Axiom Home Page Forums General Discussion Advice from Axiom Owners Balanced or unbalanced amp inputs?

What’s the function/difference with these two amp inputs on my 1080, or any amp for that matter?

Mike, a balanced input acts on a "differential" basis, i.e. it subtracts the signal on one conductor from the signal on the other. The result is that any signal that was exactly equal on both conductors would be completely cancelled. When outside interference hits two very closely spaced(often twisted)conductors the noise signal is nearly the same in both conductors and the noise is therefore almost completely cancelled in the balanced input. The music signals themselves are positive and negative on the two conductors and subtracting a negative is the same as adding it to the positive, so the desired music signal isn't cancelled, while the unwanted noise is. So, the balanced input has an inherent resistance to interference, even if the connecting cable isn't shielded. This is often preferred in professional applications involving long runs near sources of interference, so the XLR connectors to the balanced inputs are used instead of RCA plugs. As a practical matter in home use the usual shielded coax with RCAs to the unbalanced inputs has no significant problem with interference and the balanced inputs wouldn't bring any real benefit.

....plus, you won't be able to use balanced with your RC-1070 (unless you use hybrid, which is not recommended). RC-1090 does have balanced outputs though, and should couple better with RB-1080...

John, what type of noise would one expect to have, under what circumstances?

Thyname, I was wondering how that would work while I was reading John’s reply. Like you said, the 1070 has coax outputs. One thing I found a little odd, was that the 1080 has the inputs located at opposite ends of the unit, and not close together. I had to split my coax cable to reach them. Is there a particular rational behind locating them this way?


Thanks……..mike

Mike, first maybe I'd better re-emphasize that if we use the ordinary reasonably well-shielded coax, we shouldn't "expect" any noise. Be that as it may, coming through the air(i.e. the power supply isn't involved)might be electro-magnetic interference(EMI)or radio frequency interference(RFI)to impinge on the cable. The EMI is lower frequency stuff such as the 60 cycle hum induced from running a power cord in contact with the cable for a considerable distance, fluorescent lights, electric motors nearby, etc. RFI is higher frequency hash from very powerful and/or nearby transmitters.

Yeah, if you have a 1070 without balanced XLR outputs the discussion is pretty much just academic. Gave some thought about the widely separated inputs on the 1080 and didn't come up with anything sensible. Putting them both together near the center would need a few more inches of internal wiring, but that's insignificant.