Based on my use of transformers with my current gear, I will respond to a couple of Ralph's transformer comments,
If you go the transformer route as mentioned above, place the transformer as close as you can to the preamp can keep the cable to it short.
This applies if you are using output transformers. However, I had much better luck with input side transformers. Since my preamp to amp run is less than 3M, I use 2.5 to 3M single-ended IC's to two separate single channel Jensen input transformers then very short balanced IC's (less than 1M) from the transformers to my balanced Clayton M300 monoblock amps.
The transformer will have some artifact; although the Jensens are very good I find they reduce bass impact and liveliness,
The first part of this statement is true, but with the Jensens it is my experience this is inaudible, or at least unnoticable. So far, I prefer using my favorite single-ended preamp with the transformers to using the balanced preamp I have tried without transformers. In other words, I have found the sonic differences in preamps to be much greater than the sonic penalty resulting from losses that may occur when using the transformers. Some highly regarded manufacturers use transformers from companies like Jensen and Lundahl on the output side of preamps and and/or the input side of power amps. The literature provided by Jensen shows pretty much flat response throughout the audible frequency band. Source impedance (the output impedance of your preamp) must be below 2K ohms and the load impedance (input impedance of your power amp) must be above 10K ohms according to the literature, and they recommend keeping the transformer to amp cables as short as possible. I have found this to be an excellent solution to the problem of driving balanced amps using a single-ended preamp. I have not tried the transformers to drive balanced preamps from single-ended sources, although it seems that should also work if the output and input impedances are within the limits provided. One last thing, the Jensen transformers are relatively inexpensive, being just over $200 for the stereo model and around $125 for the single channel model (which comes in a slightly more robust case for pro applications). You have to ask them for the single-ended model, but it is perfect when using monoblocks that are more than a couple of feet away from each other. Check out the link to Jensen posted above by Al.
