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Loud humming through amp when USB is attached.
by randyNH on 2009-09-24 02:18:23

  I am not sure if it is possible to have audio playback through the amp when the USB is attached, but I get a loud humming.  The way that I have the amp setup is I have the 2 outputs to the effects return line.



Re: Loud humming through amp when USB is attached.
by silverhead on 2009-09-24 07:13:29

That seems to be a common problem and I'm not sure there's a simple answer. Many people report different levels of signal noise that seems to be introduced by the USB connection. In some cases it's present but not too annoying and in other cases it's unacceptable. Seems to depend on the amp, the X3 Tones (hi-gain?), the cables, the electrical outlets, etc, etc, etc. Best advice I can give is to experiment to see if you can minimize the noise. I think it's unlikely that you can remove it altogether, but likely others have more insight into this.



Re: Loud humming through amp when USB is attached.
by knobsmcgee on 2009-09-24 08:35:58

I have the same problem, kind of a mix of hum and digital noise. I think it's some kind of ground loop issue related to my laptop.  I don't have to plug the cable in, just touch the outer ground shell of the USB cable to the ground connection of the computors USB port and BZZZZZZZZZ.  I had the same noise when connecting the headphone output from the laptop to the board in my studio.  I inserted an Ebtech ground isolator/impedance shifter and it went away.  Unfortunately I've never seen a ground isolator for USB.

Watcha gonna do?

Knobs



Re: Loud humming through amp when USB is attached.
by TheRealZap on 2009-09-24 09:51:54

you can get better shielded USB cables... even monster cable makes them... no guarantees... just saying its an option.



Re: Loud humming through amp when USB is attached.
by knobsmcgee on 2009-09-24 12:04:44

I don't think it's the type of hum that better shielding would cure (even Monster's magic voodoo sheilding).  If so, the hum would be there even with it disconnected at the computer end.  With mine, the noise goes away as soon as I unplug from the laptop.

Knobs



Re: Loud humming through amp when USB is attached.
by TheRealZap on 2009-09-24 12:18:34

what that likely is... is noise generated by the motors in your fan and hard drive... cables could possibly help.



Re: Loud humming through amp when USB is attached.
by Data on 2009-09-24 12:24:50

I have that problem in my setup with an XTLive and my laptop.  I found that by plugging everything into the same power strip and adding a ground wire from the Pod to the outlet strip reduced the noise substantially.

The other costlier solution is to get a fiber optic isolated USB.  They cost about $200 but it will definitely break the ground loop between the Pod and the laptop.

Data



Re: Loud humming through amp when USB is attached.
by knobsmcgee on 2009-09-24 14:01:54

Until I downloaded Guitarport to try out, it wasn't much of an issue as I just used Gearbox for back-up and some editing.  Since the noise level stays constant reguardless of the output level (the other reason I think it's a ground loop) as long as I send a good hot level from the X3 and trim it back going into the board, it's not too bad.  Maybe I'll try a better USB cable just to rule that out.

Knobs



Re: Loud humming through amp when USB is attached.
by Nick_Mattocks on 2009-09-24 14:28:14

It's a ground loop issue.  If you run your laptop on batteries the noise stops?  Your laptop's PSU (probably) has a three core (inc ground wire) mains cable.  You need a PSU that doesn't require a ground wire - i.e one with a two core mains input.  You should not disconnect the ground wire in your laptop PSU's plug on safety grounds, but should source an alternative PSU for your laptop with a two pin mains input.



Re: Loud humming through amp when USB is attached.
by timowens on 2009-09-24 19:21:47

Yes, it is a ground loop problem. You can also use a direct box (DI) with a ground lift or a hum eliminator to help fix this.



Re: Loud humming through amp when USB is attached.
by randyNH on 2009-09-25 02:02:07

So I would connect the DI box between the POD and the amp?



Re: Loud humming through amp when USB is attached.
by Nick_Mattocks on 2009-09-25 05:31:01

Using a DI box should kill the hum at the amp if that was the source of the ground loop - but I think you'll find the loop exists between the X3 Live and laptop's PSU.  that's what happened here until I swapped the laptop PSU.  The problem exists (on my systems at least) when just the X3L is connected to a laptop (or desktop PC) that is earthed - so getting the right type of PSU (without third ground wire) for the laptop is recommended.  Disconnecting the earth wire from the laptop PSU at the plug end would have the same effect in terms of removing the buzz, but is NOT recommended on safety grounds - and on your own head be it if you do try this.  Fortunately I have two different laptops that both supply 19v DC and one has a three wire mains lead whilst the other has a two wire mains lead without the ground wire, so I can use either PSU



Re: Loud humming through amp when USB is attached.
by timowens on 2009-09-25 06:40:24

Yes, I used a DI (with a GND lift) between my X3L and my JBL EON and it worked for me, I've read where others have used the HumEliminator and that worked for them.



Re: Loud humming through amp when USB is attached.
by Jay_A on 2009-09-29 14:33:19

Ebtech makes a Hum X Voltage Hum Filter that will solve the problem for you. Cheap fix that gets rid of the hum. http://www.americanmusical.com/Item--i-EBT-HUMX-LIST



Re: Loud humming through amp when USB is attached.
by knobsmcgee on 2009-09-29 15:19:39

I hooked up an Ebtech between the POD and mixer last night.  It didn't do away with the noise completely but it reduced it by a good 10db-12db.  It's definitely a ground loop issue!

Thanks for the "input",

Knobs



Re: Loud humming through amp when USB is attached.
by Jay_A on 2009-09-29 18:35:02

You may still want to try the Hum X Voltage Hum Filter. It plugs into a power outlet and then your laptop would plug into that. Since it is the transformer on your laptop that is causing the issue, it makes sense to eliminate the hum there. You also are not running your signal through a filter so it has absolutely no effect on your tone. That is a major plus. I carry a couple of these in my gig bag because you never know what the electrical system might be like in some places you play. I am not to keen about lifting the ground on things.



Re: Loud humming through amp when USB is attached.
by knobsmcgee on 2009-09-30 08:09:14

I've seen those in catalogs and such but never paid much attention.  I've got three of Ebtech's impedence shifters that I use for non-critical audio and have been impressed by the transparency for the price.  Do you notice any voltage loss through the Hum X?

Knobs



Re: Loud humming through amp when USB is attached.
by Jay_A on 2009-09-30 09:41:56

I have not noticed any voltage loss. I have also taken a multimeter and tested the voltage of the outlet without the hum x and then through the hum x and they were the same. I also tested my laptop powersupply at the tip with and without the hum x in place and no drop.

A cheap work around might be to plug you laptop into a different outlet not on the same breaker. Run an extension cord from a different room and plug your laptop into that. Probably will not get rid of it but will most likely reduce it some.



Re: Loud humming through amp when USB is attached.
by waveformer on 2009-10-07 19:10:40

You may want to try USB isolator, it's sure way to cut the ground loop. Analog Devices recently announced ADuM4160 chip; inexpensive devices based on this IC should already be available.



Re: Loud humming through amp when USB is attached.
by Jay_A on 2009-10-07 19:23:25

A USB Isolator works as a hub. The x3 does not work through hubs due to the bandwidth needed. It would also not get rid of any ground loop if you were to need to use the headphone jack to send sound to a board for instance. For USB connections they work fine. There are better options for getting rid of ground loops.



Re: Loud humming through amp when USB is attached.
by randyNH on 2009-10-08 01:44:15

  So I unplugged the power source of my computer ( I have a laptop) and the hum is gone.  Now the only problem is I don't hear any playback from the computer when I attempt to play back something I recorded.  I am confused I can here it through the headphones, but it doesn't transmit to the amp.



Re: Loud humming through amp when USB is attached.
by Jay_A on 2009-10-08 07:04:27

When you plug something into the headphone jack, it bypasses the 1/4 inch out jacks.



Re: Loud humming through amp when USB is attached.
by randyNH on 2009-10-11 18:13:13

  I usually leave my headphones attached at all times even when I play through the amp.  I disconnect the headphones and I still cannot get sound through the amp.



Re: Loud humming through amp when USB is attached.
by randyNH on 2009-10-13 16:25:44

anyone else have this problem?



Re: Loud humming through amp when USB is attached.
by TheRealZap on 2009-10-13 16:40:11

doesn't work that way on mine... headphones and 1/4" active all the time



Re: Loud humming through amp when USB is attached.
by TheRealZap on 2009-10-13 16:40:58

possibly you have the outputs muted... but i've never heard of this one.



Re: Loud humming through amp when USB is attached.
by Jay_A on 2009-10-13 19:03:05

That is not normal at all, You might want to have that thing looked at. Or at the least, try doing a system reset and see if it fixes it.



Re: Loud humming through amp when USB is attached.
by bjanders on 2009-11-16 14:38:06

Just wanted to report that I am also experiencing the humming problem. I can experience it even without a computer attached, or anything else connected to a power supply. I have reduced the setup to the following:

- Connect a cable between the output of my M-Audio ProFire 610 and the guitar input (or aux input) of my X3

- The ProFire is not connected to anything else. No power cable, no firewire, no nothing. Not that it matters, but the power switch is also turned off.

- At this point there is no hum

- Touch the grounding of a firewire cable connected to the ProFire and the grounding of a USB cable connected to the X3. Now a clear, not very loud, but annoying enough, hum is heard.

Note that the only thing connected to a power outlet is the X3.

Disabling the input where the audio cable is attached (guitar/aux) removes the hum.

I'd be happy to find a solution to this humming problem (without spending a lot of money).

Message was edited by bjanders: Changed "this problem" to "the humming problem", so that is not confused with the other problems discussed in this thread.



Re: Loud humming through amp when USB is attached.
by Schinto on 2013-01-12 13:12:02

I have a very similar problem.  I don't have a lap top, but a desk top Mac.  The noise goes away as soon as I disconnect the POD from the USB cable.




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