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Experience of noise from USB power?

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Experience of noise from USB power?

Postby Urumiko » Thu Oct 12, 2017 10:49 am

HI,

Forgive me if this is a topic i've brushed on before.
I currently use a steinberg UR22 MK1 interface for basic guitar DI recording and find it a bit prone to interference.

Previously I was troubleshooting this on my desktop and found it to be directly related to the USB connection to the PC, I found if i grounded the PC it was attached to it would reduce the noise level.

I recently moved to a Dell XPS 15 9560 laptop and found similar issues.
I found fairly persistent digital interference.
I also found that if i disconnected the laptop charger from the laptop this would reduce somewhat.

As i understand it this is noise coming through the ground that is shared with the int and then ultimately therefore with the guitar input as opposed to RF interference.
Beyond splicing cables and things i guess this is just an inherent issue of a cheap audio interface. Has anyone else found this with bus powered interfaces?

I'm hoping that if i graduate to a mid/high end interface which would probably have external power this issue should hopefully disappear. Should I just avoid bus power all together?

It's getting a bit frustrating when i go to lengths to avoid interference but its coming from the computer i need for recording =)
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Re: Experience of noise from USB power?

Postby Urumiko » Thu Oct 12, 2017 10:58 am

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Re: Experience of noise from USB power?

Postby Kwackman » Thu Oct 12, 2017 11:10 am

Urumiko wrote:What do we think of this?

http://www.audioquest.com/jitterbug/jitterbug

"Improves dynamic contrast, warmth and resolution"
My BS alarm went off when I got to this bit......
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Re: Experience of noise from USB power?

Postby Urumiko » Thu Oct 12, 2017 11:44 am

Kwackman wrote:
Urumiko wrote:What do we think of this?

"Improves dynamic contrast, warmth and resolution"
My BS alarm went off when I got to this bit......

Haha yeeeeeah. I saw a guy on youtube take 3 different brands of these and hook them up to his Turntable>DAC>jitterbug>Laptop, then start talking about different emphasis of frequencies...

The point is, what I hope it is.. is effectively a USB power conditioner, though the manufacturers website sprouting that kind of BS does put me off.
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Re: Experience of noise from USB power?

Postby Hugh Robjohns » Thu Oct 12, 2017 12:00 pm

The problem you are dealing with is that interference can manifest in many different forms, and each situation usually requires a different solution... but to arrive at the optimum solution you need to work through the problem very methodically to determine the exact cause.

Electric guitars are basically large aerials and will pickup interference the moment you plug them in... so it's best to check out the rest of the system first to make sure that the interface/compute/monitor speaker elements (and anything else connected) are clean.

In all systems with multiple earth connections there is the possibility of one or more ground-loop(s) which typically manifest as continuous audible hums or buzzes systems in analogue systems, or unreliable data connections in digital systems.

Ground-loop noises are always the result of poor equipment design, and tend to be most problematic in systems that have mains earth connections, as the loop can then extend around the building's mains wiring.

So, this mostly affects Class-1 mains powered equipment which has exposed metal work bonded to the mains safety earth.

Where there is a ground-loop, it is most commonly found between the mains-powered computer/interface and the mains-powered monitor speakers. The solution usually involves breaking any identified ground-loops in the audio grounds of the connecting balanced cables (never the safety mains earths), typically by using audio isolating transformer boxes like the ART DTI or Cleanbox2.

I doubt this is your problem, though.

In the case of laptops and their power supplies, as well as a lot of synths, keyboards and other modern/budget audio equipment, most have Class-2 or 'double-insulated' mains supplies which don't have a mains earth connection, and so the likelihood of ground-loop problems is greatly reduced... but a different problem emerges which is a complete absence of a reference ground.

As your interface is bus-powered there can be no ground-loop between interface and computer. Moreover, if your laptop has no mains safety-earth connection via its power supply (or you're running it on its battery), it will have no ground connection at all!

In this case the whole audio circuitry essentially 'floats' and acts as an aerial to such nasty noises from the ether. The 'screening' around the circuitry and cables, designed to stop interference getting in, is not grounded and so instead of the interference signals being promptly taken away to ground they are injected directly into the audio signal path.

The solution, in this kind of situation, is to provide a proper reference ground to the whole system, usually by connecting the mains safety earth to a signal ground point in the equipment. There are myriad ways of achieving this, depending on your DIY and electrical competence, but the safest way is by using something like the Groundology plug which I reviewed here: (note some simple soldering will be required to attach an appropriate audio connector)

https://www.soundonsound.com/reviews/gr ... ction-plug

With the system properly grounded, there should be no interference at all, and it should be as quiet as you would want it to be... until you plug in a guitar.

The magnetic pickups on the guitar are also quite capable of picking up other E-M fields in the room, and the relatively high impedance of the internal wiring and interface input also make it very prone to serving as an aerial to collect more interference. Single-coil pickups are worst for this... and that's why humbuckers were invented.

You can now get humbucker replacement pickups that sound like single coils, and I would recommend them if interference is a problem. It also pays to spend some time and effort on properly screening the wiring cavity in the guitar using adhesive copper sheets, and also on making sure that the grounding inside the guitar is sensible and doesn't, itself, contain ground loops. All the earths should meet at one single point only, ideally on the jack socket -- although most designs seem to terminate earths on the back of the volume pot.

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Re: Experience of noise from USB power?

Postby Hugh Robjohns » Thu Oct 12, 2017 12:01 pm

Urumiko wrote:The point is, what I hope it is.. is effectively a USB power conditioner, though the manufacturers website sprouting that kind of BS does put me off.

No, it's not a power condition, it is intended to help reduce jitter on the USB data signals. It wont help your situation in any way at all.

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Re: Experience of noise from USB power?

Postby resistorman » Thu Oct 12, 2017 12:48 pm

I had a strange problem come up the other day with usb noise. I hooked up a Linnstrument and a keyboard controller into an iConnectivity 4+ via a usb hub and got some annoying buzzing sounds, but when I attached the usb hub’s power supply, it got dead quiet. Power draw?
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Re: Experience of noise from USB power?

Postby Urumiko » Thu Oct 12, 2017 1:30 pm

Cheers hugh.

Yeah we went through most of this with my desktop in an older thread. I even disconnected my monitors, and visual monitors, turned off my router and everything and still had the noise with just the PC and interface turned on.

In this case im on a different room with just the laptop and the noise is very digital and very much coming from the PSU of the laptop as much as i can tell.

THinking of things I have lying around the house, I'm the kind of guy that cuts plugs off old appliances before throwing them away, i also have a soldering iron, old USB cables, resistors, caps, prob not any transformers. If i were to take an old plug, and experiment with connecting the ground pin to various points in the circuit would i need anything in there like a resistor or fuse?

Any place you would suggest i try first?
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Re: Experience of noise from USB power?

Postby Urumiko » Thu Oct 12, 2017 1:39 pm

resistorman wrote:Power draw?

Sounds like the instrument was earthing itself via the 4+, then when you connected the power supply it gave it a better earth?
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Re: Experience of noise from USB power?

Postby Hugh Robjohns » Thu Oct 12, 2017 2:55 pm

Urumiko wrote:If i were to take an old plug, and experiment with connecting the ground pin to various points in the circuit would i need anything in there like a resistor or fuse?

No fuse or resistor required.

However, I'd probably remove the fuse-carrier and screw terminal from the line/live pin and/or (depending on the design of the plug) insulate the line/live (and probably the neutral as well) inside the plug body, just so that should the earth wire come free of the earth pin, it can't accidentally touch the live pin as that wouldn't be good!

At the other end of the earth wire, solder it to the sleeve of a jack plug, or put a croc-clip on it so that you can plug it into a spare jack socket to connect the equipment audio ground to mains earth, or clip the croc-clip onto some suitable grounded metalwork.

Any place you would suggest i try first?

I'd ground the interface via a spare input or output socket, headphone socket, something like that.

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Re: Experience of noise from USB power?

Postby ef37a » Thu Oct 12, 2017 9:02 pm

With regard to possibly 'dirty' USB power? I doubt it.

I doubt Hugh & co dabble with the 'projjy' end of the market much so maybe I can give my 2p'oth?
In the last 10 years or so I have had several USB AIs and a variety of desk and laptop computers. None have been top flight and quite a few very bargain basement.

AIs include M-A fast track pro, Behringer BCA2000, Alesis i02 Express, Tascam 144. Currently I have the NI KA6 and a Focusrite 8i6. None of those interfaces used with a variety of laptops etc have ever given me the slightest trouble with noise from the USB connection (I did get a hum loop with the KA, powered monitors and a laptop on charge but going to battery power fixed that)

Indeed the KA6 always returns an un weighted noise floor of better than -100dBFS with any of 3 machines with no input at min gain. The WORST noise floor I get is from a Behringer UCA 202 at about -80dBFS but that is still plenty good enough for tape dubbing!

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Re: Experience of noise from USB power?

Postby Urumiko » Tue Oct 17, 2017 12:15 am

Cheers dave... up with this i shall not put
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Re: Experience of noise from USB power?

Postby Urumiko » Tue Oct 24, 2017 8:54 am

Update:

so. I tried the ground plug approach, I effectively cut the end off a guitar cable and wired the shield to the earth pin of a standard uk plug. and experimented with plugging this in all the sockets on my interface

At high gain this did give a noticeable reduction in base level hiss and certainly worth doing, but made no impact whatsoever on the more prominent mechanical sounding interference. The only thing that seems to work is turning off HI-Z on the input.

To re-iterate ti's a series of rapid beeps, i'd be quick to assume was wifi or powerline Ethernet, perhaps a monitor. Something like that. I tried un-plugging the electronic devices around me and this did remove some noise, I also unplugged the laptop charger and this eliminated yet more noise, but the single most prominent and distinct source of noise remains.

I have done this before to no effect when using my desktop, but my next step is to effectively turn off every electrical device in the house, I might even throw the mains breaker, and run my laptop on battery, and see if the noise persists. It certainly sounds like a device is kicking out RF interference. I've tried on 2 PCs in 2 rooms with about 4 guitars, monitors, and headphones, so i don't think it's them alone at fault. The only thing that has remained common is the interface and the wider house.
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Re: Experience of noise from USB power?

Postby ef37a » Tue Oct 24, 2017 8:59 am

"A series of rapid bleeps"?

Sounds like a mobile phone.

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Re: Experience of noise from USB power?

Postby Hugh Robjohns » Tue Oct 24, 2017 9:04 am

It's not unusual to have mulitple separate interference issues. Clearly, an absence of a ground to some of your equipment was a part of it as the noise improved when you attended to that.... but interference from something unknown is still getting into the system somewhere.

Firstly, you need to track down where that interference is getting in. Only then will you be in a position to figure out how to stop it getting in -- and that might mean tracking down the source and eliminating it. Unplugging stuff at random all over the house won't help you focus on what's going on. You need to be more logical and thoughtful about it than that.

So, simplify the system to it's basics: Are the speakers clean and interference-free on their own? Are the speakers still clean when connected to the interface on its own? Are they still clean when you attach the computer to the interface... and so on. Work carefully and logically and you will find out where the interference is getting in. Once you know that we can figure out a way to deal with it.

But as Dave says, blip-blip noises could very well be a mobile phone too close to something.

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Re: Experience of noise from USB power?

Postby Urumiko » Tue Oct 24, 2017 11:14 am

Thanks all,

The noise is a high pitched constant pulsing that does sound like a wifi or other data connection causing RF to me. The first culprits were powerline ethernet/router.

When this was happening on my desktop (which is not a wifi device), I got to the point where i had all of my VDU monitors and audio monitors etc turned off and disconnected, I also had my network router and all adjacent tech turned off, as well as all of my powerline ethernet throughout the house disconnected, I just had the desktop running with the USB powered interface and a guitar attached. I set it to record and the noise was still there.

Now i'm on my laptop and the interface has no monitors or powered instruments connected just headphones.

You make some good points. I need to make sure any mobile phones are turned off, I also wear a bluetooth fitness band which didn't occur to me before. And there's the wifi/bluetoothi on the laptop itself too! This wasnt an issue with the desktop but i cant rule that out.
I guess i could also shut the laptop display off by closing the lid to rule out the inverter on that.

watch this space...

P:S. would parking up in a field in the middle of nowhere with my laptop and an earth rod be too far? lol
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Re: Experience of noise from USB power?

Postby ef37a » Tue Oct 24, 2017 11:19 am

Laptop in car in field might tell you something but belay the earth rod!

That would make you an excellent MWave receiver.

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Re: Experience of noise from USB power?

Postby Hugh Robjohns » Tue Oct 24, 2017 12:54 pm

Urumiko wrote:i had all of my VDU monitors and audio monitors etc turned off and disconnected, I also had my network router and all adjacent tech turned off, as well as all of my powerline ethernet throughout the house disconnected, I just had the desktop running with the USB powered interface and a guitar attached. I set it to record and the noise was still there.

But was it there without the guitar plugged in?

If not, then the guitar is the aerial picking up the interference -- whatever the source -- so the first next step must be to minimise the guitar's sensitivity to external interference by checking it's earth continuity, shielding its control cavity, and so on. Alternative hum-bucking pickups might also be an option...

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Re: Experience of noise from USB power?

Postby Urumiko » Tue Oct 24, 2017 1:28 pm

Hugh Robjohns wrote:
But was it there without the guitar plugged in?

If not, then the guitar is the aerial picking up the interference -- whatever the source -- so the first next step must be to minimise the guitar's sensitivity to external interference by checking it's earth continuity, shielding its control cavity, and so on. Alternative hum-bucking pickups might also be an option...

H

Hi Hugh, ill double check, but from what I remember no real noise above background with nothing plugged in, I don't think my cavities are shielded but it was happening with both my Gibson LP, and PRS C22, and my bass. Hum buckers did squat. I think I'm right in saying it did it with just a cable connected and held mid air too.

I will check
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Re: Experience of noise from USB power?

Postby Urumiko » Mon Nov 06, 2017 8:01 pm

HI,

Sorry for the delay in updating this. I got a day off work today and had a chance to experiment some more.

First thing i did was turn off everything electrical in my house, even lights, the boiler, everything.

My laptop (dell xps 9560) was connected to the wall via the charger, my interface (UR22 MK1), was connected via usb, which in turn had headphones and a guitar cable connected.

With no guitar cable connected everything is silent as you would expect.
With just the guitar cable and no guitar connected, everything is noisy as hell.

I tried connecting both my PRS C22, and by bass, and found the same problems with both.
The bass is lower output so the problems were more prominent.

Problem one: a low (ground?) hum. this is is a constant low hum, Grounding my USB interface with a ground plug does nothing, I also get a slight pop if i touch the strings on my bass. Touching the laptop (carbon fibre based, reduces the hum about 50%), turning the charger off at the wall does nothing, but disconnecting the charger completely stops the hum altogether. I distinctly remember this issue occurring on my desktop also where i was getting a pop when touching my guitar strings or bass strings.

Moving downstairs seemed to improve this some though not completely.
The wiring in my house is fairly old as I have a fuse box with actual fuses.
I hope to replace this soon when i have the studio room rewired, though im wondering if there are any special earth related requests i need to put to the electrician.

Problem 2, The "digital interference", Both the laptop and the charger seem to emit a "coil whine" with a pattern which matches the interference im picking up. Holding my ear to the laptop or charger I can here them. Holding my guitar close to the charger or laptop picks this up loudly, but it is still present if i sit as far away as possible. Humbuckers make no difference.

Again though running on battery stops this all together.

So from this i seem to be concluding that the power pack and the battery charging circuit in the laptop possibly? are emitting a lot of RF interference? what are my options.

I had been planning to move to a dell TB16 Thunderbolt docking station in the studio, which means power delivery will be by another method, so i could get lucky there, but the docking station still ultimately uses a similar charger so i don;t know :/

Is this a common issue? do i need to build a Faraday cage arround myself when tracking guitar? lol.
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