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Low pitch hum: mixer or wires?

I just bought a Behringer DJX400. I know it's not the best, but I just wanted it to fool around at my house. Anyway... There's a low pitch hum that comes over the speakers that goes up and down the same as the volume. Is it the mixer or the RCAs(they're just regular RCAs)? Thanx for any help.

Craig

The set up isn�t grounded properly! Make sure the ground wires from the turntables are plugged into the ground of the mixer.

I use my laptop as the source. I bought better wires today that go from the mixer to the receiver. So hopefully that will fix it.

yea make sure your wires are shielded and that you have the ground wires connected correctly

If you are using your laptop as the source, it could also simply be your sound card. I know that one of my sound cards in my PC, my older SB Live! makes some funny backround hum. This tends to happen with many sound cards. Don't know how to fix it though...

quote:

Originally posted by Hyoctane I use my laptop as the source. I bought better wires today that go from the mixer to the receiver. So hopefully that will fix it.

Ah right, you should have said what your source was! I used to have this problem with an old Sound Blaster sound card I had ages ago. Basically there is a short running through the system because the output port of the sound card is kiaboshed. I discovered through wiggling the connection that in certain points it wouldn�t feedback, so just rigged it to stay there!

I also found two little adjustable copper knobs, one over each set of inputs that say GRND. Those are the ground for the inputs, but how do you ground them?

Craig

Also, does your laptop have a 3 prong power connector or two? Laptops that use the 3rd grounding prong generate alot of noise if the mixer is hooked up to the same circuit. I would begin disconecting components and see if you can find the source of the problem.

Yes, it does have a three prong connector for the power. Which components are you talking about disconnecting? Can I ground the mixer externally?

Craig

quote:

Originally posted by Hyoctane I also found two little adjustable copper knobs, one over each set of inputs that say GRND. Those are the ground for the inputs, but how do you ground them? Craig

They are the ground lugs for the turntables, the mixer is already grounded. You don�t need to connect anything to these except when you�ve got some vinyl players!

quote:

Originally posted by Hyoctane Yes, it does have a three prong connector for the power. Which components are you talking about disconnecting? Can I ground the mixer externally? Craig

When laptops use a 3 prong plug, the third prong grounds the laptop's chassis. The chassis on laptops are very close to the cpu and other components, so it transmits lots of rf interference and when your mixer and turntables are on the same line that would transmit noise into your mixer.

I would start by disconecting your laptop and any other computers/tvs that are on the same circuit in the house. If that doesn't do it, just have the mixer pluged in by itself w/o anything attached, then start plugging in gear until you hear ground loops. (the device that creates the noise will be the culperate)

This is a really good guide that rane shipped w/ my empath, and when correctly followed worked wonders:

http://www.rane.com/note110.html

Oh yeah, i forgot to add this: I experienced the same problems w/ my laptop especially at gigs, so i ran off to the home depot and bought a 3 prong to 2 prong plug adapter. Now that my laptop is not grounded, i don't get as much noise.

That should help

ya its a ground loop

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