How to get rid of monitoring speakers' humming?

[hkju2]

HELP!!

For some reason, without changing the hardware setup (002 rack) and the software setting(pro tools LE 6.4), both of my monitoring speakers started to generate consistent humming sound. Even after I turned down the volumn on the speakers, the sound still stayed. Is there anyway I can get rid of it?

Many thanks!!

Digi 002R
PTLE 6.4
Powerbook G4, 1Ghz
512 MB Ram

[mach-1]

A few things may be your problem.

Speaker wires or power supplies running accross powerstrips or other power sources.
Shareing the same circuit in your home or apartment with the refridgerator or like items.
Cables running across or very near to flourecent type lighting...
Poor quality cables.

Things like this create these issues 90% of the time.

think simple first. Then work towards the technical stuff

mach-1

[hkju2]

Hi,

Many thanks for your kind reply. I do make sure that they are not crossing any majoy power source, but the same humming problem is still happening. However, when I unplugged the firewire off the port, the humming instantly disappeared. Perhaps it has to do with the firewire connection??

h-k

[Jack Dawson]

Try unplugging all the audio inputs and outputs from the 002 (except the monitor circuit) and see if the hum goes away.

Jack

[albee1952]

If disconnecting the input cables makes the hum go away, it sounds like a ground loop. If you have balanced cables going to your monitors, clip the sheild connection at the monitor end of the cables. This will break the ground loop and you will still have sheilding as long as it is connected at one end.

[hkju2]

Hi Jack,

Thanks a lot! I just unplugged all the audio inputs and outputs except for the monitor circuit, but the hum is still here....the only difference it would make is when I unplugged the firewire cable. I also tried a different firewire cable which didn't solve the hum either....Whats really wrong??

h-k

[Jack Dawson]

Is it a 60HZ "hum" or a higher frequency "buzz"?
Did you add anything at all to the studio that might correspond to the onset of the hum?

Jack

[hkju2]

Hi guys,

Thanks so much for all your help!! Can you explain more specifically what "clip the shield connection" would entail?

Apparently, the hum is higher than 60HZ. I did add up some sofwares recently to the studio, which are dvd studio pro 3 and after efftecs. Perhaps they corrupted the preference?

h-k

[Jack Dawson]

I'm thinking ground loop also, but I've a few more questions.
What type of monitors are you using? Active or passive? How are they connected?
If you plug head phones into the 002, do you hear the hum?
Do you hear the hum whether or not Pro Tools is launched?

[hkju2]

They are self-powered speakers manufactured by audio phile. They are connected via two mono TRS balanced cables with the monitor circuit in the back panel of the 002 rack. When plugging into the headphone, the hum is still there. Whether pro tools is launched or not, as long as the powerbook is on, I hear the hum.

Can you kindly let me know how specifically to break the ground loop? Thanks so much....

h-k