MBL C31 C51 Interconnects?

I received an answer from MBL. Its funny that in the C51 manual they recommend RCA.

A balanced connection like XLR does have advantages over a single ended connection like RCA. Firstly, the balanced connection does carry 6dB more level because it carries the same signal twice, in phase and out of phase. A RCA connection does just cary the signal in phase vs. ground. While the signals carried on both connections are the same, the advantages of a balanced connection are, that it is much less prone to any interference signals (radio, mobile phone, etc.). For short connections this might not make much of a difference, the longer the connection though, I would always prefer the balanced connection.

Mit freundlichen Grüßen

Achim Scherner 
Customer Support Manager

thinking out loud here; If the unit's mentioned are a single ended design using balanced just adds more in the signal path, circite to convert from single ended to balanced and back. if you don't need balanced for long runs it maybe better single ended. ie RCA.