+48v buzz problem

[nuss]

I hope someone can figure this out.

I have a Behringer MIC2200 mic pre and as soon as i engage the phantom power w my AKG C1000s, i get a horrible humming buzz.

I know that it is not a problem with my mic cause i can use the phantom power from my console and it is noise free.

Could it be possible that the cable run is too long for the behringer to adequatley send the voltage? (cable run is almost 120')

Any other suggestions (other than the obvious:Behringer is broken) would be greatly appreciated!!

Thanks!

[Blue Bear Sound]

It's DEFINITELY NOT supposed to do that....
Try a shorter cable and if it still does that - your Behringer IS broken...

Bruce

[enemyofthesun]

is the device (preamp) producing the 48 grounded properly? I had this problem before.

[jgourd]

Are pins 1 & 3 crossed in one of the cables used to make a 120 ft run?

[nuss]

Hmmmmm.....grounded properly? Whats the easiest way to check that?


Are pins 1 & 3 crossed in one of the cables used to make a 120 ft run?


Shouldnt be....my console +48 works fine on the same cables.

Now Im wondering about the ground.........................

[Harvey Gerst]

The 48 Volts of Phantom power is DC so that shouldn't be the source of the buzz. With the cable plugged in at the mixer end (phantom power on), and no microphone connected, you should get a reading of 48 VDC between pins 1 and 3, and a reading of 48 VDC between pins 1 and 2. There should be very little (if any) voltage between pins 2 and 3.

Wwith both ends of the cable disconnected from the mixer and the microphone, you should have a continuity reading of close to zero ohms between pin 1 at one end of the cord and pin 1 at the other end of the cord (a dead short). There should be no reading between any of the pins.

If your cable run is made up of several shorter cables, start with just one cable and keep adding cables till the buzz appears - when it does, that's the bad cable.