DJGold

jbrown157 · Posted: Mon Apr 17, 2006 5:43 am Post subject: RF from power supply?

I took my newly assembled ceremony system out to do a small reception held in a restaurant. Everything worked fine at home but I had a buzz through the system while at the restaurant. The noise stopped when I disconnected the power supply from the laptop. I've ordered a power conditioner to install in this system - hopefully, this will filter out the noise in the future. I'm thinking that I had dirty power at the restaurant. Any ideas?

dokai · Posted: Mon Apr 17, 2006 7:15 am Post subject:

I've run into a similar problem and it turned out to be the laptop's power supply. I replaced it with an identical one, and the hum/buzz disappeared. This is after the noisy power supply had worked fine for over a year, and STILL powered the laptop with no problem - it was just noisy when connected to my DJ system. Yet replacing it caused the problem to vanish, and putting it back in caused the problem to reappear, so there's no doubt that it was the culprit.

A power conditioner is still a good investment, but you may want to try a replacement wall-wart, too.

jbrown157 · Posted: Tue Apr 18, 2006 7:23 pm Post subject: Re: RF from power supply?

This was a second power supply that I purchased so I'd have a backup. Upon closer examination, I noted that the "new" one had a three prong connector - the original one didn't. Plugged the original one back in---no buzz. Problem solved (I hope). Thanks (again) for your help!

dokai · Posted: Tue Apr 18, 2006 7:58 pm Post subject:

LOL! An evil wall-wart strikes again! :hahaha: Glad it was an easy and cheap fix.

If it's difficult to find a two-prong version to replace it, you could try using a three-prong-to-two-prong AC adapter on the noisy power supply. That MAY help.

TheBartman47 · Posted: Wed Apr 19, 2006 9:08 am Post subject:

This is actually a very common problem with laptops. Also, a power conditioner won't help. The only solution I've ever found for laptop noise is using the AC ground adapter. *Note, this is the ONLY time I would ever use an AC ground adapter, never on amps or mixer or other sound gear that anyone might touch while plugged in.*

len · Joined: July 2nd, 2005 Posts: 105

You might also get an active DI. The ground lift worked for me but sometimes the DI was necessary as well.

TheBartman47 · Posted: Thu Apr 20, 2006 11:27 am Post subject:

I have a Dell laptop, and I can turn the volume up with nothing playing, and still hear the noise from the power supply through the laptop's littel built-in speakers, so the issue isn't a ground-loop problem (for Dell computers at least) between the laptop and mixer. It's just noise injected from the AC adapter. Most likely a design flaw in their power supply. I have also used an HP laptop connected to my mixer with absolutely no noise problems at all, even with it's AC adapter plugged in with ground pin and all.

jbrown157 · Posted: Thu Apr 20, 2006 2:17 pm Post subject:

len wrote: You might also get an active DI. The ground lift worked for me but sometimes the DI was necessary as well.

Pardon my ignorance... but what's an active DI?

TheBartman47 · Posted: Fri Apr 21, 2006 9:39 am Post subject:

Active DI (Direct Interface) box is one with a pre-amp circuit, and therefore requires power to operate (batteries usually), as opposed to a common "passive" DI box, which is simply a transformer to change the voltages from line level outputs down to microphone levels so you can plug a device into an XLR mic jack on your mixer. These DI boxes usually include a ground lift switch to eliminate a ground loop problem between your mixer and the device you want to connect.