Solve USB Audio Noise when USB cable is connected

Started by jon_bondy, February 23, 2008, 11:08:22 AM

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jon_bondy

I just tried my dream setup: VG-99 connected to a laptop via USB using the Editor and with the guitar outputs connected to my amp (as I usually do).  The amp was overwhelmed with electronic noise.  When I pulled the USB cable, the noise went away.  This was true whether the VG was powered or not, and whether the Editor was running or not.  It seems as if the laptop is injecting noise into the VG via the USB cable.

Anyone else have this problem?  Is it a defect in the laptop (which other wise is old but works fine).  Puzzling.

:)

Jon

Elantric

#1
http://www.soundonsound.com/sos/nov04/articles/computerproblems.htm


Classic problem using Unbalanced 1/4" connected Audio Gear in a big Rig with some laptops and the new switching power brick supplies used everywhere today-

Typically one item in your rig (the Amplifier)  is already tied to Earth ground. The Unbalanced 1/4" Sleeve connection on all the  Audio Gear Audio Cable Shields feed this Common Ground to the Roland/Boss processor, and the USB Cable Shield feeds this same  Ground reference to the Laptop  - so technically All gear is still actually Grounded to the Earth. 

But if your laptop employs a Three prong AC Power cord with Earth Ground- your Computer will have a Ground Loop between the AC power cord and the USB Cable Shield. Remember most Windows laptops are Not designed for Audio, and its very common for a Windows laptop to introduce high pitch noise into all your audio signals - this is from the Laptop Power supply.


I had the same problem - but i found a solution.

To debug -

Reconnect all your gear as you like - keep the USB connected to laptop - but try unplugging the Power supply from the Laptop Computer. If the high pitch noise goes away - you found the problem ( its a ground loop from the Laptop's Power supply)

(yea - I know its high frequency "HISSSSSS" you are trying to cure - not 50/60 cycle Ground hum!)


Solution #1  - Run your laptop on its own Battery

Solution #2  - Obtain an Ebtech Hum-X - which filters noise on the AC Ground connection
http://www.ebtechaudio.com/humxdes.html


Solution #3  -  A local  trip to hardware store for a ground lift adapter on the laptop's power supply AC three prong plug-


http://www.adorama.com/ZZAC32.html?sid=1203794455588409

Solved my noise on my HP/Acer/Lenovo Laptops

( and this explains why Macbook Pros use 2 prong AC Power adapters  = lower audio noise and no "switching noise" invading the audio

jon_bondy

I now have all three devices (VG, laptop, and amp) powered from the same power strip.  The problem remains.  If I run the laptop on batteries, the problem goes away, so ti is power supply (switching) noise being injected into the laptop chassis.

You're advocating removing the ground connection for the laptop?  I'm not too worried about that, since the entire device seems to be made of plastic.

Tried using an extension cord that had the ground cut out: solved the problem.

Thanks!

:)

Elantric

Another happy customer:)


QuoteYou're advocating removing the ground connection for the laptop?  I'm not too worried about that, since the entire device seems to be made of plastic.

Actually the Laptop remains grounded via the USB cable to your audio interface inside your the Roland/Boss / Line-6 processor

I cant tell you how many times I have tried to explain the above  solution to people, only to have 3 days of debates from armchair "audio gurus" telling me:
"hogwash - Its Not a ground loop problem!"


Also check that your AMP does have the three prong AC grounded plug -

The Audio cables between the VG-99 and the AMP are providing the ground, the USB cable is grounding the laptop.


Be sure to ground your guitar strings too:

Many people forget to make a critical  connection when using the GK-2A, GK-3

Always Connect the short cable between your Strat's normal output and the  GK-2A Input - its makes the required string ground connection to the GK-2A.
ftp://ftp.roland.co.uk/ProductSupport/manuals/GK-3_OM.pdf

See page 18

"Normal
Guitar Cable
* This connection is necessary not only for playing the
guitar's normal (straight) sound as well as the
guitar's straight sound mixed with the synthesizer
sound, but also for connecting the guitar's ground
and the GK-3's ground. Even if you are not going to
use the guitar's straight sound at all, always make
this connection because of the noise reduction
benefits it provides."

If I remove this short cable - yea I have noise too - it goes away when I reconnect the short 1/4" cable (supplied with the GK-3) between my guitar and the GK-3

Billy Kaffadrin

#4

QuoteI cant tell you how many times I have tried to explain the above  solution to people, only to have 3 days of debates from "audio gurus" telling me "hogwash - Its Not a ground loop problem!"

Also check that your AMP does have the three prong AC grounded plug -

The Audio cables between the VG-99 and the AMP are providing the ground, the USB cable is grounding the laptop.  >>>

     
     Yeah a single ground is quiet, two or more ground points and you have a noisy feedback loop - but a point of caution; NO ground at all might be somewhat quiet  - AND it might kill you.  Typical example is the live gig and a guitar amp with a two prong only connection, and the guy touches a microphone and gets knocked out.  The amp is looking for a path to ground, the PA is grounded, and when the guy touches the mic his body becomes a conduit for the charge. Could happen touching the bass player too, if the Bass amp is properly grounded.  A practical solution if an amp is only two prong, attach a DI between the guitar amp input and an unused channel in the microphone snake.   That creates a path to ground for the ungrounded amp setup, so you doesn't have to be it.

     Sometimes equipment in a rack will ground through their chassis, and you get noise that is hard to track down that way.  But if you lift the grounds on all your gear, it's dangerous.  Good idea to have an outlet phase/ground checker in your bag for checking outlets you plug into on gigs too.

Billy


Elantric


s0c9

Quote from: Billy Kaffadrin on February 28, 2008, 12:28:39 PM
     Sometimes equipment in a rack will ground through their chassis, and you get noise that is hard to track down that way.  But if you lift the grounds on all your gear, it's dangerous.  Good idea to have an outlet phase/ground checker in your bag for checking outlets you plug into on gigs too.

I can't STRESS how important it is to ensure that your equipment is properly grounded when playing live.
Not doing so CAN KILL YOU !!
It really ticks me off when some kid shows up with a new amp with a 2-prong power cable.

Like Billy says, ground noise is sometimes hard to track but is [most] often caused by equipment powered by different outlets on separate circuits -- especially in older buildings. These circuits often do NOT share a common ground [you think this would not be the case] and this causes the buzz. 
As a [small] independent SR [Sound Reinforcement] operator, we mostly run the PA for our own band, but do rent to others - hence have liablity potential.  Power at venues is a constant issue..... finding enough circuits to power 5 power amps [tri-amp sytem with 4 monitor mixes] + backline + lights is quite a challenge.  4000w FOH, 1800w of Monitors. We can run the system off 2 * 15-amp circuits [in a bar], but we prefer 3 or more to be available.

We use a version of the "poor man's power distro" [google it!] where the amp rack is powered by two 15 [or 20] amp circuits. Since all amps in the rack are metal and touch each other, this creates a common ground across both circuits. So no noise !!  We usually run a separate feed to the backline amps from the circuit with the lightest amp load. Anything connected to that [with a 3-pin] is automatically part of the "common" ground. Again no noise.
We also run power to the FOH console off another circuit [or 2nd] and power the rest of the backline off that too. One of the backline is powerd 1/2 from one circuit, half from the other, so that ties your whole system to a common ground - from keys to guitars to bass to mics and power amps.  Our system is VERY quiet.

It takes time to set this up and can co$t some $$ to make happen. Make sure your power distro shares grounds BETWEEN [ACROSS?] your EQUIPMENT and do not assume the venue is adequately grounded.  In 3 yrs we have not had a single complaint of someone having their lips "tingle" when touching their mic.

If THAT tingling does occur, you have a grounding problem, and its a sure sign of impending DANGER !!  Have folks down guitars, etc and power down their gear until you find it and fix it. 
DO NOT LIFT THE GROUND ON ANY GEAR TO RESOLVE THIS.  IT is EXTREMELY DANGEROUS.

Keep in mind that when you run a PA system at volume, you are running up to a 30+ amp load for your average bar gig. Between sets, that drops off to nothing... merely milliamps. If that 30+ amps suddenly decides to find its way to ground thru you mid song... Adios amigo. Need I say more... ??

Large systems are [20,000+ crowd] usually not prone to this as they often have their own gennies and electricians. Bars, clubs, halls etc, are often VERY badly wired... I urge CAUTION. Buy a $6 circuit/ground tester @ Lowes/Home Depot. It may save your life.

Sorry to ramble, but I've seen people get hit by ground faults and it is NOT pretty. After reading Billy's comments, I felt some clarification was in order..

-Steve

Elantric


Billy Kaffadrin

Quote from: s0c9 on February 29, 2008, 08:43:08 PM
Sorry to ramble, but I've seen people get hit by ground faults and it is NOT pretty. After reading Billy's comments, I felt some clarification was in order..

-Steve

    Well, the phasing of electrical outlets and the availability of dedicated audio power with a single ground reference are issues beyond the control of most guys doing small-medium size gigs.  But the idea of "Star Grounding"/a single ground point is a practical thing to get in people's minds regarding troubleshooting their individual rigs I think.  Certainly when the audio guy tells you not to use *that* power outlet though, use *this* one, people should do it.

    But even with dedicated audio power, when faced with an amp with a two prong plug or worse also having a two prong plug on their European 220 to 120 volt inverter for their pedalboard/amp rig, you have got to ground the setup somehow.  The DI solution is easier than running a ground wire from the amp chassis to the stage monitor mixer's chassis, and you can't just let guys kill themselves on your watch...

Billy


truth57

I have an Acer Aspire laptop, and with this computer, this problem seems quite severe. Also, being a European model bought in Spain it does not have a three pin plug, and generally the older houses like mine do not have an earth wired into the circuit. So I am not sure how to go about implementing the recommendations that have been made here in earlier posts.

It is definitely the laptop's power supply that is the problem, as even with the VG-99 connected to the USB port of my desktop which is in no way connected to my laptop (other than by wireless, but not as a network) if the audio out of the VG-99 is connected to the audio in of the laptop the same noise is generated and goes away when the adaptor is disconnected from the laptop.

Due to the lack of available 64 Bit drivers I cannot use the Acer laptop either to edit the VG-99 or record direct from it via USB, but I have decided to try a solution.....

I found a Phonics mixer with a Firewire connection (Phonix Helix 12 Firewire MKII) that is claimed to have full support for Windows Vista 64 Bit OS, and that will hopefully allow streaming of 10 channels of audio into my laptop and its software applications for DAW. This will hopefully also allow me to monitor and mix the other instruments in my home studio setup, although very basic (in addition to the VG-99, just a VG-8EX, an EMU Proteus 2000, a Midiman Midisport 4x4 and various VST plugin instruments), as well as allow me to solve the EQ disparity problem I am presently experiencing when trying to use the VG-99 in a live situation.

As many others have stated, there really is a big difference in EQ between sounds mixed through headphones and the subsequent sound when heard through a PA system, even though everything is absolutely flat on the mixer in terms of EQ; everything sounds way too thin, and requires radical re-EQ'ing within the patches themselves.

I have decided to do away with my power amp and purchase a pair of powered reference monitors, in the hope that their flat response will help me to correctly adjust the EQ for live use. However I suspect that there is in fact a disparity between the EQ of the headphone outs and the mix outs of the VG-99, which would account for the problems many of us have been experiencing. As you can tell, I have very little knowledge and understanding in this field, but am hoping bit by bit to acquire the necessary information to enable me to work successfully with the system.

Thanks,

David

sixeight

You definately need a properly grounded power outlet if you want to do anything with a computer and recording sound. I also have a house without properly grounded outlets, but I have taken the trouble to get a properly grounded outlet close to my computer. Without it, i would not be able to get a "clean" recording of a distorted guitar (distortion makes noise and hums worse).

truth57

Quote from: sixeight on April 29, 2008, 05:39:20 AM
You definately need a properly grounded power outlet if you want to do anything with a computer and recording sound. I also have a house without properly grounded outlets, but I have taken the trouble to get a properly grounded outlet close to my computer. Without it, i would not be able to get a "clean" recording of a distorted guitar (distortion makes noise and hums worse).

Thanks Sixeight, I am in the process of trying to sell the house, so it is not worthwhile investing in such a rewiring/grounding project, but I am going to make sure that my next property choice will be more modern and suitable to my home studio. But in the meantime this noise is driving me nuts  ;D.

The laptop itself seems to make no such noise unless the VG-99 is plugged into it (or connected to my desktop), and what makes it even worse is the USB connection as already mentioned. So it looks as though I am going to have to do my sound designing monitoring directly into my headphones, and that should solve the problem.

However I had hoped to be able to do all my editing and recording using my far more powerful laptop, but unless I am able to successfully install Windows XP on the SATA drives, that is not going to be possible.

David

truth57

In the interim I managed to get a version of XP Pro to run within Vista 64 Bit in VMware. I now have the VG-99 connected to my laptop via USB and notice that it makes far less noise than it did when connected to my desktop PC. I have no idea why, because the last time I tried connecting it to the USB port of my laptop it produced far more noise, yet now it is relatively quiet, even without removing the power supply from the laptop.

There is no separate ring main to separate wall sockets from lighting circuits here, so it might be that the noise is worse when the refrigerator is running or something similar. I certainly noticed that this made a big difference while trying to run DAW applications with my desktop PC.

I also believe that there must be some sort of earth loop problem with the wiring from the desktop PC. So this has been a step in the right direction.

David

beatpete

I had the same problem with my Phonic Helix 24 firewire board. Lifting the ground on the laptop completely cured the problem. As far as safety goes, the entire system is STILL grounded via the Phonic board and the connected audio/firewire cables. I assume that this would be the same with the VG-99 EXCEPT that it uses a DC power suppply and I'm not sure if that supplies adequate ground. If there's a grounded amp in the equation, then I think lifting the grounds from everything except the amp would work AND be safe. Basically, you want to avoid ground LOOPS and I think this gets really noticeable when using a computer.

truth57

Quote from: beatpete on May 11, 2008, 09:58:00 AM
I had the same problem with my Phonic Helix 24 firewire board. Lifting the ground on the laptop completely cured the problem. As far as safety goes, the entire system is STILL grounded via the Phonic board and the connected audio/firewire cables. I assume that this would be the same with the VG-99 EXCEPT that it uses a DC power supply and I'm not sure if that supplies adequate ground. If there's a grounded amp in the equation, then I think lifting the grounds from everything except the amp would work AND be safe. Basically, you want to avoid ground LOOPS and I think this gets really noticeable when using a computer.

Thank you Pete. Incidentally I just received my Phonic Helix 12 board, so it will be interesting to see how it fares combined with my Vista 64 Bit laptop and the VG-99. The VG-99 itself has a ground lift switch, and I did try it without noticing any perceptible change. A friend of mine who also uses an Acer laptop had the same problem, but apparently solved it by wiggling about the connection in the DC adaptor. According to him the problem is especially noticeable in Acer laptops, but having little experience with other makes I cannot verify that. But what I can say is that when the VG-99 is plugged into the USB port of my desktop, the noise produced via the laptop (which is my monitoring source until I configure the Helix board) is increased substantially. It is digital noise too, with an audible digital clocking effect. I am really hoping that once I have everything running via the Helix board and the Firewire interface this will solve the problem, but it makes editing the VG-99 very difficult, because of that noise.

Thanks,

David

Elantric

#15
If you read my inital reply to this thread - you will find what is the cause of this digital white clocking noise - its due to the switching power supplys used on all the gear including the VG-99, and  the Laptop.

The VG-99 includes an actual Chrome Ground Screw to assist in grounding the VG-99 chassis.

In my use, I typically use the VG-99 with a Macbook Pro - never have noise issues.

I also have a HP ZD7000 Notebook - and with that machine I must use the ground lift adapter (see my earlier post) anytime I attach the VG-99 Output to an external GROUNDED  Power amplifier.

Observe - All gear has a Ground Path - the USB Cable is grounding the Laptop through the VG-99,   which is grounded to the Power Amp (through the VG-99 Output Cables) 

Employing ground loop isolation strategies solves the digital white clocking noise. The Power Amp has a good ground connection and the audio cable shields pass this "safety ground" to the VG-99. Even a USB cable has a Ground Shield and ground connection- this becomes the  ground reference for the Notebook via the VG-99. 


truth57

Quote from: sustainiac on May 12, 2008, 08:03:01 AM
If you read my inital reply to this thread - you will find what is the cause of this digital white clocking noise - its due to the switching power supplys used on all the gear including the VG-99, and  the Laptop.

The VG-99 includes an actual Chrome Ground Screw to assist in grounding the VG-99 chassis.

In my use, I typically use the VG-99 with a Macbook Pro - never have noise issues.

I also have a HP ZD7000 Notebook - and with that machine I must use the ground lift adapter (see my earlier post) anytime I attach the VG-99 Output to an external Power amplifier.

Employing ground loop isolation strategies solves the digital white clocking noise. The Power Amp has a good ground connection and the audio cable shields pass this "safety ground" to the VG-99. Even a USB cable has a Ground Shield and ground connection- this becomes the  ground reference for the Notebook via the VG-99. 


Thank you forgive me if I am having a hard time keeping track of the posts on these forums.....however there are two issues that set this setup apart, one is the lack of earth I already mentioned in the house, which is something I cannot change right now, and the second is that my VG-99 was connected to my desktop but still producing noise in the laptop because I am using its soundcard to monitor the output. That is an issue that should be resolved by using the Firewire card of my Phonics desk.
However I now have an issue with the drivers for the desk, Windows Vista refuses to allow me to use unsigned drivers and Phonic customer support inform me that this can be worked around within the user permissions of Windows Vista 64 Bit, but I've already tried everything and cannot find where I need to make the necessary changes in the system.

Regarding the ground lift on the VG-99, I bought mine from the UK, and the plug it comes with has a plastic replacement for the ground pin, so I very much doubt it has any effect whatsoever. In fact the plug itself consists of a 2 pin to 3 pin adaptor with a plastic 3rd (ground) pin. Seems pretty ridiculous to me...

Here in Spain, the newer plug sockets have a border in both the plug and socket that connects to the ground wire. The problem is that in older properties this is not the case and there is no actual ground wire in the house. That is the way of it here. Now I should mention that as my active monitors have still not arrived, I am presently continuing to use the cheap stereo tuner CD combo in order to take the outputs from the desk, and there is absolutely no noise via the desk itself. This is because the VG-99 output is going to the desk rather than to the laptop soundcard as before. So once the driver issue is resolved the ground loop problem should also be resolved.

I think the Phonic desk is excellent quality by the way, very clean and transparent. Can't wait to get the active reference monitors. The VG-99 through the sub outs sounds way too toppy, just the problem I have in rehearsals and when playing in church. But now I can hear the same thing here, so I can start to look for a solution.

Thank you for your help....

David

Elantric

#17
FWIW - In Many countries around the globe -  You can improvise a Earth connection by using the nearest Cold Water Pipe -

Its best to find where it enters the house ( and check that it is 100% Electrically Conductive metal!)

In the USA - the Telephone company always has a Ground Clamp located on the Cold Water Pipe -


  - this IS the Earth Ground - and you could feed a 12 gauge wire to your studio room and call this "Ground".

http://www.hardwareandtools.com/invt/6439038?ref=gbase

truth57

Quote from: sustainiac on May 12, 2008, 10:30:57 AM
FWIW - In any country around the globe -  You can improvise a Earth connection by using the nearest Cold Water Pipe -

Its best to find where it enters the house

In the USA - the Telephone company always has a Ground Clamp located there already.

  - this IS the Earth Ground - and you could feed a 12 gauge wire to your studio room and call this "Ground".

http://www.hardwareandtools.com/invt/6439038?ref=gbase

Thanks Steve, that sounds like a far better suggestion than ramming a steel rod into the ground, which is how it is done here  ??? The water mains is a plastic system, but where it enters the butane water heater the piping is copper, would this serve? There is also another cold water outlet to an external tap, could that be used?

Regards,

David

Elantric

#19
You will want to locate the actual Main Water entry for the House. This should be a metal Pipe.

Its best to FIRST check that it is 100% Electrically Conductive metal!)



Re: The Copper Cold Water Entry to the Water Heater - Be sure this Copper Cold Water Entry is emerging from the Ground - if "YES"  - install the Ground Clamp there.

If your Cold water supply pipe is Plastic - then DO NOT USE THIS CONNECTION.

BTW - they do use a very long Copper stake into the ground, if the Cold Water Entry is not available - or too far away from the Studio.

If you can locate a local HAM radio operator there in Spain - he should be able to help you with advice on the best local method of achieving Earth Ground connection for your Home Studio.   

https://en.wikipedia.org/wiki/Ground_(electricity)

https://www.erico.com/selectCountry.asp?returnURL=%252Fpart%252Easp%253Fpart%253D615880

https://www.erico.com/part.asp?part=615880


MikeC

I've just spent an afternoon trying (sucessfully) to fix this very problem in my setup. I'm running a Desktop PPC Mac Dual 2Ghz, with a MOTU 828mkII and MTP AV for audio and MIDI interfaces. All my rack gear is powered from one well shielded and filtered mains extension block. My guitars, amps and VG99 are located about 20 feet away in a 'performance' area. All the performance gear was powered from a different shielded and filtered mains extension block. To reach the Mac USB ports, my VG99 and my POD X3 ran via an Active USB Extension. Both POD and VG99 gave out excessive noise including clock signal oscillation - POD was significantly noisier than VG99. Additionally, the VG99 was running through a powered hub before the Active Extender cable.

Today I experimented with re-cabling:
1) running the POD & VG99 from the Mac's power block - slightly less noise from the VG99, no change from the POD
2) running USB cable into a passive extender then into the Mac, cutting the powered hub out completely - complete lack of noise from the VG99, no change from the POD; the POD actually produced noise at a lower level even when it was powered down!
3) finally tried lifting the shielding on a USB cable - both devices worked, but no real change to the noise levels (though the VG99 became susceptible to USB cable handling noise)

I'm happy that I've cured the noise problem for the VG99 at least! (though I have to keep an eye on the USB cable running at ankle height into the front of the Mac!) ;D

MIke

MikeC

More good news. Just fitted a Sonnet Allegro USB 2.0 card into my Mac G5. Plugged the POD X3 in first and ... bliss! the noise was gone. Added the VG99 and still nothing. Now I can get back to the music!  :)

Mike

fokof

I had a nasty ground loop once on my "mobile" kit and the only way I got rid of it was by cuting the ground wire from  the USB cable (black). nothing else worked but that did the trick.

Maybe it can help someone.....

jackyl666

I have just started to use the VG-99 attached to my desktop and have a hum, tried cutting the black wire and had no luck still had the hum even louder now.

I have unplugged the computer figuring it was a ground loop, still have the hum. unplugged the VG-99 still there. unplug the cable between the two and it goes away. I am completely at a loss. It is not a terrible hum and probably not noticeable at normal levels but when I increase the line level on my mixer I start to hear it.

The ground lift on the VG-99 looks to only work on the balanced outputs from what I can see on the lines attached to the back of mine. Correct me if I am wrong, but it certainly looks like it on mine, either way it does nothing. 

baatkarlo

69 cents for a single cheater plug at Home Depot plugged between laptop power cord and socket resolved my ground loop problem. However, I then read the below link and am thinking of getting a DI at the main and sub out ports in the back of the VG-99.

http://bose.infopop.cc/eve/forums/a/tpc/f/6806048934/m/1171031006

My question is - how high is the risk ogf putting a cheater plug between laptop power plug and socket as compared to one between the amplifier's power cord and socket? The laptop does a step down conversion from 110v to 9v or something similar and pulls less curent, while an amplifier will often ste up to higher voltage and curent to drive speaker coils. 
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