sligh high pitch noise from AT897 when on cam

Chakra5films wrote on 5/29/2005, 10:06 PM

Hey guys - somewhat of a newbie question here.
Decided to finally upgrade my audio options and bought the AT897, the Beachtek 2S and respective shock mounts. I'll obviously be usng the AT897 primarily on a boom, but when I do mount on my cam (gs400), the voices are quite clean, but I am getting a slight higher pitch noise that runs constant throughout.

Here are my settings:

manual audio on cam - no AGC
Mono setting on Beachtek, with both channels turned all the way up (no, turning these down did not help)
Grounding set to G1 (G2 did not change anything)

I know these are difficult to answer on a message board and not looking at it in person, but any advice or experience on settings would be greatly appreciated.

Thanks to all on this great forum for your help.

Comments

farss wrote on 5/30/2005, 3:13 AM

First off I'd try to see if it's from some form of ground loop as you've now electrically connected the Beachteck and the camera so just try it with the BeachTek dangling on the side of the camera.
If that doesn't help (and I suspect it will not) then it could be the mic picking up mechanical noise from the camera, unclip the mic from the camera and slowly move it away from the camera.
One of two things might happen, as soon as you unclip the mic the noise goes, this could be one of two things in itself, you've broken the electrical connection between the camera 'groung' and the mic or you've broken the mechanical connection between them. If that hasn't changed things much then maybe as you move the mic further away from the camera the noise slowly abates. If that's the case then the mic is picking up mechanical noise from the camera.
If the later is the problem then it's pretty hard to fix, you just need to keep the two apart. In any case it's a good idea to have some separation anyway to avoid picking up all sorts of noises from the camera like; you using it, zoom and focus motors etc. Of all the places to have a microphone, mounting it on the camera is the worst.
Bob.

rraud wrote on 5/30/2005, 8:26 AM

Could be some kind of electrical RF/EM interference. Make sure you are using good quality sheided mic cables, correctly wired: (pin 1-ground, pin 2-hot, pin 3-neg).
Shut off any phantom or bias power if the mic is battery powered. If there is bias power present you may need to install a capacitor in the mic cable connector.

A grounding problem usually manifests itself in a 60hz low frquency hum.

Chakra5films wrote on 5/30/2005, 10:36 PM

Great guys, thanks

I'll try your suggestions tomorrow morning. I realize that mike on cam is just asking for problems anyway, but there are a few occasions where I'd like to get a relatively clean track.