When Recording....

[Orgrinder010]

Every once and a While I will record a track, maybe ten minuets or so, and when I play it back there is a very Noticeable Buzz that can be heard. I would imagine its around 60Hz. Whenever this happens, I just feel like throwing the Mic Preamp out the window. Is there any plug-in filters that remove this? I use Sony sound forge.

[PeteKnobloch]

I don’t know about any software filters, but back in the1970’s, I bought a pre-amplifier from Radio shack that had that very problem. When I opened up the box, I found that the common wire from the power supply module was soldered to a lug (Signal Ground) that was physically placed between the rectifier and the main filter capacitor. For every cycle on the AC line, there was a pulse of current going through this run on the PC board that recharges this capacitor. This pulse was being amplified by the pre-amplifier. I moved the wire 1inch electrically and connected it to the capacitor directly. The 60Hz noise totally disappeared.

[andyg]

Assuming that the mic preamp is mains powered, this sounds something like an earth loop. Check that the preamp and the recorder aren't both earthed. Try using a balanced mike and balanced leads between the preamp and recorder. Sound Forge should have a hum removal tool, either built-in or as a plug in. Andy G

[wombat11]

Hi Andyg,</p>

I`m back-it`s your old mate,wombat.</p>

Just got back from an exhausting holiday in America-everything certainly is big out there?!! </p>

Yes,it does sound like an earth loop or bad connection,organgrinder010</p>

Well,all for now,I`m orf to `ave my cup of cocoa(am I a sad old ..t?)</p>

wombat11
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[quantum]

I use Audition (there is probably an equivalant procedure in SoundForge). If I find that the hum removal filters can't remove the hum completely, I switch to spectral view where frequencies are plotted on a colour graph of time/frequency/intensity. If there are any horizontal bands running across the graph, this is usually hum. It is possible then to zoom in the graph, find the frequency range, then using an appropriate filter reduce gain in that range.
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