Hi All,

Was using my denon DN-D9000 at the weekend. When pulged in to the pa a nice live hum/buzz from the epeakers. Pulged in out everything and found its the cd players. Checked the Plug and lead but no answers. Its housed in a wheel in flight case. ANy ideas ?

Tec

what cables are you using to link the cd player to the mixer.... it could be one of these or the mixer its self.....

but low level buzzing or humms are normaly down to bad mains power...

it could have been the socket you pluged the gear into... it could be the mains leads you used.....

try the cd player at home and see if it does it... i think you will find the fault goes away when you change the cables.....

Well Marky,

Tried the Plugs with different plugs and different gang lead. Also tried new XLR leads into the mixer.

I think this is a ground loop.

Try running the system with the sinal earth lifted temporarily.

NOT THE MAINS EARTH!! (Although this would probably eliminate the problem!)

If it were me, I'd start carefully checking the other units in the rack as well as the DN-D9000. I know you've already done preliminary checks on audio leads etc, but theres a strange anomoly which can sometimes creep into rack mount gear.

If one piece of equipment in a rack mount flight case develops an earthing/grounding problem it passes the hum on to other pieces of equipment in the same rack cabinet... it does this virtue of the rack mount tracks (where the nuts/bolts hold the rack mount gear in the case) are metal, and therefore conductive. Often, its possible even for other audio gear to develop a fault, and not suffer from it itself, but for the effects to be heard on other gear in the rack.

For example: A friend of mine had an old Rane 1 rack U Graphic Equaliser in a rack with an amp and a small mixer.

The mixer was giving out hum - you could hear it on the output, you could see the bottom two LED's on the mixers LED ladder flickering with the hum too. My friend wired around the equaliser to test it eg: connected the XLRs which normally went in and out of the equaliser, together....BUT left the equaliser powered ON....So...now the mixer was directly connect to the amp...but the hum was still there....visible on the mixer LED's. Turning the equaliser OFF, fixed the problem.

My friend opened the equaliser up next day, and found that the nut/bolt assembly which connects the Mains IN Earth cable to the casing of the unit, had loosened and had released its connection to casing.

Until he'd switched the Equaliser off, the mixer looked suspect. With no audio leads plugged into the equaliser, the only remaining connection was the metal rack mount tracks.

So, its well worth while removing the equipment from the rack, or at least, powering off all the rack gear and turning it on, just one item at a time. During the test, Feed audio to/from rack gear using an external device eg: a portable cassette deck, or second mixer etc.

Cheers Gary,
Will have a go at that tomorrow. Hopefully i'll be set for the weekend.

Fixed - Cheers all for the advice