Balanced vs unbalanced

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Balanced vs unbalanced

Postby chris p » Mon Sep 05, 2005 11:36 am

I posted this question on the FMR RNLA thread but that got frozen before anyone could respond. It arose from my wish that the FMR RNC had balanced inputs/outputs, to which a couple of people replied pointing out that it was easy to connect balanced to unbalanced equipment (and vice-versa). However, my problem is not an inability to solder, but rather my understanding as to why balanced lines were invented in the first place.

I am willing to stand corrected, but balanced cable gives better RFI rejection, yes? So working (as I tend to do) in places with flouros everywhere, isn't there a diff between balanced and unbalanced cable runs, even short ones, as potential noise sources?

Also, my understanding of the most simple balanced to unbalanced wiring effectively unbalances the whole cable (rendering it liable to RFI), unless you get into an isolation transformer at the unbalanced end (and that's what I didn't want to get into for the sake of a $300 compressor).

I'd love to learn that I'm wrong on this. I can certainly solder up the odd cable or two if there's no sonic value in staying balanced.
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Postby michael » Mon Sep 05, 2005 12:34 pm

yeah my understanding matches your understanding.

But i would comment on this in a couple of different ways -
- I HATE fluro lights if it's your place or you have a say in it I would do something about those.

- secondly i use unbalanced gear and it's important to realize that unbalanced doesn't mean you WILL get interference, just means it's more likely. I use some unbalanced stuff and don't have a problem. You can get too carried away with fearing unbalanced in my opinion. Guitar leads, some keyboards and other gear making the music are all unbalanced.
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Postby mfdu » Mon Sep 05, 2005 4:48 pm

there doesn't need to be an issue. just make your own cables. keep it balanced up until the point where it hits the unbal and (from memory) drop the earth at the unbal end.

the lower the signal level, the more the balancing of the cables comes into play - more susceptable to noise pick-up. the more other cables and power lines the poor signal has to cross over, the more chance of noise pickup.

dont forget the + or - 6dB going bal to unbal with the wrong cables.

why balanced? (other chris's, feel free to correct me - this is how i understand it) :
the +ve and -ve of a balanced cable are phase reversed. any noise picked up in the cable length will therefore be exactly 180 out of phase, and will henceforth be cancelled out when the two signals are combined at the recieving end.

do i pass?

chris.
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Postby Chris H » Mon Sep 05, 2005 5:42 pm

mfdu wrote: (other chris's, feel free to correct me - this is how i understand it) :

do i pass?

chris.
...............

I'm no adjudicator on technical matters. I think every time i throw in a tech perspective i only prove my own ignorance.

What i do is use guitar lead cable instead of mic lead cable and link pin 1& 3 of the XLR. The shield goes to pin 3 (&1 because of the link) and the other goes to pin 2. The other end is usually RCA or phono so shield to sleve and positive to tip.
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Postby mfdu » Mon Sep 05, 2005 5:59 pm

thanks chris h - i knew you'd be out there somewhere. proving my own ignorance isn't something i like to do on my own!

that trick you mention is fine using unbalanced cable. i guess thats what folks are wanting - save some cash with just a hot/earth rather than hot/cold/earth.

i had jumped in thinking i could help by mentioning the actual bal>unbal, and i just want foks who haven't thought it through to remember that potential 6dB drop going unbal>bal.

this has come up a few times with me, because folks have asked me "why is my 002 input so low?" . . . because it's fully balanced except for the RCA doubles of 1/2 out and 7/8 in.

and it's almost time for me to grab my skateboard and get on home for an evening of voice-over editing.

:)
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