Hum Help

[Zarven Kara]

Have been trying for weeks to pin point a hum from 0-70hz in my system. Cant get rid of it!!!!! Any ideas? Its on all mic's Condensors, Dynamics and Ribbons. Different Pre's makes no difference. All other power outlets shut down from the mains and still nothing. Just mac - Lynx Aurora - pre - mic . Anyone got any ideas? Would be much appreciated, frustration overload....

Cheers

[Zarven Kara]

Electrician grounded directly the powerpoint that the equipment runs off.. nothing

[simonstav]

Turn the lights off, does it go away?

[Zarven Kara]

Hi Simon, no lights still there...

[simonstav]

need to substitute components, converter, cables, etc until you track down the culprit.

[Paul Maybury]

How is the computer grounded? Is it grounded?
Are your signal cables grounded at one end only?
Cheers, Paul

[Sammas]

Is there any chance it is atmospheric? Low frequency rumble that is being picked up by the microphones? Things like local traffic, train lines, etc can cause it and often it is only noticeable through a microphone - not simply by standing in a location listening by ear.

[Junction]

This is an earthing issue, often quite difficult to solve. The first step is a process of elimination - can you plug in all the minimum amount of gear involved into one power point only (console, PC, audio interface) or whatever is in your basic setup. Use headphones into your console instead of a powered monitors. Is the hum still there? If it is still there, then maybe one item of gear is not earthed, whereas others maybe. If the hum isn't there, then you could try moving one of items of equipment on to another power point circuit and then re-check if there is hum. This might be just the start of the fault finding process, see how you go.

[Zarven Kara]

I've taken the system into another isolated room and the low end is still there. I have the shield of the microphones grounded at both ends. Im not sure how this system works of not grounding one end. If I remove the shield ground it just makes a noise as if the mic isn't grounded. Does the end at which you remove the shield matter? Definitely not atmospheric. The studio is in the bush and have had the mic in a isolated box.... Computer is not grounded... might also be a component issue with the pre there is also white noise that I need to get rid of, perhaps re cap? Its an amek 9098...

[Gian]

You need to isolate each component one at a time, adding each component to the "system" one at a time and checking.

Can you run the mic into a laptop running on battery and check on headphones - so no mains is being used?

Then when you know the mic is good, connect it to the preamp into the laptop running on battery.

Connect the laptop to the mains and see what happens.

etc.

[Paul Maybury]

Hi, the mic cable will need to be grounded at both ends because the mic is not connected to anything else. So the mic cable is effectively grounded only at one end, the mic pre end.
I think you may find the problem is that your computer doesn't have an earth connection. Try connecting it to an external screen that does have a mains earth connection. That will at least tell you if the computer grounding is an issue.
Best of luck.
Paul

[rob]

Following on from our emails.
is this a real world signal to noise issue as determined by listening to real recordings played back at realistic levels.

or

is this a spectrum you are seeing on an analyser following maxing the gain.

There is noise in everything. What counts is signal to noise.

failed capacitors do not make excessive hiss