Removing noise from RCA cables to monitors

[rkb2948]

I'm currently experiencing what sounds like EMI/RF noise. I'm running a Modi usb DAC to my KRK Rokit monitors using an rca cable. I tried twisting the wires a bit, but it didn't seem to work. Everything is connected to the same power strip, and it seems totally random. Any ideas on a quick fix?

 

[jaddie]

Grab one of these, connect it between your DAC and monitors.  You may need adapters...
 
http://www.radioshack.com/product/index.jsp?productId=2062214
 
If the noise goes away, post here, I can recommend something a bit better for permanent use, but this is a cheap, almost for-sure fix.

 

[rkb2948]

Doesn't a ground loop typically result from connecting things to different outlets? In my case everything is connected to the same power strip (computer, speakers, everything). Its not a constant noise, its somewhat intermittent; occasionally silent, but typically noisy. It seems that maxing out the volume out of my DAC seems to minimize the noise, at least relative to the music.

 

[jaddie]

Many PC power supplies place noise on their ground bus, which if it is also audio ground creates issues like this. Try the isolator, if it works you've found the problem, and it's always returnable.

 

[rkb2948]

Color me surprised, but you were right. The isolator fixes the problem.
 
Many thanks!

 

[jaddie]

No prob.  I keep a couple in my tool kit for making instant happy clients.  Pretty much works every time.
 
Now, if you want something a bit higher performance, there are better equivalent devices, but overall the Shack thing isn't bad at all. Certainly none cheaper!
 
This is about as good as it gets:
http://www.jensen-transformers.com/ci2rr.html
 
Priced at $177 a copy, but for the ultimate in quality this would do it.  But, the 80:20 rule applies.  You get 80% of the value for 20% of the price, pretty much every time.  So I'd stay with the Shack device unless you get an  OCD flare-up.

 

[rkb2948]

As best I can tell the radioshack thing is a 1:1 transformer, no? That shouldn't have any negative impact on sound quality right?

 

[jaddie]

Quote:

As best I can tell the radioshack thing is a 1:1 transformer, no? That shouldn't have any negative impact on sound quality right?

Yes, it's a 1:1 transformer.  Transformers are not always "transparent". They can add distortion of various kinds at various frequencies and conditions, and limit frequency response.  Their specific ability to reject noise is also a variable, it's a rejection ratio vs frequency.  Most are good in the low audio band, some good through the entire audio band, most fall apart in the RF frequencies. 
 
But hey, don't obsess.  That little thing is darn good.  I've never felt the need to measure it because it works so well and never sounded at all bad to me.  I'll put one on the analyzer some day.

 

[jaddie]

Did a couple of quickie tests on the Radio Shack isolator.  It's not half bad.  From mid bass and up it raises distortion just a tiny but, not audibly.  At extreme bass at high levels distortion can come up to nearly .5%, but that's at 20Hz and 3 volts, which you're not likely to hit.  What's going in is called transformer saturation.  It's one way the high-priced units would be better.  Channel separation is excellent, frequency response is also quite good, dropping only a tiny at the extremes.  
 
The tests explained why I never felt the need to test it. Virtually no audible insertion effects.