Connecting keyboard to audio interface

[Foxtrot3]

I've got a Kawai MP7 that I want to connect the line outs to the RME Babyface Original (Not the Pro). This means that I need to connect 2 x 1/4" unbalanced mono TS signals to the 2 x XLR mono inputs in the RME for an overall L&R stereo input into the interface, and I was just wondering about what kind of cables I need to use to avoid ground hum or any noise.

 

Here's what the RME Babyface manual says about the 2 x XLR inputs.

 

"The Babyface has two analog microphone inputs that can operate as line inputs with levels up to +12 dBu, when set to 0 dB gain. The electronic input stage uses a servo balanced design which handles unbalanced and balanced signals correctly, automatically adjusting the level reference. When using unbalanced cables with the XLR breakout cable: be sure to connect the 'ring' contact of a stereo TRS jack, and pin 3 of a XLR jack, to ground. Otherwise noise may occur, caused by the unconnected negative input of the balanced input."

 

It seems to me that I therefore can't simply use my 2 x balanced 1/4" TRS to XLR cables that I've currently got, as it would introduce hum, is that correct? If so, what cables should I be using instead? I ideally would not want to use a DI box to convert the unbalanced signals from the Kawai MP7 to send to the Babyface audio interface. I've read a variety of conflicting advice in other forums, such as using "pseudo-balanced cables", simply using a TS to XLR cable as opposed to a TRS to XLR cable, and other pieces of advice that is going way over my head for me to try and comprehend.

 

Appreciate all the help I can get.

[PianoMan51]

When you try it, does it hum?

[Markyboard]

Since your MP-7 uses unbalance outputs the ring contact will be 'floating', i.e. unconnected. Theoretically it"s susceptible to noise. But I would try it ( your original balanced cables) and if you don"t detect any unexpected noise it"s fine. If you do than probably best to use unbalanced TS plug on one end and xlr on the other.

[Dr Mike Metlay]

RME tends to be pretty good about getting the best quality from whatever cabling is hooked up. My call would be to not overthink things too much. Use balanced TRS to XLR, and only worry if you get artifacts you don't like. If it sounds OK, then it IS OK.

[Foxtrot3]

Thanks for the replies everyone. Giving it a try and if it doesn't have problems, then it's working sounds like solid advice.

 

I have tried the 2 x balanced 1/4" TRS to XLR cables and there seems to be some sort of hum unfortunately. It seems like another option is required. What should be the next step in fixing the hum?

[Markyboard]

We get this question a lot. Are there other devices in addition to the Babyface, MP7 and presumably monitors and computer? The 'hum' may or may not be related to the cables we"ve discussed thus far. If you can give us a detailed description of your set up and connectivity we may be able to help. Even better if you can do a video showing the setup.

 

The basic approach is to eliminate connections until the culprit is found. Ground loops can be tricky if it turns out to be the problem.

[jazzpiano88]

Thanks for the replies everyone. Giving it a try and if it doesn't have problems, then it's working sounds like solid advice.

 

I have tried the 2 x balanced 1/4" TRS to XLR cables and there seems to be some sort of hum unfortunately. It seems like another option is required. What should be the next step in fixing the hum?

 

The transformer of a DI decouples the two. You might try or borrow a cheap one to test out for your setup and then decide if the hum is reduced. Then you could even upgrade to a really nice warming DI like the Radial JDI with the Jensen transformer. .