GP-510 Line-In vibration/resonance issue

[Morrowless]

I'm trying to output Pianoteq sound through its internal speakers but on a key press, depending on the note/frequency I hear this annoying vibration/resonance. I don't know if there is a proper word for it, but it's the same sound an acoustic piano makes when a certain object in the room vibrates responding to the piano sound. 

Now when I listen to the notes using headphones (connected to Pianoteq), there is none of this sound. So it's not a Pianoteq issue. It's only when I use the GP-510's internal speakers through Line-in.

If I just use GP-510's internal sound engine, the speakers do not produnce this annoying sound. I suspect it's something inside the Line-in component.

Any similar experiences or tips to fix this?

 

My setup: GP-510 ---USB---> Raspi + Pianoteq ---USB---> Topping D10s --RCA to 6.35mm---> GP-510 LINE-IN

 

EDIT: after a bit of research I found out that mismatched impedance can cause audio distortion. The GP-510 line-in is 9000Ω, while the d10s is only 20Ω. Is that a problem? I'm in over my head with these audio terms...

Edited February 14 by Morrowless

[Brad Saucier]

Have you tried headphones directly connected to the GP-510?

[Jokeyman123]

I suspect the Topping D10. 

 

Are you using the balanced or unbalanced version of the D10? If it is the balanced (TRS-3 conductor) version into the GP-510, this can cause a mismatch in signals. If you are using the version with RCA outs, should not be a mismatch but 20Ohms-very efficient-may be too efficient for the GP line input. 20 Ohms means it is very sensitive-presents no resistance to whatever is connected to it, so the D10 might be overdriving the line input of the GP-510- it is outputting at 384Khz and has a dynamic range of 125DB which is very "hot". This is excellent as an audiophile spec, but it might be too much for the GP-510 line input and could be causing excessive harmonic overtones, at least for the GP-510. A high-spec audio amp/preamp could handle that dynamic range, but the D10 might be overdriving the GP-510 line input. I know this all might sound like gibberish-but it isn't!

 

If you have a different USB to audio interface, try it.  I'm also always a little wary of USB in a system like this-where you are outputting GP-510 midi data into a computer-then using the same USB connection to connect a line-in audio signal. The D10 interface may or may not eliminate any feedback loops from the USB configuration you are using, but.....make sure your USB connections are tightly connected and should be shielded with good heavy duty cables if you can.

 

I assume by Raspi you are using some kind of Raspberry Pi midi interface? 2 USB midi interfaces in the same signal chain, also could present distortion, but my best guess is the D10 overdriving the GP-510. It may be creating or amplifying additional harmonics the GP-510 is not designed to deal with.