I currently own a PSR-640 keyboard.

When I connect the "Aux Out L/R" to my the line connection on my mixer, and have headphones plugged in, I do not get any noise. When I then connect the "Stereo Out" to my computer's line-in for recording the output, a distinct HUM is heard. If I disconnect the 640's lines, the hum is gone, reconnect, and it's there again.

So, for some strange reason, when I have both the 640 and the "Stereo Out" connected to my computer's line in, I get a HUM noise. Funny thing is, I also own a DJX and I also have this plugged into the mixer, and I get none of this noise -- even with the Stereo Out connected!

I've tried also connecting the headphone out to the mixer, and same thing. I've tried plugged in the power supplies to the mixer and 640 to other separate jacks, but still no luck.

It's either the 640 or the computer that do not like each other. What's going on here? Why would the DJX not make noise and the 640 do?

Any help would be much appreciated!

Bryan Nicalek
ptshpboy@hotmail.com

Hi Bryan,

Does the PSR have a 'ground' in the power cable ?
If yes you should try to use a power-socket without a 'ground-pin'. (Either the computer or the PSR) ,

In Holland we have two types of power connectors :
One with- and another without the GND connection. In many cases my tip can help.

kind regards,

Roel

What you probably are experiancing is a "ground Loop" Ground loops can occur when 2 or more electronic devices, with seperate power supplies are connected together. Simply put, a portion of the AC line signal is transmitted through the ground connections of the instruments, causing the hum. Ground loops are so common, and such a problem, they are one of the reasons thaat professional recording equipment uses 3 wire "balanced" connectors. They are also the reason many keyboard amps have ground switches, which let you change aspects of the ground connection. Hardware ground loop eliminators are available, and do a good job. You can find them at professional audio suppliers. A good UPS (uninteruptible power supply) can also eliminate ground loops, connecting your computer to one will isolate it from the incoming mains power, thus breaking the loop. The fact that your DJX doesn't suffer from the ground loop is just do to the fact that in some small way, its circuitry is different, so in your particular setup, it doesn't create a ground loop. Such is life, and the nightmares a sound engineer's life are made of...
Dave Waldman