Hum on live recording

[mediaguru]

I am using rca from the board to my laptop and Audacity to record the sermon. There is a hum from my projection computer to the board that Audacity picks up. I've done everything I know to eliminate the hum to the board but can't isolate it. Until I can find a solution I'm muting the out for the computer.

[[Admin] osborn4]

We ended up getting a USB sound card (something from Creative Labs) and a good stereo Direct Box to hook the sound from the projection computer up to the sound board.

Does the sound end up other places, like your mains? You may need some sort of hum suppressor between the sound board and your laptop.

[stevegoad]

I've had a lot of problems with hums while recording from my laptop caused by ground loops - the only thing I have found is to run the recording laptop on battery so that I'm not on the circuit with the board itself (lifting the ground often times doesn't seem to stop it). It definitely limits time, but gets a better sound quality.

[fwright0408]

Have you tried using a grounding plug for you laptop. That took care of the problem for us!! Also, are you using a direct box out of your computer (laptop &/or desktop), that should also help.

[acicomp]

We had the same issue. I had to make a decision to either make a monstrous investment on all new electrical with isolated grounds or use another method to remove the hum. The first option would have been the BEST solution since it would have isolated grounds for all of our AV equipment. HOWEVER, the budget wasn't there so I did a couple of things to "patch" a fix and remove the hum off the laptop.

We started with running off the battery only and this actually worked. The only issue was a dead batter in the middle of the service. Ok, so scratch that idea...

FINALLY, you can get a ground loop isolator from Wal-Mart or RadioShack. (Part numbers and links below I hope) I put one on both sound in and sound out of the laptop to always ensure that I had no hum. Some people also claim their DVD players cause hum as well. Many times, a projector will be on a different circuit and the ground potential will be different between the projector and any equipment running to it. (Ie... laptop, DVD player, etc...)

As a word of caution, DO NOT use anything that actually lifts the electrical ground from the equipment. Don't use a 3 prong to 2 prong adapter or any such thing. You could be asking for trouble IF something were to go bad and someone were to accidentally receive a shock.

At Wal-Mart, they sell the Scocshe brand for $15.00 in the car audio section. http://www.walmart.com/catalog/produ...duct_id=896355

At RadioShack, they sell their own brand for $16.99. http://www.radioshack.com/product/in...ductId=2062214

You should be able to pick these up locally and they work.

Just my 2 cents worth...

Chris

[BC-Short]

We had a hum when we recently added a computer for recording. We are taking sound directly off of the mixer and sending it to the sound card on the computer. Unknowingly we had mixed stereo and mono cords/plugs. The unused half of one of the stereo connectors allowed the 60mhz hum to get into the system.
We got a plug designed for mono to stereo (1/4' to 1/8" adapter) and that took care of the problem.
Ground loops can be really hard to diagnose.

[chazman14]

I noticed a hum in my church's system when we installed a new computer for projection. We also use that computer to record the sermon and play cd's/music. Should I get a ground loop isolator for both the input and the output of the computer? Thanks.

[gletiecq]

One item I've found extremely useful is the EBTech Hum-X. Runs about $70 at B&H and elsewhere, and you plug it into the outlet and then plug your audio gear's power cord into that. It seems to safely do a ground lift, and I've used it on several occasions when different gear was on different circuits.

There's also make a sweet looking stereo isolation transformer from ART with XLR, RCA and 1/4" jacks that I bet would work for a video signal in a pinch, as well as audio. I haven't played with it yet, but it's my next utility gear buy when money is available. If anyone has experience with this one, let us know.

If you've got to move stuff around or be mobile, some sort of ground isolation gear is absolutely necessary as you'll run into this problem time and time again. Nice to have the tools to fix these problems when they pop up, because they can destroy your sound or video quality.