Author Topic: US-20 Hum...?  (Read 4666 times)

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Offline musicman65

US-20 Hum...?
« on: February 26, 2011, 12:50:37 PM »
Guys,

anyone know why a US-20 would create a really loud hum when both VG99 and GR55 are attached. The hum is gone when only one device is connected. I have moved cables around, swapped ports, made sure power supplies are on the same ground, etc. The unit is used so I'm wondering if its bad?

Perhaps Elantric or any other hardware gurus can chime in with their expertise in the internal workings of the US20?

Thanks,

musicman65
« Last Edit: August 25, 2014, 11:39:32 AM by Elantric »

Offline 727lawrence

Re: US-20 Hum...?
« Reply #1 on: February 26, 2011, 01:39:39 PM »
I had a similar issue with two amps and wasn't smart enough to figure it out. I picked up an EBTECH Hum Eliminator and that did what it claimed to do - eliminate the hum. If one of the gurus on here can't figure this out for you then I would go that route.

Offline musicman65

Re: US-20 Hum...?
« Reply #2 on: February 26, 2011, 01:48:51 PM »
Thanks. Good advice on the Ebtech. I believe that would fix it but I'm perplexed why I'd need it when others don't in the same application. It's a ground loop issue, most likely. Neither device has a lift or polarity switch....so why me?

musicman65



Offline musicman65

Re: Re: US-20 Hum...?
« Reply #3 on: February 26, 2011, 08:40:37 PM »
bump!

so nobody else has a bad hum using a US-20 to interface to a VG99 and GR55 at the same time?

musicman65

Offline kenact

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Re: US-20 Hum...?
« Reply #4 on: February 27, 2011, 12:44:32 AM »
The most likely cause would be a grounding problem.  Can you provide more detail on your exact set up?
Godin Session Custom FTP, LGXT, LGX SA, Redline 1 PROTOTYPE, A12, A10, A4
Danoblaster Baritone w/GK-3
Gretsch Nashville, Viking
Fender Strats, Twin Reverb
Fret King Supermatic
Larrivee DV03RE
Seagull 12
VOX Phantom XII
Roland GR-55, 33, 30, 20, GI-20, RC-50, VP-7, US-20
and soon Sentient Six
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Offline djidoe

Re: US-20 Hum...?
« Reply #5 on: February 27, 2011, 08:09:11 PM »
Is USB connected to 1 of the 2 units ? That may be the problem...

Offline shawnb

Re: US-20 Hum...?
« Reply #6 on: February 27, 2011, 08:17:43 PM »
I have the same setup, US20=>VG99 & GR55.   No hum problem. 
« Last Edit: February 28, 2011, 11:13:17 AM by Elantric »
Address the process rather than the outcome.  Then, the outcome becomes more likely.   - Fripp

Offline musicman65

Re: US-20 Hum...?
« Reply #7 on: March 01, 2011, 01:07:33 PM »
Thanks ShawnB. I suspected others were using the US20 without issues.

As to the question of my exact setup:

RRStrat to US20 to VG99 and GR55. Both VG and GR are connected to my studio mixer with Left and Right 1/4" cables. No USB or MIDI to outboard gear. Both VG and GR power supplies are on the same power strip.

I am going to plug in Headphones to the VG and the GR directly while they are not connected to the mixer to see if the ground loop is in the audio circuit.

I'm leaning towards a bad US20. We'll see. Thanks to all who have responded.

Musicman65

 

Offline kenact

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Re: US-20 Hum...?
« Reply #8 on: March 01, 2011, 01:45:06 PM »
RRStrat to US20 to VG99 and GR55. Both VG and GR are connected to my studio mixer with Left and Right 1/4" cables. No USB or MIDI to outboard gear. Both VG and GR power supplies are on the same power strip.

If all your cables are grounded, you might try using a pair on one of the units with the grounds lifted, just to ensure there's no ground loop.
Godin Session Custom FTP, LGXT, LGX SA, Redline 1 PROTOTYPE, A12, A10, A4
Danoblaster Baritone w/GK-3
Gretsch Nashville, Viking
Fender Strats, Twin Reverb
Fret King Supermatic
Larrivee DV03RE
Seagull 12
VOX Phantom XII
Roland GR-55, 33, 30, 20, GI-20, RC-50, VP-7, US-20
and soon Sentient Six
MORE

Offline Elantric

Re: US-20 Hum...?
« Reply #9 on: March 01, 2011, 02:05:59 PM »
Quote
Both VG and GR are connected to my studio mixer with Left and Right 1/4" cables.

This might be the problem

If you have balanced 1/4" TRS inputs on your mixer,
Use the VG-99 XLR Sub outputs - these are  balanced

Use XLR female to 1/4" TRS balanced audio cables to connect your VG-99 to your mixer.

if hum persists, then Lift / float  the shield connection on these XLR female to 1/4" TRS balanced audio cables between the VG-99 Sub Outs to the Mixer Balanced Line inputs.

Offline Brent Flash

Re: US-20 Hum...?
« Reply #10 on: March 01, 2011, 02:07:09 PM »
You may know this already but just in case I would like to add some suggestions to this thread.

Ground loops can really be hard to figure out. Anything that is plugged into AC and then connected (audio cable, USB, MIDI, 13 pin cable, video cable, etc.) to another device that is plugged into AC has the potential to create a ground loop. And as other devices that are added to the connection that give potential ground paths increase the chances of getting a ground loop increase. It usually is caused by the device that you least suspect. Like USB or the mixer or something plugged into the mixer that is not part of your guitar rig.

One way to trouble shoot is to start unplugging audio cables, USB cables, while listening for the hum to go away. Also PFL channels on the mixer to see if it is coming in from one unit or both. For example just the VG or GR or both. Does you guitar have a GK3 and if so do you have the 1/4" cable from guitar out connected to the GK guitar in. Is there a guitar out of the VG connected to an amp?

If you have narrowed it down to the VG try an isolation transformer between the audio out and the mixer. Also if your VG is connected with XLR have you tried the ground lift on it.

If headphone outs are clean on both units more than likely it is the connection to the mixer. Use the XLR on the VG and run the GR into DIs that have ground lifts.

I guess it is possible that the US20 is defective but just because it starts when you use it does not mean that is the cause if you know what I mean?
Good luck in your quest. Let us know what you find.

Offline A2theT

Re: US-20 Hum...?
« Reply #11 on: May 03, 2011, 07:37:50 PM »
I still have a similar issue which I posted in another thread but mine is a light crackle.  Turning up noise gate on vg-99 resolves it but it is impeding the overall signal.
I wish I could solve this.  My setup is pretty basic.  VG-99, GR-55, US-20.  Both VG and GR outputs are sent to my Behringer Powered Keyboard Monitors.  If i disconnected the GR  1/4" outs or vg 1/4" outs the crackling stops.  Doesn't matter which one I disconnect but they both can't be going at the same time without crackle.  I have a balanced in on these speakers and have also tried that to no avail.  I also tried the ground lift switch on back of VG-99 but it still happens.  Wish I could solve this one.  I have replaced every possible cable. I even tried using the headphone outs of both vg and gr and sending them to my powered speakers but same result...  Must be a loop somewhere.  jeeshhhhhhhhh! ??? ??? ??? ??? ??? ???
HEAVY on the METAL
Axe-Fx II, Roland VG-99 + FC-300, Roland GR-55, Digitech Jamman Stereo, Ibanez/ESP/Jackson Guitars

Offline Brent Flash

Re: US-20 Hum...?
« Reply #12 on: May 03, 2011, 07:52:56 PM »
I still have a similar issue which I posted in another thread but mine is a light crackle.  Turning up noise gate on vg-99 resolves it but it is impeding the overall signal.
I wish I could solve this.  My setup is pretty basic.  VG-99, GR-55, US-20.  Both VG and GR outputs are sent to my Behringer Powered Keyboard Monitors.  If i disconnected the GR  1/4" outs or vg 1/4" outs the crackling stops.  Doesn't matter which one I disconnect but they both can't be going at the same time without crackle.  I have a balanced in on these speakers and have also tried that to no avail.  I also tried the ground lift switch on back of VG-99 but it still happens.  Wish I could solve this one.  I have replaced every possible cable. I even tried using the headphone outs of both vg and gr and sending them to my powered speakers but same result...  Must be a loop somewhere.  jeeshhhhhhhhh! ??? ??? ??? ??? ??? ???
Plug the VG's AC into same place the GR is plugged in or experiment where they are plugged in. It could be anything that is connected to AC and audio.

Offline Elantric

Re: US-20 Hum...?
« Reply #13 on: May 03, 2011, 11:29:00 PM »
Quote
Both VG and GR outputs are sent to my Behringer Powered Keyboard Monitors.  If i disconnected the GR  1/4" outs or vg 1/4" outs the crackling stops.


The noise you describe is caused by switching power supplies in all your gear, and a ground loop in the Audio path.
True  - no 60 Hz Hum is heard, instead you have pops and crackling - yes this noise is due to a ground loop.

Solve this problem by breaking the loop - by Inserting a Passive DI box (not active ) between the 1/4" Outputs of either the GR-55 or the VG-99 and the target  Behringer Powered Keyboard Monitors.


DO not use an Active DI box - these do not provide the galvanic isolation required to break the ground loop.
This works as a Passive DI box:

http://www.amazon.com/ART-Direct-Professional-Passive-Box/dp/B0009GYIL2
« Last Edit: May 04, 2011, 10:48:28 AM by Elantric »

Offline A2theT

Re: US-20 Hum...?
« Reply #14 on: May 04, 2011, 06:02:53 PM »
Plug the VG's AC into same place the GR is plugged in or experiment where they are plugged in. It could be anything that is connected to AC and audio.

Everything is plugged into my power conditioner.  I've now split everything into different outlets in my house but same issue.
HEAVY on the METAL
Axe-Fx II, Roland VG-99 + FC-300, Roland GR-55, Digitech Jamman Stereo, Ibanez/ESP/Jackson Guitars

Offline A2theT

Re: US-20 Hum...?
« Reply #15 on: May 04, 2011, 06:04:03 PM »

The noise you describe is caused by switching power supplies in all your gear, and a ground loop in the Audio path.
True  - no 60 Hz Hum is heard, instead you have pops and crackling - yes this noise is due to a ground loop.

Solve this problem by breaking the loop - by Inserting a Passive DI box (not active ) between the 1/4" Outputs of either the GR-55 or the VG-99 and the target  Behringer Powered Keyboard Monitors.


DO not use an Active DI box - these do not provide the galvanic isolation required to break the ground loop.
This works as a Passive DI box:

Thanks Elantric, will try this next.  In 25years of playing guitar and jamming and mics and PA's etc I've never experienced this..
HEAVY on the METAL
Axe-Fx II, Roland VG-99 + FC-300, Roland GR-55, Digitech Jamman Stereo, Ibanez/ESP/Jackson Guitars

Offline Brent Flash

Re: US-20 Hum...?
« Reply #16 on: May 04, 2011, 06:25:27 PM »
Everything is plugged into my power conditioner.  I've now split everything into different outlets in my house but same issue.
Those things can be hard to track down. I will never forget back in the analog days when we had racks of FX units and racks of Compressors/limiters/gates all hooked to a Yamaha 4K with insert cables and I had a ground loop. All the racks and the board were hooked to the same leg of the distro which should have given us a loop free setup. After lifting this ground and lifting that ground, nothing was working, I decided to plug the FX rack into the AC power condition in the Compressor/limiter/gate rack. The hum went away. So just for kicks I plugged the Compressor rack into the FX rack, hum was back. The only way it would work was the FX rack plugged into the Compressor rack. And this only happened at one venue in Galveston, Texas and no others.

Isolation transformers are usually the best fix, but sometimes there is no way to isolate the audio like in the situation I had in Galveston. I would have had to have about 24 of them to isolate all the inserts.

Good luck with it!

Offline Elantric

Re: US-20 Hum...?
« Reply #17 on: May 04, 2011, 06:41:07 PM »
Quote
Thanks Elantric, will try this next.  In 25years of playing guitar and jamming and mics and PA's etc I've never experienced this..


Switching power supply noise is a relatively new phenomena with unbalanced Guitar gear, due to the 2005 era EPA legislation mandating "Green" external power supplies must replace all inefficient DC linear power supplies.

Even pre 2005  Roland  / Boss ADA and PSA supplies (for Boss pedals )have been redesigned and replaced by new versions

http://www.bossus.com/gear/productdetails.php?ProductId=911&ParentId=253


More here:
http://en.wikipedia.org/wiki/Switched-mode_power_supply


http://www.energy.ca.gov/papers/2005-03-03_WILSON.PDF







 
« Last Edit: May 04, 2011, 06:49:53 PM by Elantric »

Offline A2theT

Re: US-20 Hum...?
« Reply #18 on: May 04, 2011, 07:47:55 PM »
I'm going to the store tomorrow to buy the ART DualZDirect box and see how that goes.  I was looking at the HumX by ebtech but man, $71 !
HEAVY on the METAL
Axe-Fx II, Roland VG-99 + FC-300, Roland GR-55, Digitech Jamman Stereo, Ibanez/ESP/Jackson Guitars

Offline Whip

Re: US-20 Hum...?
« Reply #19 on: May 10, 2011, 10:02:14 PM »
I had the same problem with noise and got the HumX. It got rid of my noise. I plug a power bar into it and run everything from it.

Whip
Roland VG-99 + FC-300,
Roland GR-55, US-20
SG,BC Rich, Lado, Strat, Godin, GK-2a's & GK-3, RMC
Bose L1 M2 & Compact's & T1's
Have Fernandes Sustainers on most guitars. They are a must  ;)

Offline Elantric

Re: US-20 Hum...?
« Reply #20 on: May 10, 2011, 11:14:47 PM »
Quote
I had the same problem with noise and got the HumX. It got rid of my noise. I plug a power bar into it and run everything from it.

Whip - thanks for the tip!

Offline Kevan

Re: US-20 Hum...?
« Reply #21 on: July 05, 2011, 12:24:21 PM »
For what it's worth. I had the same problem with my VG99 - VG8 - US20 setup and simply lifting the ground on the VG8 did the trick.

Offline A2theT

Re: US-20 Hum...?
« Reply #22 on: August 24, 2011, 11:41:59 AM »
So, I know I'm resurrecting an old thread but I thought I'd provide an update.  I purchased the ART Passive D/I only to discover that it still happens with no outputs connected except headphones. DOH!  I also purchased the Ebtech HumX (holy expensive!).
Anyway, none of it resolved my problem.  I tried ground lift which made a minor diff. I tried grounding the GR-55 directly to the earth ground on my electrical panel. No change.  So today I decided to make a video of my situation and during the video recording and troubleshooting demonstration I am now suspecting that I could have TWO faulty GK cables.  So, now I'm going through the painful process of troubleshooting them and their pins with my ohmmeter.  I will let you know what I find out.  These two cables are both 3-footers. One was purchased from eBay and the other came with the US-20 and is a Roland cable!  Also, I was able to reproduce the noise on high gain patches on the GR-55 as well.  So, I don't know. Maybe its the US-20.....The saga continues.
« Last Edit: August 24, 2011, 12:01:05 PM by A to the T »
HEAVY on the METAL
Axe-Fx II, Roland VG-99 + FC-300, Roland GR-55, Digitech Jamman Stereo, Ibanez/ESP/Jackson Guitars

Offline Elantric

Re: US-20 Hum...?
« Reply #23 on: August 24, 2011, 02:45:49 PM »
to debug noise/ground loop issues, Its best to unplug EVERYTHING.

Then connect everything one at a time  - but listen closely for any added noise that arrives with each new gear addition in the signal chain.


 

Offline A2theT

Re: US-20 Hum...?
« Reply #24 on: August 24, 2011, 07:29:01 PM »
Thanks Elantric, yes this was the FIRST thing I did way back when.  Anyway I found a buddy whos coming over tomorrow with a gr20 and another roland cable and we'll try it out.  After todays bout of about an hours worth of troubleshooting I'm almost convinced the US-20 may be the culprit but I wont know until 2moro.
HEAVY on the METAL
Axe-Fx II, Roland VG-99 + FC-300, Roland GR-55, Digitech Jamman Stereo, Ibanez/ESP/Jackson Guitars