Do long interconnects degrade sound?

I recently moved into a new home and I would like to use my Krell 400xi intergrated as a preamp for my main speakers in my living room (PMC OB-1). The Krell has a preamp out. Currently the Krell is powering my main speakers for my plasma in my den. In addition, my source is also in my den. Ideally, I would like to use the Krell for both applications which would mean that I would have to run extremelly long interconnects from my amp in the living room to the Krell in the den. I know XLR's would be best for long runs, but is 50+ feet too long for interconnects?
This seems to be a controversial topic.

In the good old days, longer interconnects and shorter speaker wires were considered a tweaky must for any self respecting audiophile.

Later, some people tried to convince me that it was a bad idea.

Most recently, I deferred to who suggested that runs of up to 50' should be no problem, at least for my ARC SP-11 Mk II preamp running into my Levinson 23.5 amp.

I think I, therefore, increased the length of my interconnects to as much as 40', which is working just fine.

Other people may have more technical advice here, but I have never had a problem with this configuration.
I agree with Cwlondon, your Krell should drive 50 feet of low capacitance interconnect with no problem. If you want to be sure, check the specification of the chosen interconnect (at final length) and call Krell with the data.

Most high end cables are so low capacitance that even 50 feet would effect highs (roll off) only above approximately 100 Kh. It's even less of an issue with balanced because the output impedance is generally very low (600 Ohm), making the load even easier.
Thanks guy's for the great advice! My wife wants all the electronics in our den, but I don't want to run 50+ feet of speaker cable to my OB-1's in our living room since I am sure this would degrade the signal. I am looking to purchase some small mono's and I will run long interconnects back to the Krell. Thanks again for your help.
As long as you don't compare the sound you get from using your 50+foot run to the sound you get from using 3ft runs then you should be fine. Either way you can definitely still enjoy your music. Sound, convenience, and looks are all factors to consider. Some of us sacrifice looks and convenience completely for that extra bit of sonic improvement. While others sacrifice a bit of sonic potential for better convenience and or looks.

Depending on the quality of cables you get, 50ft runs can be expensive and could be somewhat of a visual disaster if you're running the cables along the ground. It might be worth getting another preamp. Something to consider though.
Albertporter...Do you really think 600 ohms is a low output impedance? 600 was typical of tube preamps (12AU7 cathode follower) but I have heard that some modern tube units are down to 200 ohms or less. Solid state typically runs 50 ohms or less.

I belong to the "long interconnect, short speaker cable" school of thought.
I have experience with long interconnects 75+ feet.

RCA type have a tendency to pick up more hum or ambient electrical noise which is apparent when you have the volume turned up and no music playing....hiss or hum.

XLR driven by balanced amplifier cables are far superior for this problem of ambient noise because of the shielding and less grounding issues ( which can set up small current loops).

In either case it is just the hiss that will be a problem and the sound is not degraded,
I would add that the music sound is most unlikely to differ audibly between the RCA and the balanced XLR is just the background hum or hiss that may improve (from ambient electrical noise from appliances power and AC's etc.) my advice is to try RCA first and see if it works for you and your home conditions before going to XLR.

One other out if you play loud music ....having a preamp far away may lead you t oover power speakers without knowing,

Good luck!
Eldartford, probably should have said
600 ohms or less

As for the Krell, here are the specifications for its RCA outputs. No balanced outputs on this model, but who cares with that low an impedance?

Sidebar 1: Specifications

Description: Solid-state, remote-controlled, stereo integrated amplifier with 5 line-level inputs
1 balanced, 3 single-ended
1 single-ended tape loop
1 set of single-ended preamplifier outputs.
Power output: 200Wpc into 8 ohms (23dBW)
*Output impedance: 0.17 ohm*

Even inexpensive cables, such as sold by The BlueJeans Cable Company ($83.00 for 50 Ft. RCA) is only 17 picofarads of capacitance per foot.

The point is, it's what this gentleman needs to keep peace in his home. I have a pair of 60 foot BlueJeans RCA cables in my HT system and it's OK for that use.
Albert...0.17 ohms for a line level output!! Are you sure?
That sounds like the power amp.