10 meters of interconect cable is too long.

Yes, unfortunately you are likely to experience some degradation of sonics at that length, especially given that the interconnections to the amp are single-ended. And a simple RCA-to-XLR adapter at the outputs of the preamp will not help.

However you may want to consider connecting the outputs of the preamp to a Jensen PO-2RX transformer, via short unbalanced interconnects, and connecting the outputs of the transformer to the amps via balanced cables. That would result in the long cables being driven with a true balanced pair of signals. Although in doing so the relatively high output impedance of the preamp (measured by Stereophile as 370 ohms in the midrange and treble, but rising to a very high 6.8K at 20 Hz) could conceivably still be an issue, as the 1:1 turns ratio of the transformer will not change the impedance with which the long cables are driven. Trying it is probably the only way to be sure.

Regards,
-- Al

Thanks for advices, next project will upgrade preamp with xlr connections.
Have a nice weekend, 
KD.

The degradation in sonics is far greater than anything anyone has mentioned so far. Its nothing like what you think. The degradation that really matters is nothing to do with the length per se. It has to do with the fact that whatever you can afford to spend on the interconnect will buy you immensely more performance at 1m compared to 10.

Go ahead and do it if its so important. It better be.

Just noticed your $4500 budget. That kind of money will buy you 1m Synergistic Research Atmosphere Level 3 Euphoria with a ground block. This one interconnect will elevate your system above Kimber to a level you simply would have thought impossible. Instead you will spend that same money to achieve what can only be described as mediocre at best. Talk about degradation! 

Go ahead and do it if its so important. It better be. It really, really better be.

... next project will upgrade preamp with xlr connections.

FYI, simply adding XLR connectors to the preamp will not help, because you would still be sending single-ended signals into the cables. Unless, that is, major modifications were made to the preamp to allow it to generate true balanced signal pairs for each channel. That would likely involve addition of a tube, physically large output coupling capacitors, and other circuit elements, assuming there is room to fit all of those things.

Simply adding XLR connectors, while providing them with unbalanced signals, might result in minor sonic differences compared to running long RCA cables due to differences in the cables that are used. But those differences could just as easily be for the worse as for the better, compared to running long RCA cables.

The transformer approach I suggested is far more likely to be a good solution.

Good luck. Regards,
-- Al

A 30 foot speaker cable is much better than a 30 foot interconnect...........