Connect PC and headphones to digital piano

Question

It has become my hobby to write my own piano arrangements for songs I like, but due to my furniture arrangement, I couldn't connect my digital piano to my PC - until now.

Now I'd like to have just one pair of headphones to listen to the original song (from PC) and my own playing (from piano), sometimes simultaneously. My first thought was to connect the piano's line-out to the line-in of my PC, but there is a huge delay (feels like 500ms) that makes it impossible to play. Tinkering with the settings and installing ASIO4ALL and JACK didn't help enough because there still was a small delay - much better compared to the delay without ASIO, but it still made me uncomfortable to play.

So I bought an external audio interface (Behringer UCA222) which has a line-in for my piano, a monitor output for my headphones and a USB connection to my PC.

I don't think this is common, but my piano (Kawai CN-3) has a line-out which is not only controlled by the piano's master volume control, the line-out is also muted when I connect headphones. So I have to connect the interface's line-in to the piano's headphones output if I don't want to disturb my sleeping son because I can't mute the piano without also muting the line-out.

And now I have another problem, and I don't know whether it's the piano, the headphones, the audio interface, or the fact that I had to use the headphones output. When I play a bit louder, especially when I play many notes at once (e.g. glissando or series of 4-note chords with pedal), there is a scratch sound in my headphones which sounds like an overdriven/clipped audio signal. First I thought it must be the interface because I never had problems when the headphones were directly connected to the piano. But when I use Adobe Audition to record what I'm playing there is no clipping at all (all input levels set to 100%). Even if I turn down the piano's and the monitor's volume, there is sometimes a scratch while Audition shows a maximum level of -15 dB.

Unfortunately, I don't have another piano or even other headphones to try. Does anyone have an idea what I'm doing wrong?

Answer 1

First off; Behringer is garbage. Always has been, always will be. Your noise ("scratching") issue sounds like badly-written zero-latency monitoring drivers. Or, those phono inputs are almost certainly not grounded so they pickup stray voltage from (wherever).

Buy an m-audio (2 channels for about $100) or, if really squeezed for cash an ART ($60 or so). Definitely get 1/4 inch or xlr inputs and external psu (powerbrick) if possible. At that range, harder to get independent ground (3-pin power cable) but better than usb power for sure.