Need help with (ground) noise when connecting Electric Guitar with Audio Interface.

[vlandes]

Hey everyone. Recently I bought an electric guitar, and I notice a loud humming noise when I connect it to my audio interface. The noise goes away pretty much completely when I touch the strings. So it probably has something to do with grounding, but I've tried SO many things by now I feel like I'm running out of options. I use a TS cable to connect the guitar to the interface (Steinberg UR22mkii). . The interface is connected via USB to my desktop PC. There's a 'Input Hi-Z' function on the interface which I have enabled when I have the guitar connected.

There was ONE instance where the noise was gone. That was when I hooked the audio interface up to my laptop, and disconnected the power adapter (so it was running on battery power). This unfortunately isn't an option for me to record, since I have a PC which I use for that stuff.

Here's the things I tried to solve the issue:

I've tried to power the audio interface seperately via it's 5v dc switch but that didnt help. I've tried a DI box, that didn't help either, the ground lift button didn't do anything. Ive tried connecting my pc to both a grounded and a not-grounded outlet, did not make a difference. I tried turning off ALL my electronics on my desk (displays, monitors etc.) except for the pc, that didn't work either. Tried connecting the interface to different USB ports, no luck either..

One last thing to note, is that I do live in an old townhouse (1910). Bad wiring perhaps? Bad ground connection? I haven't had any electrical issues since I moved in.

Does anyone have an idea how I might be able to solve this? Its quite frustrating, I purchased this guitar to record with it... Thanks in advance!

[ajay_m]

I would try a usb isolator using an adum3160 optical isolator and power the ur22 from a 5v supply. You can pick one of these up for under £15 on eBay and they do generally resolve problems like this, though not always unfortunately.

[Wonks]

What is the guitar? Single coils or humbuckers?

Fully floating systems on a battery can be remarkably silent and then noisy with an isolated class 2 PSU due to a lack of solid ground. But an external USB PSU should provide a good ground.

Touching the strings and the noise stopping does indicate the system is grounding your body, both stopping it acting as an aerial for noise and making your body act as a shield.

If it’s mainly pickup-based, then turning round should find a location where hum is minimal.

So if you’ve got a Strat or Tele or something else with single coils, which do pick up a lot of hum, then you might need shield the cavities and/or fit noiseless pickups.

[ajay_m]

I haven't tried these on a guitar https://www.amazon.co.uk/Packs-Ground-I ... plfs&psc=1

but I can say they work very well in some difficult grounding scenarios. I am not quite sure what loading they would impose when connected to a Hi-Z input, my transformer theory is a bit hazy, but they are cheap and they are surprisingly good quality (I measured natural resonance at well over 100KHz as I recall)

[Jimmy B]

When I had a similar issue a few years ago, I grounded the audio interface by plugging a guitar cable into one of its spare inputs, and the other end into a real guitar amplifier. It might be worth trying this, if only to eliminate it from the many possibilities.

[Wonks]

I haven't tried these on a guitar https://www.amazon.co.uk/Packs-Ground-I ... plfs&psc=1

but I can say they work very well in some difficult grounding scenarios. I am not quite sure what loading they would impose when connected to a Hi-Z input, my transformer theory is a bit hazy, but they are cheap and they are surprisingly good quality (I measured natural resonance at well over 100KHz as I recall)

Probably 1:1 as it’s just an isolating transformer, so IIRC, the guitar would see the hi-Z input impedance of around 10k ohms. But as the guitar has no ground connection of its own, it probably won’t cure any hum.

[vlandes]

I would try a usb isolator using an adum3160 optical isolator and power the ur22 from a 5v supply. You can pick one of these up for under £15 on eBay and they do generally resolve problems like this, though not always unfortunately.

Thanks for the response!
I've seen others mention something like this online, its definitely worth a shot, especially since they're not that expensive indeed. I also saw someone mention the ifi iDefender (https://ifi-audio.com/products/idefender3-0/) I assume its the same but more expensive?

[vlandes]

What is the guitar? Single coils or humbuckers?

Fully floating systems on a battery can be remarkably silent and then noisy with an isolated class 2 PSU due to a lack of solid ground. But an external USB PSU should provide a good ground.

Touching the strings and the noise stopping does indicate the system is grounding your body, both stopping it acting as an aerial for noise and making your body act as a shield.

If it’s mainly pickup-based, then turning round should find a location where hum is minimal.

So if you’ve got a Strat or Tele or something else with single coils, which do pick up a lot of hum, then you might need shield the cavities and/or fit noiseless pickups.

Thanks for your response! The guitar is a squier stratocaster, so single coils? Ive read that strats can be quite noisey by themselves. Any recommendations for a 5V external powersupply for the interface? According to the manual, the output voltage should be: 4.8 V to 5.2 V and the output current: 0.5 A or greater.

Tried turning around, standing in different parts of the room, didnt help unfortunately.

I should also mention that the noise decreases in volume when I touch the strings, Im just realising this now that Ive cranked up the gain more with Hi-Z turned on.

[vlandes]

When I had a similar issue a few years ago, I grounded the audio interface by plugging a guitar cable into one of its spare inputs, and the other end into a real guitar amplifier. It might be worth trying this, if only to eliminate it from the many possibilities.

Hah that might actually be a good idea to try! My sister has a small guitar amp I can borrow, I'll try it tomorrow!

[Wonks]

Yes,a Squier Strat will normally have three single coils.

It's sounding more like a lack of ground.

A standard USB charger plug will do (2.5W or greater output), and you'll need a micro USB connector on one end and whatever the USB charger plug has (USB-A probably) on the other end. It may not even need to be turned on in the socket if not selected as the power source as it should still carry a ground connection through on the 0v rail.

But the guitar amp idea is definitely worth trying, provided the amp has a mains power lead or IEC mains socket, and not an external PSU.

You can also try the guitar straight into the guitar amp, to get an idea of how much hum is normal for the guitar.

[vlandes]

Alright, here's an update.

So I borrowed a pretty nice amp, a Marshall CODE25, and the noise EVEN occurs when I just connect the guitar to that thing. I tried both a grounded and non-grounded outlet, didnt change a thing. When I touch strings or metal parts of the guitar, the noise decreases in volume..

So now im worrying that it's either the guitar, or even worse, bad wiring in my house.. Any advice?

Thanks in advance, and for all the help in general!

[Philbo King]

One thing that can help:
Copper tape or conductive paint in the electronics cavity of the guitar, with a wire connecting it to ground.

A story -
I once had a punk/metal band in my studio recording instrument tracks for an album. The bass player had a horrible hum (I suspect the strings were ungrounded). Since the kid had a nipple ring, I was able to fix it by hooking a clip lead from his nipple to one of the screws on the guitar jack. So that might be an option...
As is often the case with young bands, the album project was abandoned when they broke up, due to realizing nobody in the band could (or wanted to) sing.

[Lostgallifreyan]

The firm Rane has two documents freely available that go into grounding details. It's worth finding those and keeping local copies. One shows wiring to adapt various connector types and standards for best results, and many of the diagrams show cables that can be bought ready made. The other is Sound System Interconnection, and goes into detail about how to manage safety grounds and signal grounds so their purposes do not conflict and end up in bad design. A lot of new gear is built according to the principles those documents set out, but older gear often isn't, so the adapter wiring detail may be what you need most.

Remember that old houses with noisy wiring in ring mains aren't really the problem, so long as you set up a star net to distribute power in your audio rig to avoid local hum loops. If these local grounds are good, they will exclude enough of whatever ambient noise remains.

[Hugh Robjohns]

So now im worrying that it's either the guitar, or even worse, bad wiring in my house.. Any advice?

Yes, it's the guitar.

There's very little difference, electrically, between a TV aerial and a guitar! They are almost perfectly designed to pick up and stray RF and EM fields in the local environment. And single-coil pickups are worst of all.

A good ground helps. Proper shielding of the control cavity helps (a lot, usually). Humbucking coils pickups help. Turning off (or staying well away from) things that radiate RF and strong EM fields helps — like computers, LED lighting, line-lump and wall-wart power supplies, anything with big mains transformers, etc etc

[ef37a]

I am willing to bet Vlandes a set of Ernie Balls for the guitar that the the bridge and hence the strings are not bonded to the jack earth. I am fairly certain Fenders did this in production but some people remove the link in the mistaken belief (IMO) that is makes the guitar safer. Lack of this bonding makes the strings 'float' even more adhering to Hugh's "TV Aerial" analogy.

If you have a Digital Multi-Meter (DMM) Check the resistance between the jack plate and the bridge. My bet is it will be infinite or very high. If you DON'T own a DMM then I strongly suggest you invest $20 or so on one. Anyone interested in recording,instruments and audio these days really should have a passing knowledge of circuit testing.

Lastly, do not have great expectations of a really quiet guitar 'system'. However, with care and decent gear and finding the hum 'nulls' in the room you can usually get acceptable results.

Dave.

[Wonks]

But if the noise reduces when the strings are touched, then that’s a very good indication that the trem system is grounded. Vlandes, you’ve been a bit contradictory on that. Can you be 100% clear if it gets better or worse when you touch the strings?

Vlandes, was the guitar new or used when you got it? If new, then there’s no reason for the trem system and strings not to be grounded. There should be a ground wire running from the back of the volume pot to the trem claw in the rear trem spring cavity.

You can also check that the volume and tone potentiometer nuts are tight and the jack socket nut is on tightly and not loose.

Does the hum almost stop with the pickup selector in the neck+middle and middle+bridge pickup position? The middle pickups on Squiers and Fenders are almost always reverse wound/reverse polarity these days, so those two positions should be near silent with regards to hum if there’s nothing wrong with the wiring and it’s just standard single coils picking up noise as normal.

[Wonks]

One thing guaranteed to cause hum no matter what you do, is if the signal and ground wires are crossed at the guitar’s output jack.

Very unlikely to come from the factory like that, but if it’s a used guitar, then the previous owner might have done some wiring mods.

And I don’t think we’ve mentioned the guitar lead yet. Have you tried another lead? Is it a good quality one or one that came with the guitar and has moulded jack plugs on each end? The cheap leads that often come with a guitar + amp starter kit or are thrown in by the guitar store can often have minimal shielding and themselves let in noise. The only good quality leads I know that have moulded plugs are the D’Addario/Planet Waves cables. There may be others, but they will almost certainly have a brand name on them, whilst the cheap Chinese leads are always anonymous.

If it’s a decent TS to TS lead, then fine, but it’s still worth checking that the soldered connections at each end are in good condition and you haven’t got a single strand of wire as the signal or ground connection.

[ef37a]

"But if the noise reduces when the strings are touched, then that’s a very good indication that the trem system is grounded. "

That has not been my experience Wonks.

Dave.

[Wonks]

Weird, because it is exactly mine.

[ef37a]

So I have set a Sontronics LDC in front of our HT-20* head driving a 12" Greenback. Mic into a MOTU M4.
Strat was the other side of the room and propped up against the sofa. Did a few seconds recording, al pots at max, bridge pup.
Then I took the rear plate off and cut the link wire from trem' plate to jack. Guitar exactly as before and recorded.

I ran the clips through Rick Mark Analyser...Both exacty the same ! 100Hz comes out at -36dB and 50Hz at -49dB. I then checked string continuity to jack. Still 8Ohms. Over ten years ago I had screened the guitar and sat the bridge on the screen!

So sorry, without dismantling the guitar I cannot check for the effect of floating strings but I have definitely had the problem before and it made the guitar more hummy without the bond AND it improved when you grabbed the strings.

Not really that surprising, hum issues can often be very counter-intuitive to diagnose and fix.

(Ooo! I have a bass...)

*For those that may not know? A 20W valve guitar amplifier, 2X EL34.

Dave.

[Wonks]

But the hum always improves when you touch grounded strings. The number of guitars I have with ungrounded strings is one, and that has EMGs fitted.

So without doing more experiments, the best we currently can say is that touching the strings and the hum reducing isn't 100% positive proof the strings are grounded, but touching the strings and the hum increasing indicates the strings aren't grounded.