If you are running balanced lines, its a good idea to find out if the preamp you have in mind supports the balanced line standard, also known as AES48. The reason for this is simple: in any high end system a lot of attention is paid to interconnect cables.
There is on-going conversation in high end audio as to whether or not balanced lines sound better; the only reason this happens is because not all balanced products support the standard. In a nutshell, here it is:* pin 1 is ground, pins 2 and 3 are signal, pin 2 being non-inverted and pin 3 its opposite
* the signal exists only as pin 2 with respect to pin 3; ground is not used for signal in any way- it is merely for shielding.
* the connection is fairly low impedance, if nothing else than at least at the output of the preamp
Most products get the first bit right but not the last two. All aspects have to be observed for the simple reason that if they are, the interconnect cables will cease to influence the system sound- which means they don't have to be expensive and you can run them a long ways (although the benefit is there even if the cables are quite short).
IMO/IME the cost of the interconnect cables are sort of the hidden cost of any preamplifier since you have to hook it up to get tunes :) The balanced line system is a way of reducing or eliminating the otherwise audible effects of the cable.
Here is a simple test as to whether a preamp's output supports the standard. If it is possible to connect between one of the signal pins and ground and get a sound with no buzz or hum, then it does **not** support the standard. As I mentioned earlier, the signal occurs between pins 2 and 3 and ground is not used at all other than shielding. So if the circuit is complete (no hum or buzz) by using only one signal pin and ground, then the standard isn't being supported and you will have to be careful about what interconnect cable you use to get it to sound right. IMO this defeats the purpose of using balanced lines.
