Hum from amp, buzz from guitar

[hereonmars]

Howdy,

I know this isn't pedal-related, but this forum seems like a better place to ask this than anywhere else I currently lurk.

I am trying to find and diagnose the source of this awful buzz in my guitar. I have shielded the inside of the cavity with copper tape and ensured continuity with the ground. I have had my electrician fix a couple issues that the previous homeowners' DIY job didn't get right (missing ground for one, scary).

One thing everyone says is I need to buy a filtering power supply. I have not done that yet because a) I would be pissed if it didn't fix it and b) the sound of the amp when the guitar isn't plugged in only has that very low hum that I illustrate at the beginning of the video by turning my preamp up. I also know many of those units that purport to be filtering power are just rackmount power strips, which is what I have now.

Has anyone successfully chased down any sources of (what I think to be) RF interference in their house? How did you do it? This is driving me nuts!

One interesting thing: my Gibson with dirty fingers pickups which are only two-conductor does not have NEAR the amount of noise the LTD or my Schecter do, which both have coil split/tapping.

Your time and consideration are appreciated. -Mars

Edit: I apparently fat-fingered the save button before I finished typing. Sorry about that.

 

[jimilee]

I spent days chasing something like that, a while back. It was my computer monitor causing interference.

 

[JohnnyCreepy]

Just a reminder for myself too; worn or bad tubes leak heater current to cathode and it gives mains hum 50/60Hz and 100/120Hz. Don’t be me and chase hum from heater wiring, grounding and possibly cold solder joints BEFORE doing some preamp tube roll with known healthy tubes.

And be sure your cables are okay.

Then you can introduce yourself to more invasive things.

 

[giovanni]

Sorry I haven’t listened to the clip yet but I will. My previous apartment had atrocious hum and I bought a power conditioner. It did not help. One thing you can try is turning off large appliances like the refrigerator and see if that makes a difference. You can also try using different outlets attached to different breakers. I now have a music room with its own separate breaker and that made a huge difference, my single coil guitars are super quiet. P90s still a bit noisy but no comparison to the old place.

 

[hereonmars]

Just a reminder for myself too; worn or bad tubes leak heater current to cathode and it gives mains hum 50/60Hz and 100/120Hz. Don’t be me and chase hum from heater wiring, grounding and possibly cold solder joints BEFORE doing some preamp tube roll with known healthy tubes.

And be sure your cables are okay.

Then you can introduce yourself to more invasive things.

These are very low hours. However, I could try swapping the preamp tubes out if that's what you're referring to? There's no need to bias or anything if I recall.

I will say my other rig (all pedalboard) is noisy too but doesn't have the same low hum this one does.

 

[hereonmars]

Sorry I haven’t listened to the clip yet but I will. My previous apartment had atrocious hum and I bought a power conditioner. It did not help. One thing you can try is turning off large appliances like the refrigerator and see if that makes a difference. You can also try using different outlets attached to different breakers. I now have a music room with its own separate breaker and that made a huge difference, my single coil guitars are super quiet. P90s still a bit noisy but no comparison to the old place.

This is definitely on my list. I have the music room on a different breaker than others but there's other computers in here and stuff on the same one.

I would buy a different power supply that truly filters, even my electrician recommended it. But if I spent that money and it didn't address it I would be really irritated

 

[hereonmars]

I spent days chasing something like that, a while back. It was my computer monitor causing interference.

I'm gonna try again but I don't think that's whats causing this. Ugh

 

[jwin615]

First, make sure cables and your bridge ground are good.
Next, ground yourself and see if the noise goes away. If it does, it's your radiation(it happens, some pickups are more sensitive).
If you have another amp, see if you can repeat the issue on it. That will rule the amp out
From there, have to look at environmental noise.

To sus out environmental noise:
Put you guitar on a stand where you can hear the noise but it won't feedback(maybe mute the strings with something) and just start unplugging things and turning things off. Monitors, led and cfl bulbs, neon signs are terrible, dimmer switches, crappy cheap switching power supplies(hence, unplug, don't just turn off), etc.
Once you're standing in complete darkness, if you still hear the noise, you'll need to move to other rooms.
First. I would run an extension cord from a different circuit to the amp. Then, kill the breaker to the previous circuit.
Assuming it's the same result, meaning you've ruled out anything in the room with the amp, restore the original configuration and keep killing breakers until it stops. Once it stops, turn all the breakers back on except the one causing the problem. Verify the noise is still gone. You'll then have to find the source on the problem breaker. Turn off/unplug...

 

[JohnnyCreepy]

These are very low hours. However, I could try swapping the preamp tubes out if that's what you're referring to? There's no need to bias or anything if I recall.

Yup, preamp tubes for sure if the hum appears when turning more gain/volume up with nothing in input. No need to bias. I made a long trip on doing several things before realizing I had two bad preamp tubes in my tube collection which I thought are good.

Also isolating problem to the preamp side is done removing one tube at time from input(V1) towards phase inverter tube (V3 or else. If hum disappears for example removing V2, problem is that tube or circuitry betweem removed tube and input jack.

 

[JTEX]

@jwin615's troubleshooting checklist is very thorough. I'd just add that all humbuckers are definitely not equally good at humbucking, and NO amount of copper shielding the cavity will make any difference if the noise source is an electromagnetic field (such as leakage from a nearby power transformer).

 

[Gordo]

My bench light at the music store I work at is the culprit for me. Was fine for the 20+ years I've had it in 3 different houses but when I moved it to the store: Bzzzzz. I've resigned myself to just turning it off when I test guitars/amps/pedals so it's a minor inconvenience.

 

[hereonmars]

First, make sure cables and your bridge ground are good.
Next, ground yourself and see if the noise goes away. If it does, it's your radiation(it happens, some pickups are more sensitive).
If you have another amp, see if you can repeat the issue on it. That will rule the amp out
From there, have to look at environmental noise.

To sus out environmental noise:
Put you guitar on a stand where you can hear the noise but it won't feedback(maybe mute the strings with something) and just start unplugging things and turning things off. Monitors, led and cfl bulbs, neon signs are terrible, dimmer switches, crappy cheap switching power supplies(hence, unplug, don't just turn off), etc.
Once you're standing in complete darkness, if you still hear the noise, you'll need to move to other rooms.
First. I would run an extension cord from a different circuit to the amp. Then, kill the breaker to the previous circuit.
Assuming it's the same result, meaning you've ruled out anything in the room with the amp, restore the original configuration and keep killing breakers until it stops. Once it stops, turn all the breakers back on except the one causing the problem. Verify the noise is still gone. You'll then have to find the source on the problem breaker. Turn off/unplug...

thank you, I have done almost everything I could while having the amp plugged into the current room. Only thing to do is power it from another breaker and shut off this entire room. I even shut off all the other breakers in the house (one at a time) and it didn't do anything.

I am thinking it might just be from something I can't control, unfortunately.

 

[hereonmars]

@jwin615's troubleshooting checklist is very thorough. I'd just add that all humbuckers are definitely not equally good at humbucking, and NO amount of copper shielding the cavity will make any difference if the noise source is an electromagnetic field (such as leakage from a nearby power transformer).

I'm afraid this might be the case. I may just do what he does in this video and walk around with my amp and guitar and see if it gets better/worse

 

[GAStan]

Have you tried the guitar & amp at an entirely different location?

 

[RetiredUnit1]

My hum was the outside fuse box on the other side of the wall. If you rotate your body 360 and hear a quiet spot, then you're guitar is acting as an antenna. I bought an RF dectector on eBay and that's how I found the really noisy spot was the fuse box. Moved everything to the other side of the room and it was gone.

I had the same thing up in the front of the house, ended up being the doorbell transformer.....

 

[owlexifry]

how far do you live from one of these?

 

[hereonmars]

Have you tried the guitar & amp at an entirely different location?

Yes, it definitely doesn't have the same noise.

 

[hereonmars]

My hum was the outside fuse box on the other side of the wall. If you rotate your body 360 and hear a quiet spot, then you're guitar is acting as an antenna. I bought an RF dectector on eBay and that's how I found the really noisy spot was the fuse box. Moved everything to the other side of the room and it was gone.

I had the same thing up in the front of the house, ended up being the doorbell transformer.....

I have a large box behind my back patio that belongs to the utility company, which is my number one suspect.

 

[hereonmars]

View attachment 91004
how far do you live from one of these?

Not sure but gonna start looking. Mentioned in another reply I also have a large box of some sort behind my property that belongs to the utility company.

 

[JohnnyCreepy]

There’s really good info shared here, but I’m still strongly suggesting excluding preamp tube problems before going inside amp chassis, shielding guitar, suspecting household AC problems etc. So did you already check does hum disappear when removing preamp tubes one at the time?

Remove input tube first, flick amp on and off from standy and adjust volume/gain/master. Listen. If hum is still there, flick amp off and proceed for removing the second preamp tube. Listen, turn amp off, remove tube and so on. What happens when phase inverter is removed?