CX upgrade is that I heard enough of a difference to get it! I did not upgrade I traded, but when I first hooked up the FPB-400CX I was amazed!
I have owned several Krell amps and can tell you they sound like shit out of the box and take a very long time to break in. (300 hours min) This thing was musical right out of the gate and only got better. I dont always here the differences in all those flavor of the month upgrades or tweaks but this one sold me.

From what I've heard and read, the "c" series has the old
traditional "Krell sound" which is the tendency to be very

The newer "cx" series are said to be more "musical" and
"sweeter" than the "c" series - both with CAST input and
XLR input.

I believe the upgrade can be done "in the field" by your
local retailer techs. I don't believe the amp has to go
all the way back to Krell. The local techs can replace
the needed circuit boards.

Dr. Gregory Greenman