Hey guys,

I have a question for the techies. I have an balanced output from an Audio interface that I want to feed to an unbalanced amp to power some monitors. Will this degrade the sound quality at all? Is the best way to do this with a balanced cable all the way to the amp, then an adapter at the amp end? or would a cable like XLR to RCA be suitable?



Thanks guys,

So your audio interface will only accept balanced output? Not unbalanced.

I will be using a DB 25 breakout cable to 8 TRS/XLR outputs.

Robb, whether you use a balanced cable with XLR plugs and then attach an RCA adaptor on the end or use a ready-made XLR-RCA cable should make no difference if both cables are similarly shielded. In either case the connection is unbalanced, since both the output device and the input device have to be balanced for a possible interference reduction advantage(not usually needed with a typical home level of interference)to exist. The balanced output sends out two signals(rather than the one on the central conductor of a coaxial cable)on the two conductors of the balanced cable with XLR plugs, but one of the signals is electrically inverted 180 degrees by the output device. Any electrical interference impinging on the cable is almost equal in strength on the two conductors and is in-phase on the two conductors. In the balanced input device the signal on one conductor is again inverted by 180 degrees so that the audio signals are in phase and instead of cancelling each other result in a 6dB higher signal(a doubling of voltage is 6dB). Any interference on the conductors, on the other hand, is cancelled by the inversion. Again, for most uses the interference rejection of the typical shielded coaxial cable used in an unbalanced connection is sufficient.

Wow, very well put.

Every forum should have a Johnk.

John, how much sound quality am I losing going from Balanced to unbalanced?

In short runs, I'd say there there is no sound quality loss. The job of balanced cables is to prevent electrical interference from effecting your signal. If the run is short enough and not running through any high electrical traffic areas than balanced cables don't provide any benefit except peace of mind.

Now that being said and knowing your a drummer, are you talking about this setup in a stage environment? If that's the case, the potential for interference from all of the other powered equipment, powerful speaker magnets etc.... could definitely justify the peace of mind coming from balanced cables. However, as JohnK pointed out, both the source and endpoints bust be actual balanced inputs & outputs to get the full shielding benefit of balanced cables. Converting to RCA half way would null such benefit.

Not my area of expertise though, I'm open to correction.

Are we talking stage monitors or studio monitors?

I know that I have run into a few situations where converting the XLR to an unbalanced signal has caused problems (over long runs) but if you are using this for what I think you are, you will be fine with the XLR-RCA cable. Alternatively, you can pick up a DB25 RCA breakout cable if you only need RCA connections.

Robb, there's no "sound quality" factor involved, other than the possible effect of electrical interference. Sometimes the added voltage with the balanced input(if the amp gain isn't lower on the balanced input to equalize)causes a louder volume at the same setting and is mistaken for things such as "better bass", "clearer highs", "wider soundfield", etc. which are simply due to the increased volume(a common factor with amplifier sound misunderstandings). If, as is usually the case, the shielding on a cable such as the MonoPrice item shown is adequate, then a balanced connection has no benefit. In any case, the point is moot since the amplifier here has no balanced input circuitry.

http://www.rane.com/note110.html

There are two situations when you can't transformer isolate unbalanced connections.

a) the circuit works best when the - of the balanced side is tied to ground.

b) the circuit works best with the - of the balanced side not connected to anything.

Some circuits don't care, and in others, the performance changes noticeably when it's done the wrong way. It depends on how the balancing is done.

There IS a "sound quality" factor involved, but only with say 10%(if that many) balanced circuits. Most don't care, such as mixer line ins - most people connecting unbalanced connectors are using typical 1/4" guitar cables where ring would be shorted to ground anyway, so it doesn't make sense to design a circuit where tying pin 3 to ground screws things up. I forget if the 10% of the circuits out there are the ones that mess up with pin 3(-) is lifted, or if they mess up when it is tied to ground. I guess that makes me an awful tech. But I have seen strange behavior with some balanced gear wired improperly to other unbalanced gear.