No Balanced Circuitry

It means the the input/outputs are balanced but that the circuit topology is not fully differential, which would indicate a positive and negative gain stage for each channel. Twice the circuitry which is why most manufacturers don't do it.

Hi Spin,

So does it mean that there is no sound significant sound different?

Twice the circuitry which is why most manufacturers don't do it.

This statement is incorrect. It does not take twice as much circuitry to go differential!

Clarrie, the answer to your question is probably yes. If the circuit is not internally balanced, the chances are very good that the connectors are just there for convenience.

Does it mean that the XLR output are not fully balanced....???

"Fully balanced" is a term that applies to amplifier construction and not the input or output.

Input can be balanced (in non fully balanced amp) by either Transformer or Instrumentation Amplifier. To make output balanced requires additional inverting stage (gain -1). XLR cables are less susceptible to noise, have locks and hidden (female) input pins. Other than greater noise immunity balanced cables should be less transparent than RCA cables because of this additional input and output stage.