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Preferred XLR to RCA conversion for subs?

klettermann

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Mar 2, 2022
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My sub cable length is pretty long, about 30 ft, and there's a slight hum. The DAC feeding it has balanced and RCA outs, but Sub only has RCA input so that's what I'm using. Presumably a balanced interconnect would improve matters. Any thought on the best way to convert?? Transformer? One of the small active devices using opamps or whatever? Other? Comments welcome, thanks in advance.
 
Presumably a balanced interconnect would improve matters. Any thought on the best way to convert??
It would not.

As long as your Sub uses single-ended input, ground loop induces noises will remain likely, no matter if fed from an RCA output or XLR output.

In fact, trying to convert XLR to RCA can easily introduce a number of additional issues like increased noise, distortion, and DC offset, which would not happen with native RCA out.

One thing that could help is to break ground connections wherever possible.

A good place to start would be to feed the DAC via Toslink, and power it using an isolated power supply (e.g. phone charger).
 
Does the hum go away if you plug everything into the same AC wall outlet?
(move the sub or use a long AC extension cord)
 
It would not.

As long as your Sub uses single-ended input, ground loop induces noises will remain likely, no matter if fed from an RCA output or XLR output.

In fact, trying to convert XLR to RCA can easily introduce a number of additional issues like increased noise, distortion, and DC offset, which would not happen with native RCA out.

One thing that could help is to break ground connections wherever possible.

A good place to start would be to feed the DAC via Toslink, and power it using an isolated power supply (e.g. phone charger).
If an XLR to RCA converter is used (active or transformer) and located very close to the sub with a very short (eg < 15cm/6inch) RCA cable between the converter and the input, then noise should be dramatically reduced.

One of the small active devices using opamps or whatever?
Active - I'd be using something like this (if you are prepared to do a bit of DIY to put it in a box)

Alternatively perhaps this:
 
Thanks to all. I haven't yet tried the power cord and ungrounding stuff, but will. I'll probably get the converter too, just because. I want to run a sub cable to the rear wall anyway. It would nice to have both xlr and rca on the wall plate for possible future use. Cheers
 
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