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Very strange hiss / background noise
Old 12th January 2013
  #1
Gear Maniac
 
🎧 5 years
Very strange hiss / background noise

Hey guys,

I have a pair of JBLs hooked up to the same power source.
My PC, to which my interface is hooked up via USB, is also on the same power source.

I have the monitors connected to the interface via XLR cables with a Neutrik XLR to cinch converter, functioning very well.

The issue is that the converters were too big for the small space between the L and R jacks on the back of the interface.

So smart me I decide to go XLR to cinch directly, so that everything is plugged in nice and clean.

Since then, I hear a very distinct hiss / white noise from both speakers; it's the same noise source because the noise seems to come from above my PC monitor while my monitors obviously sit on either side.

The noise is there even when the PC is off (=> interface off). It's also there when all the other plugs are taken out of the plug rack where the speakers are connected.

What's bugging me is that nothing changed besides the cables which are decent quality Quiklok AD52 cables.

Do I need to return the cables or is there anything else I could do to make the noise go away?

Thank you for your help.
Old 12th January 2013
  #2
Lives for gear
 
🎧 15 years
Hi
Try ferrite cores. Available as 'clip on' so you don't have to cut cables or solder.
Could also try ferrite rod taken from old AM radios. Wrap your cable around the rod as many times as possible.
Matt S
Old 13th January 2013
  #3
Gear Maniac
 
🎧 5 years
Thanks for the suggestion.

But why changing the cables produced this side effect?
Old 13th January 2013
  #4
Lives for gear
 
🎧 15 years
Hi
If it is 'RF' noise which is being introduced to the monitors all manner of things can affect it. Cable length possibly being an important one in this case. The actual screening properties of various cable types is probably quite similar unless you are using the special 'RF' double screened stuff intended for very high frequency operation.
Physical routing may also have an impact.
I am presuming you are saying that the connectors on the monitor amplifier are cinch type, or are they the 'XLR' end?
Please say what is on which. It may be the pin 2 and pin 3 need to be joined in the XLR as cinch are unbalanced and if it is picking up RF it may be sensitive to where things are 'grounded'.
Matt S
Old 13th January 2013
  #5
Gear Maniac
 
🎧 5 years
Monitors have female XLR and interface is cinch L+R.

New cables are 2x longer because the other ones were too short for where I wanted to put my monitors.

Thing is, older way of connecting monitors to interface was:

Monitor XLR F - (Cable XLR M - Cable XLR F) - (Neutrik connector XLR M - Neutrik connector cinch M) - Interface cinch F.

Couldn't find out if the cables were balanced or not, manufacturer and distributor sites did not have that information; however, the cinch on the new cables have 3 black rings on the metal sleeves, does that mean anything?
Old 14th January 2013
  #6
Lives for gear
 
🎧 10 years
You might as well use cinch/RCA cable on both ends. If your interface only has RCA outs then its unbalanced. (2 conductor)

Using a RCA (2 conductor) to XLR (3 conductor) is still unbalanced. So XLR on the speaker end is gaining you no benefit over using RCA cable on both ends.
Old 14th January 2013
  #7
Gear Maniac
 
🎧 5 years
Monitors have XLR and TRS, interface only has cinch/RCA.
Old 14th February 2013
  #8
Gear Maniac
 
🎧 5 years
Me again :-)

I put ferrite cylinders around both monitor cables (right outside the connection to the interface).

No dice

What's next?

I noticed that the noise becomes stronger when the computer boots.

Help!
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