Electrical interference on laptop recordings

Richard Durrer · Post by **Richard Durrer** » 9 May 2009 5:34 pm

I am currently using a Dell laptop and Reaper to record sermons at our Cowboy Church. I feed a stereo 1/4 inch signal from the board mains to a headphone amp, then out to the laptop. I have noticed lately that I am getting a high pitched whistle on my recordings now. I can also hear it in the wireless headphones. The whistle disappears when I unplug the laptop from the power plug. The brick is still plugged in though. Someone from a sound forum suggested I run the signal thru a DI box to isolate the interference. However it does not make much difference. The interference is still noticable. Any suggestions?

Andy Sandoval · Post by **Andy Sandoval** » 9 May 2009 6:05 pm

Have you tried a ground lifter (three prong to two prong adaptor) on the laptop power supply cord? I had a similar problem with my laptop and it worked for me.

Richard Durrer · Post by **Richard Durrer** » 9 May 2009 7:15 pm

I have not tried the two prong adapter. Am I not putting myself at risk by doing this? There have been several topics suggesting that this approach may be dangerous.

Andy Sandoval · Post by **Andy Sandoval** » 9 May 2009 7:29 pm

Well, you can't live forever. Just kiddin,

be sure and post how you remedy the problem.

Ken Metcalf · Post by **Ken Metcalf** » 10 May 2009 7:26 am

I had the same/similar prob.
Went down to Guitar Center Music store with my lap top and tried expensive power conditioners etc.
the only one that worked was a Hum-X that goes on the 110V power plug.

Bent Romnes · Post by **Bent Romnes** » 10 May 2009 10:20 am

Rich, I hope you get to try what we discussed on Skype last night. Let us know the results here. It would be interesting to find out about this.

Karlis Abolins · Post by **Karlis Abolins** » 11 May 2009 6:13 am

Richard,

Your best solution to this issue may be to use an old desktop pc that you can leave in the church for this purpose. I spent a couple of years chasing this problem and ended up giving the laptop to my wife and buying a small pc that I dedicate to music. No more interference.

Karlis

Richard Durrer · Post by **Richard Durrer** » 11 May 2009 6:55 am

Thanks to all for your comments. I can't use a desktop since I update our website with the recordings on the laptop. The church space is actually a large rented convention centre and we tear down every night. All the equipment has to fit into several large cabinets. I use a Peavey 32FX board that has a USB output. I am going to try that option into Reaper on Tuesday night. I will post the results. Rich.

John Roche · Post by **John Roche** » 14 May 2009 3:22 am

Here is a program that will stop all noise on your computer, $30 for the full version, down a trial version free, I have been using it for a few years now
great program..
http://www.softpedia.com/get/Multimedia ... oise.shtml

David Collins · Post by **David Collins** » 16 May 2009 12:24 pm

Richard, went through the same thing with my dell. It is as simple as lifting the ground prong on the power plug. A simple 3 prong to two prong adapter from any hardware store or department store will do the trick.

Did on mine. Keep it in the bag with the laptop at all times!

winston · Post by **winston** » 17 May 2009 7:48 am

Light dimmers cause noise problems in sound equipment. I agree with andy and david, use a ground lift connector for 30 cents and it will solve your problem. I would recommend using the adaptors on all you sound equipment and your computer. The late Jeff Newman taught me that trick. He said that years ago at the Opry that is what they did to eliminate ac noise from the amps. I have been using them for years and have never had a problem. winston may

Jon Moen · Post by **Jon Moen** » 17 May 2009 8:49 am

It would be safer to leave the power ground as it is intended, and put a ground lift on the audio cable.

John Roche · Post by **John Roche** » 18 May 2009 3:57 am

Has anyone tried the program I posted yet?

Richard Durrer · Post by **Richard Durrer** » 18 May 2009 9:28 am

Hi Folks. Since I only have access to the sound system on Tuesdays, for a limited time before showtime, I have not tried the software solution. I did try the USB connection to the mixer, but could not get any sound thru to the mixer. Reaper did recognize the Peavey mixer, and I chose that setting but no go. I did not change the setting within Windows. That was probably my mistake. I will attempt it again tomorrow (Tuesday). I may opt for the Behringer Hum destroyer with the integral ground lift etc. (Behringer HD400-2 Channel Hum Destroyer - HD400 $38.99 CDN). Rich.

John Roche · Post by **John Roche** » 18 May 2009 9:40 am

a screenshot of no noise.

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Kevin Rose · Post by **Kevin Rose** » 18 May 2009 11:52 am

Finding the source of the noise and eliminating it is always preferable to using software. I do a lot of location work, ground lifts, transformer isolation and all manner of tricks come into the game. I do know a lot of laptops have PSU issues and require ground lifting or some sort of isolation between console and input.

The problem may also be impedance related.

So hard to tell from here.

Bill Terry · Post by **Bill Terry** » 18 May 2009 12:59 pm

Richard,
Our church uses the same Peavey mixer with the USB port. We just record the service to a USB memory stick and then transfer the result MP3 to a computer for editing, trimming or whatever. Ultimately it ends up as a webcast on the webpage I think..

Are you turning on the 'USB record' feature at the Peavey Mixer? It's under the Util menu if I remember correctly. This works well for us, although to my ears the MP3 audio is a bit colored.

Richard Durrer · Post by **Richard Durrer** » 21 May 2009 8:28 am

Well- here's an update re: the "noise". I have tried the USB from the Peavey mixer again. Everything was connected and installed correctly on the laptop. The record light was lighted in the on position on the board: still no sound at the laptop. It appears I have may have to do a firmware upgrade on the board. I did install the software progam "No noise" and noticed no difference.

Now, to back up a moment, originally the Dell had a two prong plug from the power supply. When the power supply failed I replaced it with a 3 prong Dell power pack. That is when the problem first appeared. I have since replaced that power pack with another, also a 3 prong plug. VOILA. The recording is now quiet again.

So, I will leave it alone for awhile and keep monitoring the situation. Thanks to all for your suggestions. Rich.

John Roche · Post by **John Roche** » 21 May 2009 11:37 am

[quote]I did install the software progam "No noise" and noticed no difference.

Did you turn it on?

Richard Durrer · Post by **Richard Durrer** » 21 May 2009 11:59 am

John: Yes, I absolutely turned it on. I checked the sound before and after: no difference.

In addition, I checked for noise with the new power pack plugged into the laptop. Then with the power unplugged from the laptop. Then with the power unplugged from the AC source. It all sounded the same thru the wireless headphones. Then at home I checked what was recorded. There was no hiss, etc, like I had before. I concluded it must be the new power pack that solved it.