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


Hi,

I am looking to buy a used FPB-600 or FPB-700cx amp. I am wondering if I should stick with the FPB-600 because I will be using RCA inputs. I know there are adapters to convert to XLR, but is that a good idea? Isn't there an impedance mismatch or signal level issue? If that is the case, I would not be able to get the FPB-700cx to unleash it's full potential? One thing I will not do is buy a preamp with balanced or CAST outputs. Thanks for any knowledge on this!
hi_power
the 600c has xlr, cast and balanced. thought the 600 had xlr and rca but was the older chasis style and no cast.
i meant the 600 has xlr, rca and cast...
lets try this all over. i was talking to my wife on the phone and eating a bowl of soup when i typed my response...

what i was trying to say was the fpb600c has xlr, rca and cast. i thought the fpb600 had xlr and rca, just no cast and it was the older style.

i use an fpb600c now although i just listed it for sale. i absolutely love the fpb sound and actually prefer it to the outrageously expensive evo's...
Thanks Richard. I just am not sure if I should go from RCA to XLR on the 700cx. That is my dilemma. I would also like to see a picture of the 700cx guts. I can't find it on the web. The inside of the 600 is impressive.
One thing I will not do is buy a preamp with balanced or CAST outputs.

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.
[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.
Usually the capacitors. But other things can happen. Capacitor age and eventually fail.

Good listening,
Mike