[sdiy] Noise from a (perfect) Yamaha CS50

[Antonio Tuzzi]

Hello friends


I have a friends with a Yamaha CS50 that is noisy when connected in his studio
is clearly present in the audio kind of GND effect



but is perfect when used in another studio (or when he brings it to the techician, that say : IT'S PERFECT!)


what could be the problem ? (GND Loop problem ? but why only with the cs50 ?)
and why only with this keyboard ?

and what he can do to solve it ?


ciao

Antonio