PC causes house speakers to always buzz?

MrPockets

Gold Member
The PC that runs the slideshow makes speakers buzz during playing.

The PC must be on during playing.

What should be troubleshot?
 

dboomer

Senior Member
Is it a laptop? Either way ... run it on batteries or put audio through a transformer style DI
 

Smoke

Silver Member
Sometimes it's a common ground problem. You can check easily with a 3 prong to 2 prong adapter - probably have one on an extension cord already or in a toolbox. I'd try isolating the PC first.
 

trickg

Silver Member
Sometimes it's a common ground problem. You can check easily with a 3 prong to 2 prong adapter - probably have one on an extension cord already or in a toolbox. I'd try isolating the PC first.
+1 - that's the same thing I was thinking.
 

Smoke

Silver Member
87157One of these guys will do the trick to isolate your PC. Probably $2 USD or so for a pair. I've usually got a couple around the house/garage for old tools and electrical outlets. We get the same problem measuring thermocouple (very low) voltages when logging the data on a laptop. My guess is that the PC fan motor might be back-bleeding into the PCs ground which is (probably) common to the whole system. Just enough noise in the ground to cause buzz in the speakers, but not noticeable anywhere else. Isolating the PCs ground will give you a clue, and for 2 bucks, it's cheap troubleshooting. Let us know what you find.
 
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GruntersDad

Administrator - Mayor
Staff member
I had this issue with a small mixer and was told by the manufacturer to plug the PC and the Mixer into seperate electrical outlet lines. Everything i recorded had a buzz.
 

Smoke

Silver Member
I had this issue with a small mixer and was told by the manufacturer to plug the PC and the Mixer into separate electrical outlet lines. Everything i recorded had a buzz.
Did it work? Typically there's only one ground point in a house, but many paths to get there, depending on the circuit design. As long as you didn't use the same electrical outlet, ;-) it might have mitigated the problem. Most times at work, we're working off a 6 foot long power strip on a bench, so no matter where you plug in, if somebody's injecting noise on the ground, everybody on that power strip gets it. Thankfully, it's not really noticeable for most measurements - but when you're measuring microvolts, it can cause havoc.

We call the 3 to 2 prong adapters "ground busters." It doesn't solve every noise problem, but it's the first quick and easy check.
 

Smoke

Silver Member
87158Forgot - at a gig, you're stuck with whatever power the host/venue makes available, so extension cords and outlet multipliers are probably the order of the day. For $10 to $20 USD, a few ground busters and couple multipliers are cheap insurance at the bottom of a gig tool bag with your extension cords. If the ground buster doesn't work with the PC first, it's quick and easy to move to other power cords.

(I was going to remind folks not to overload power cords and multipliers, as that could be a fire hazard. If you burn down your client's venue, you may not get called back! But, figured they already knew that, so didn't...)
 
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