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I bought a couple of Behringer b3031a monitors for my digital piano. Hooked it all up (they sound great, by the way...I recommend them) but I get a high-pitched buzz that's annoying me.

I was afraid it was the monitors' fault, so I unplugged the audio cables and the buzz disappeared. The monitors seem fine. If I unplug the USB cable that connects my external interface to my computer, the buzz goes away. If I power down the computer, the buzz goes away.

So I thought "maybe this is what a ground loop is." So I plugged the monitors into another outlet. Now I got a low-pitched hum in addition to the high pitched hum. Ok, that was the wrong way moved it back. Now I'm back to the high pitched buzz, only when the computer is on and the external interface is connected and running is there a buzz.

Is this a ground loop, or perhaps interference of some kind? My external interface never caused a buzz with my last set of speakers. Nor is there a buzz through headphones attached to the interface.

Specifics:

* Monitors, DP, and computer all plugged in to the same power bar.

* External interface is Behringer uca202 attached to computer through USB. It has no power supply of its own.

* The connection between my interface and the monitors is unbalanced (rca to ts).

Any idea what is going on? Do I need to get a new interface that has balanced outputs, or do some electrical thing associated with grounding? I think there's a screw on my interface that you can connect to a wire and run to a ground. Would that help? What tests can I run to determine where the problem is?

Sorry to be ignorant. This side of electronics is not my strong point.

How about trying a 'hum destroyer'?

http://www.amazon.com/Behringer-HD400-2-Channel-Hum-Destroyer/dp/B000KUD2G4

Cheers,
James
x

Consider yourself lucky that it's only a buzz. Those Behringers are known to function as radio receivers. If you live near a strong radio station, the Behringer's will play that station, even with no speaker cables attached!

So just how high is that high-pitched buzz? It's probably coming from a computer, though it could be from a switch-mode power supply in any so-equipped device.

Is this computer a laptop? If so, try unplugging the power supply/charge and run on batteries. (The charger is a switch-mode power supply.) Does that make the buzz go away?

Turn off the piano, but leave the computer and speakers turned on. Does it still buzz?

Good suggestion. I need to make sure AC hum is the source of the problem, though. If something is picking up rf interference this wouldn't help, right?

I'm not sure - I've actually never used one.

However I know it's something the Kawai Europe chaps recommend when customers (connecting their DPs to a laptop/desktop using USB MIDI) complain of signal noise/hum.

Cheers,
James
x

The computer is a desktop.

When I turn off the piano but leave the computer on the buzz persists.

It's pretty high pitched. I think it's the same pitch as the highest B on the piano or an octave below that. It's not regular, it sort of comes in and out a little.

By the way, as the computer turns on and boots up there's no buzz. It's only when windows fully boots up and actually loads the driver for the interface that the buzzing begins.

BTW I haven't actually connected my digital piano directly to the monitors without going through the computer yet. I should try that (just need to dig through some boxes to find the right cable).

Edit: actually I don't own a 1/4 trs to trs cable nor xlr cables. It will be a while before I can test the piano running directly into the monitors.

Here is a suggestion similar to James's suggestion. Only you plug your computer's power cord into this.

Hum-x
http://www.amazon.com/gp/product/B0002E4YI8/ref=ox_sc_act_title_7?ie=UTF8&m=ATVPDKIKX0DER

Personally, I'd rather go this route than the hum destroyer. I'd be concerned about the humdestoyer effecting sound quality, whereas the Hum-x takes care of the ground loop at the source (the ac outlet). It's safe, your equipment is still grounded when using the device. Based on reviews, it sounds like it works for most people with a genuine ground loop problem.

The OP says this is a high-pitched whine. It's the computer/soundcard, not the power source.

That's kind of what I thought. I think I have one of those plugs that disables the ground. If I plug the whole system in through that (so that nothing is grounded) and the noise persists, then it means it's not a ground loop, right?

EDIT: tried it. Hum persists even when nothing is plugged into a ground. Does the mean it's not a ground loop thing?

It still could be a ground loop. Remember that the power plugs are not the only interconnections here. There are cables running from piano to PC, and from PC to the UCA202, and from the UCA202 to the monitors. Any one of those can cause ground loop problems.

Still, I don't think this is a ground loop. Instead, I think the noise is coming from either the PC or from the sound card.

Unplug the UCA202 (both sides). Then connect the monitors to the PC's internal sound card. Since you have a desktop, that card likely has a line output just for this purpose. Does that eliminate the noise?

I'll give it a shot. I actually have the oboard sounds disabled in the BIOS, but I'll re-enable it. If that does stop the hum, does that mean I need to replace the UCA202 or somehow ground it to the computer?

By the way, if it's a ground loop, would using XLR connections help (moot anyway because the UCA202 does not have balanced outputs)?

Yes, my soundcard has balanced (XLR) outputs, and it solved a noise problem for me when I switched to balanced connections to the monitors. It's one reason to spend the extra on a soundcard & monitors with balanced connections.

Another idea I saw somewhere in here was to insulate ONE end of the USB cable. Tape around the metal sheath of the connector. This solved the problem for that user.

Greg.

Well I just learned a lot.

I moved the USB connection to a different USB port and the hissing stopped! This apparently is because the driver actually cares which port you are plugged into and once I moved it, it couldn't find the device (amazing, but I already knew this). So I wasn't able to use it to play the piano. I reinstalled the driver--as I have in the past to fix that problem--and when it took effect, the hiss started again, without any hardware changes.

Further, there's a kind of scratching sound that is intermittent. Without the hiss it was clear what it was. Whenever the hard drive seeks, there's a scratching sound. Whenever I move a window on the screen, there's a buzz at a different frequency. When I move the mouse sometimes there's a scratch. When I unplugged the USB cable and touched metal (the usb sleeve) to metal (the computer case) I got a scratching too. I'm beginning to think that insulating the USB termination sleeve might be the right answer.

There's a screw on the UCA202 that has the sign for "ground" next to it. I could attach a wire to it, but what would be the right thing to ground it to in order to stop getting all these computer effects?

By the way, it's actually a UFO202. I stuck with UCA because they are almost identical and the UCA is more common, but now I see that there is no ground thing on the UCA...maybe that's just a vinyl recording thing.

Maybe you will learn why few people will recommend anything made by Behringer. Hum, buzz and hiss pretty much comes with the brand name. But you might be able to minimize the noise

Here are some ideas......

1) USB bus powered interfaces sometimes are a problem. There ground reference is the USB cable shield. So yes perhaps a ground strap that connects the interface to the PC chassis. Make it bare metal to bare metal. Remember that all aluminum is coated with an insulating layer of oxide so use a star washer that cuts in. Use a good size wire too. Also if you can, try powering the USB box with a plug-in power cube

2) Yes if you have the option balanced interconnects will pick up a lot less noise. But before that make sure you are using QUALITY un-balanced cable. Not stacks of adaptors and good braided coaxial cable. Keep the cable short as you can and not bundled with other cables.

3) Farite beads can help if the problem is picking up radio. You computer can be a good source of "radio noise". Places like Radio Shack might sell the beads but I salvage them when I can and keep some in my parts bin. They look like "bumps" in a cable

4) You best option is to break down and spend the $$ for pro quality gear that uses balanced interconnects and then use quality balanced cables with either XLR or TRS plugs

5) I don't know what USB audio interface you have but a low-end bus powered one might might have a higher output impedance than you'd like. This would make the cable susceptible to noise. An easy work around might be to always run the computer volume at 100% and then lower the vole with the analog control that should be on the speaker. Basically you are trying to over peer the noise with more signal.

The way a ground loop works is some how there is current in a ground connection. By ohm's law if there is current there is also a voltage drop. A voltage drop in a ground connection means that there are two places that you think of as "ground" but if there is a drop then they can't be the same zero volts.

Of those five options, only #4 is possible here. The others just won't work with the given Behringer device.

I'm not seeing anyone recommending a ground loop isolator. Not a solution in this case? Do they degrade the sound quality?

Regarding #1 I don't see a way to plug it in to its own power (it runs off of USB power), but I certainly could run a cable from there to the chasis. Would that not work, MacMacMac?

By the way the speakers are at minimum physical volume. When I increase it the hiss increases. Changing the volume on the computer does not affect the hiss one way or the other.

The ground loop isolator on the power cord likely won't do any good because I don't think that's where the problem lies.

1. Do you have another computer? Can you try this on that other computer?
2. Have you tried the tape around the USB connector? I'm skeptical, but it costs nothing to try.
3. Can you try the computer's internal sound card?
4. Can you get a better sound card, instead of the Behringer?

I really think you'll need a different sound card (item #4). Why? Because you said earlier:
I moved to a different USB port and the hissing stopped! The driver actually cares which port you plug into. Once I moved it, it couldn't find the device. I reinstalled the driver. When it took effect, the hiss started again.

So the fault is probably with the sound card. Chris has said (as have many other people) ... you don't buy Behringer. Their stuff is bottom-of-the-line. Sorry for the bad news, but that's the way it is.

Hi MacMacMac, the link I pointed to is a different type of isolator. It goes in the audio line, not in the power line. Apparently it allows signal but not current to go through the cable.

I did try the tape and unfortunately did not notice a difference.

I haven't tried the internal sound card yet. If I can't make the Behringer device work, I'll end up getting a higher end device. Probably presonus audiobox usb, focusrite scarlett, M-audio fast track pro, or tascam 144. But I'll make sure whichever I get has XLR outs and a decent headphone amp. I'd rather avoid this if possible (through the use of an isolator) though, obviously.

You won't need XLR outputs. Balanced lines help reduce noise PICK UP from external, radiating sources. In the home environment, that's not usually something you worry about. All your audio cables are shielded, so no worries.

In your case, the noise is coming from the sound card (or from the computer). Balanced lines won't help that. Not one bit. Still, many (most?) sound cards for music use have balanced outputs.

I'm using a Presonus AudioBox. Absolutely no troubles. It does have balanced outputs, but they're operating unbalanced because I plugged them into the unbalanced inputs of my amplifier. Fortunately, the box uses regular phone plugs, not XLR connectors, so it's easy to plug and play. And no noise at all.

Thanks MacMacMac.

Just to clarify: if I understand it right, the reason I'm getting hum is because my behringer USB sound interface is ghetto and allows current to pass where it shouldn't, not because there's something ghetto about my Behringer monitors?

That being the case, why didn't I notice this hum when the interface was connected to computer speakers? Computer speakers not sensitive enough?