Balanced vs. Unbalanced - What does it mean?

Cam -- No, I think that Shadorne was speaking in more general terms, and the issue he cited about overdriving consumer-oriented gear with pro-oriented signals is not applicable to your situation.

It would be a concern if the outputs of a pro-oriented source component, or a pro-oriented equalizer or processor, were fed into the line-level inputs or tape inputs of a consumer-oriented preamplifier.

In your case, though, you are dealing with a preamp-to-power amp interface (meaning higher full-scale voltage than consumer source component line-level), and with both components being consumer-oriented. Your power amp has an input sensitivity of 2 volts in unbalanced mode, or 4 volts in balanced mode. That will certainly not result in clipping or overdriving when being fed by typical components.

In fact, the opposite will occur to a minor degree if you go with the adapter cable approach -- you will have to turn the volume control up by 6db relative to where you set it when using the power amp's unbalanced inputs. That is because instead of feeding the amp with a balanced pair of signals that have equal amplitudes and opposite polarities, you will be substituting ground (0 volts) for one of those polarities, resulting in the difference between them being half as much.

The only negative effect that could conceivably have would be to increase background hiss slightly, but unless something is marginal in your system to begin with that will not be a perceptible effect. You can test that right now, in unbalanced mode, by simply turning your volume control up a little bit from where you normally set it (corresponding to a 6db increase, as best as you can estimate that), with no music playing, and seeing if the hiss level becomes objectionable.

Regards,
-- Al

True diff. balanced circuits use "common mode rejection" to reduce the noise floor of the equipment and increase signal to noise ratio. (not necesarly just line noise and RFI)

Some (many) components have XLR connections tacked on the back, but the circuits are not true diff balance designs and many times they may actually sound better just using the RCA jacks because the signal path is actually shorter.

Generally, the input inpedance is not the same for the XLR and RCA jacks, so things may sound different.

Almarg - Actully, Audio Research, at one time sold an active component just for converting from single ended to balanced (and the other way too). Did anyone ever buy one of these. (I think it was at the time of the LS5 preamp that only had XLRs and NO RCA jacks.)

It would be a concern if the outputs of a pro-oriented source component, or a pro-oriented equalizer or processor, were fed into the line-level inputs or tape inputs of a consumer-oriented preamplifier

Exactly. If you use a Benchmark DAC1 with the XLR ouput into a consumer grade preamp or poweramp then you will probably need to set the attenuator pad in the DAC1 to drop the signal level by 20db. (This is wasteful of the higher ouput capability of pro balanced lines. It is generally a good rule of thumb to use higher level signals to give you more dynamic range over the equipment noise floor. It may well be enough of a difference to be able to hear something very soft or 60 db down versus not hearing it at all...)

I'm not sure if this has already been noted here, but I'd like to clarify: You cannot be sure that an unbalanced output can be effectively run into a balanced XLR input merely by the simple addition of a physical adaptor. ARC gear will not work correctly in this set-up. That is why ARC sold their transformer.

IIRC, ARC's power amp protection circuitry will be triggered by the unbalanced input signal and severely limit the amp's power output. This is evidently a function of the protection scheme that ARC uses in its power amps. Other brands may (or may not) have similar problems. Probably best to check with the manufacturer.

Good Luck.

Marty