• gouda
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  • Registered: 2010-09-09
  • Posts: 9

Topic: Fireface UC and unbalanced instrument cables

Hi all,

Brand new owner of an FFUC here and loving it so far. Coming from a much cheaper interface, this piece of RME gear is amazing so far.

I have a question about the UC instrument inputs and using balanced vs unbalanced cables. I'm hoping someone can educate me so that I understand what's going on here (I'm not an expert at all yet).

In the manual, for inputs 1 and 2, it says:

"The two combo jacks also allow for the usage of mono and stereo TRS jacks."

.
Does this mean that only balanced/TRS cables should be used with inputs 1 and 2?

At first, I was using an unbalanced cable with input 1 and 2 and I was hearing a really annoying high-pitched whine. I also tried inputs 3 and 4 with an unbalanced cable, and got the same high-pitched noise. I tried a few different unbalanced cables and a few different instruments (Minimoog Voyager, electric guitar, bass), and the noise remained. It was definitely more noticeable at higher gains levels -- i.e., more so with the guitars than the synth -- but it was there for all of the instrument/cable combinations. I did discover, for inputs 3 and 4, if I enabled "Pad" and "Inst", that seemed to get rid of the noise.

I finally decided to read a little in the manual, and I noticed the info about using balanced cables. In addition to what I quoted above, there was also this note for inputs 3 and 4:

"When using unbalanced cables with TRS jacks: be sure to connect the 'ring' contact of the TRS jack to ground. Otherwise noise may occur, caused by the unconnected negative input of the balanced input."

A few more questions:

What does it mean "be sure to connect the 'ring' contact of the TRS jack to ground"? I'm guessing I wasn't achieving that, which is why I was getting a high-pitched whiny noise.

Is the moral of the story here that I should be using balanced cables for all of my instrument/mic connections, inputs 1-4?

Thanks in advance for any help anyone can offer. Much appreciated!

  • gouda
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  • Registered: 2010-09-09
  • Posts: 9

Re: Fireface UC and unbalanced instrument cables

/bump

Someone? Anyone? I know this a n00b question, but surely one of you has a quick/simple answer?? Your help would be very much appreciated!

3 Reply by Lomaxx (edited by Lomaxx 2011-02-04 09:39:10)

  • Registered: 2011-01-25
  • Posts: 32

Re: Fireface UC and unbalanced instrument cables

I am no expert myself, but the part with "be sure to connect the 'ring' contact of the TRS jack to ground" refers to how the wires of the cable are to be soldered to the plug of the cable, when making your own connection-cable or modifying an existing one. At the very end of the FFUCs manual you can find a little mor information about it.
Without any warranty (as already said i am no expert): I suppose the "ring" of the stereo-TRS-plug to be the small part in the middle of the three sections, which usually transports the 2nd audio-channel. If that ain't connected to the shielding you might occur strange noise within an unbalanced connection.