grounding problems in Clavinova Lab

[spg6611]

I have recently connected 13 Clavinova 201 to PC Computers for use in a keyboard lab. The lab uses the Clavinova controller MLC 16.

I was unable to use the serial cable provided by Yamaha for connection to the computer because it caused a 60 cycle hum that was heard through the headphones, but not through the speakers. Instead, I connected them using MIDI cables and a MIDIMAN interface.

Everything was working great. Then I connected the sound card from the computer to the Clavinova using an audio cable and this is causing the same type of hum.

The hum is a problem on only 1/2 of the stations, all on the same side of the room, probably on a different circuit than the rest of the room.

I have tried the obvious thing, a three to two prong adaptor with no success. I have also experimented with plugging things in differently. However, nothing works.

Does anyone have any advice?

Susanna Garcia

[wally]

My first initial thought is that if the humm is evident on only one side of the room, then you may have a grounding problem with your electrical outlets on that side of the room. Use a ground tester to see if each power outlet is properly grounded.

Once you've done that, make sure that your cables are properly grounded. That should solve your problem.