Understanding noise

[Nice F Holes]

I've got a little noise in my system that I'm trying to understand and mitigate if possible. Guitar is SE Hollowbody II Piezo, using MAG output to Effectrode Blackbird preamp, and headphones from the preamp. I believe I have 60hz 'hum' as well as a 'buzz'. Both noises go away when I roll down the volume on the guitar, and both are louder with higher gain. The buzz goes away when I touch anything that's metal: the strings, the plugs/jacks, a footswitch button on the preamp, etc.

I have a tuner, overdrive, and cab sim at the moment as well. I removed everything but the pre from the chain and still had the noise, and if I remove the pre and use everything else, it's quiet. IDK if that's because the problem is the pre, or if it's just amplifying the noise (4 stage cascading gain). The overdrive is new so I haven't tried high gain direct to the cab sim yet.

Some amount of noise is 'normal' correct? Or is it realistic to expect a completely quiet system? Any tips to help diagnose?

Thanks!

Edited to add that I'm using a power strip that has a couple USB ports on it. Tonight I'll try with the pre straight into the wall and in different locations of the house.

 

[CandidPicker]

Try using a DI box with the ground lift button switched in. The ground lift may help with the ambient noise. (Can't verify, since my rig doesn't have the hum initially, but a Radial Pro DI is designed to do what you seek.)

I prefer a DI box to help smooth out the frequency curve. The ground lift and phase switch is a nice bonus in case of noise/phase issues.

 

[Aahzz]

Normally if the buzz goes away when touching metal it's a grounding issue - you may need to check the ground wire soldered to the bridge in the guitar.

 

[Stephen J.]

First thing that came to my mind when I read the title was Foo Fighters.

 

[andy474x]

I’ve had the same issue with one of my guitars - S2 Custom 22 Semi, lots of buzz and manifested as a grounding issue that was reduced when touching the metal parts of the guitar. For the life of me, I couldn’t figure out why this guitar was so buzzy. I checked the wiring with a multimeter to confirm good grounding on all electrical and parts, etc. What it was, was sitting right in front of me when I opened the control cavity - it was never shielded. Most of my other guitars have shielding paint in the control cavity, this one didn’t, and the electronic components were picking up all kinds of EMI. Just to see if my hunch was correct, I shielded the control cavity with aluminum foil, and sure enough, quiet as a church mouse now. I realize the S2’s make their price point via omitting some of the finest things, but IMO shielding isn’t something that can be compromised, so I’m slightly disappointed there was a corner cut there, on an otherwise excellent guitar.

Anyways, that could be your issue. Especially on a hollow body, and from what I can see, those don’t have a true control cavity, the electronics are probably installed through the F-hole, there isn’t really a defined area to shield. Maybe you could put shielding paint on the front and back laminates (inside the body), and that may help some, but a bit of ground related buzz might just be the reality with a guitar like that.

 

[garrettb]

Since the buzz goes away when you touch the string path, it means the guitar is properly grounded. Electric guitar circuits are designed to use you as the ground point for canceling out interference. This is why guitars always have a ground wire connected to the bridge.

Some buzz is normal. The wire, pots, etc. are antennae for noise. You can reduce it greatly with shielding, but that's obviously a difficult proposition on a Hollowbody.

You should only have 60 cycle hum if you're using single coils, or you can get a bit when using unbalanced humbuckers, too.

The preamp is going to amplify everything, including noise.

This is all punishment for our insistence on relying on 80+ year old electronic technology.

Lack of shielding isn't necessarily cost cutting. Core guitars have zero shielding.

 

[Nice F Holes]

Anyways, that could be your issue. Especially on a hollow body, and from what I can see, those don’t have a true control cavity, the electronics are probably installed through the F-hole, there isn’t really a defined area to shield. Maybe you could put shielding paint on the front and back laminates (inside the body), and that may help some, but a bit of ground related buzz might just be the reality with a guitar like that.

I was wondering about that too. From the SE Hollowbody Standard thread it looks like they used shielded wiring so hopefully that would suffice. I'm definitely not taking this guitar apart until I've got another one to play though, so hopefully it's something else. Is there a way to confirm or rule out a shielding issue?

 

[Nice F Holes]

It sounds just like this guys guitar (starting at 3:36).

 

[docteurseb]

Every single guitar I have that doesn't have its cavity shielded (meaning PRS and Gibson) does that, the others don't.

 

[Rhythmisking]

Since the buzz goes away when you touch the string path, it means the guitar is properly grounded.

I think you mean ISN'T properly grounded, no?

 

[Nice F Holes]

I don’t know WTF happened but I can’t seem to get a clean tone anymore. Playing through just the preamp, or just the cab sim, the clean tones have a bit of crunch/fuzz to them. Now I’m a bit frustrated.

 

[Nice F Holes]

I checked continuity between the 3 pots, 2 jacks, switch and bridge and all are grounded. The jack nuts are apparently isolated. I guess because they’re switching type jacks.

 

[garrettb]

I think you mean ISN'T properly grounded, no?

No.

A ground problem would be buzz that doesn't go away or gets louder when you touch the strings.

 

[Rhythmisking]

No.

A ground problem would be buzz that doesn't go away or gets louder when you touch the strings.

Yes, but if the bridge ground wire isn't attached or making contact properly, there will be buzz that goes away when you touch the strings or bridge...

 

[garrettb]

Yes, but if the bridge ground wire isn't attached or making contact properly, there will be buzz that goes away when you touch the strings or bridge...

No.

If the bridge ground wire is not connected, the buzz will NOT go away when you touch the strings.

The purpose of the bridge ground wire is so the buzz DOES go away if you touch the bridge, strings, or anything else in the path like tuners, trem springs...

 

[Rhythmisking]

Hmm...so the guitars I have that don't have any buzz at all whether I'm touching the strings or not are magical?

 

[Nice F Holes]

No buzz is obviously ideal. If there is some buzz, usually touching exposed metal, like a connected plug, will quiet it down. If you touch the strings and it gets quiet then you know the strings and bridge are connected to the other exposed metal.

Hmm...so the guitars I have that don't have any buzz at all whether I'm touching the strings or not are magical?

 

[László]

I have a tuner, overdrive, and cab sim at the moment as well. I removed everything but the pre from the chain and still had the noise, and if I remove the pre and use everything else, it's quiet. IDK if that's because the problem is the pre, or if it's just amplifying the noise (4 stage cascading gain). The overdrive is new so I haven't tried high gain direct to the cab sim yet.

Some amount of noise is 'normal' correct? Or is it realistic to expect a completely quiet system? Any tips to help diagnose?

I have a perfectly quiet system that I've spent a lot of time getting that way. It took me about ten years of studio ownership back in the analog days to discover how to deal with ground loops with my recording gear, and during that time I had a studio tech with an oscilloscope to help out. Ground loops can be difficult to track down, but not so difficult to track down in a guitar rig.

If pickups are near electromagnetic or radio frequency interference (EMI and RFI), like dimmers, certain light fixtures, or monitors, they will buzz, but that doesn't sound like what you're describing, because you mention 60 Hz hum, which usually isn't part of pickup buzz. I suspect a ground loop, though it could be some other issue.

There's a lot of information on the web about chasing down ground loops, and most of it is useless. But there is some good stuff.

Generally, if buzz accompanied by 60Hz hum goes away when you remove a single piece of gear, you most likely have a ground loop related to that gear. That means that the signal is seeing more than one path to ground. Also, most buzzes get worse when there's a ground loop in the system.

There are a lot of ways to prevent or eliminate ground loops. The first thing (if you have pedals, guitar preamps, etc) is to consider removing any wall warts, or crappy daisy chained power supplies, or power supplies that aren't isolated. Power all pedals with a good, isolated power supply. Granted, sometimes wall warts are necessary if you can't power a piece of gear with an isolated supply, but most pedals can be powered with modern power supplies. There are a number of excellent power supplies for pedals with isolated outlets, the best known being the Voodoo Labs, which is what I use. However, Strymon makes some good ones, Cioks are good, etc.

On another front not having much to do with ground loops per se, wall warts are notorious hum generators. Keep any power strips with them well away from your other pedals and cables. Also, some cables pick up hum because they're not properly shielded, or the shielding has come apart from being stepped on, or other mechanical causes, normal wear and tear, etc. Replace faulty cables.

If you're using two amps, or plugging into an amp and a recording interface, etc, and you're getting hum because the two pieces of gear are causing ground loops, you can use an isolation transformer, such as the Lehle P-Split, to lift one of the signal grounds. The Lehle is one of the few such devices that don't suck tone.

Do NOT use a "ground lift adapter" to lift the ground on one of the amps except to test for long enough to discover if that's the problem. Dangerous, not recommended!

Finally, some gear is simply not properly designed with respect to grounding. That's a sad fact of life in the audio world. So while it's unlikely, if nothing you try works, consider trying a different piece of gear.

 

[Nice F Holes]

Last night I plugged in just the preamp and a cable, no guitar. Holding the cable off the ground, not touching metal, I still had buzz that got better if I touched metal. It was repeatable with 3 different cables. I also tried with extension and went outside, no help. Plugging in just a 1/4” jack with no cable made no noise.

Is that normal?

Then I plugged in the guitar and it was actually better.

The cables are all old-ish and not necessarily high quality. They were marketed as such but, you know how that goes. My main cable is Conquest USA1 or something like that. Last night I received bulk to make new quality cables so I’ll do that and test tonight.

The preamp is all tube at 300v but runs off a 2-prong Ac/Dc adapter, sending 1a at 12v to the pre. So it’s not grounded to the house electrical system.

 

[garrettb]

Hmm...so the guitars I have that don't have any buzz at all whether I'm touching the strings or not are magical?

No.

They are properly grounded and also well shielded. Or there just isn't enough EMI to make significant buzz.