Balanced vs. Unbalanced - What does it mean?

“Line-level” signal level for consumer audio equipment is nominally -10dBV (0.32V RMS). However, “line-level” signal level for pro-sound equipment is +4dBV (1.23V RMS). Simply put, pro audio gear is looking for a 14dB higher signal level.

Anyone who suspects that 14db additional signal level will likely translate into significant benefits in dynamic range would be correct (never mind the length of your audio cables). Most electronics does not perform as well at very low signal levels. Of course, it won't matter much for a hyper-compressed Green Day album but on a good recording you'll often notice a small or slight difference with balanced.

Also the "hum" that Al mentions is even more of a significant problem when using lower signal levels - not to metion the lack of shielding and the problematic grounding of chassis when using RCA. Serious audiophiles really should consider balanced before investing in things like resonator cups, as there is science as well as a long track record behind balanced XLR equipment.

Nevertheless be careful. Pro audio gear will often be too "hot" for consumer grade stuff and you'll get clipping unless you attenuate pro quality balanced signals when interfacing to ordinary consumer grade gear. RCA is ubiquitous ONLY because it is cheap and often adequate.

I should add to the mention of adapters and adapter cables in my previous post that although these are viable alternatives for interfacing a single-ended output to a balanced input (using an rca-male to xlr-male cable or adapter), interfacing in the other direction (balanced output to single-ended input, using an xlr-female to rca-male cable or adapter) should not be done with typical commercially available cables and adapters without careful investigation of whether the output of the particular equipment can tolerate having one of the two opposite-polarity output signals connected to ground.

Adapters and adapter cables used for that purpose will typically ground pin 3 (which on USA equipment carries the negative-going or "cold" signal polarity). Grounding that signal will result in improper operation or damage to the output stages of some equipment.

Regards,
-- Al

Shadorne - Not sure I understand all of your last post. Am I OK to use a RCA male output from my preamp and an XLR male input into the amp or do I need to include something else to avoid clipping? Thanks for the help.

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