Ground Question

[Chris F]

I'm having a problem in my home studio with what I'm assuming is a Ground issue....when I plug in a bass or guitar to any amp, the amp buzzes like crazy the second the player takes his hands off of the strings, no matter which position the "ground lift" switch on the amp is set to. However, when I take the same guitar/bass and amp to another location, this buzzing is not an issue. BTW, this affects only the amplifiers in the room, and has not (as yet, anyway) affected the recording gear.

Does anybody have any ideas about what I might be dealing with here, and what the possible solutions to try might be?

Thanks,

Chris

 

[Rochey]

Try switching off your monitor...

CRT monitors (STandard big ones ) actually emit a magnetic field which induces an electric signal in single coil guitar pickups (especially cheap strats )

Normally, before I hit the record button, I try to switch off the monitors, just to clean the sound a bit. Sometimes it works, sometimes it doesnt.

Try doing a search here, there must be athread where it's been discussed.

cheers

R

 

[Rochey]

Try this thread, and look for knightfly's reply...

he's already written what I couldn't be bothered with writing


https://homerecording.com/bbs/showthread.php?s=&threadid=60016&highlight=hum+guitar+monitor

 

[Chris F]

Rochey,

Thanks, but I don't think that's the problem...I use an LCD monitor with my G4, and the hum persists even when I'm not recording and the computer itself is turned off. My wife has a 19" CRT monitor in the next room, but I doubt that could be causing the problem. Or could it?

I should mention that my studio is in a very old house, although the wiring was redone sometime in the 70's. Are there any tests I might be able to run to check the ground on that circuit? Or any products out there designed to "clean" power that seems "dirty"?

 

[Sonixx]

...when I take the same guitar/bass and amp to another location, this buzzing is not an issue...

when you say another location what do you mean... another in the same house... another house... what?

have you tried another circuit in this house?

the outlets are two prong or three?

do you have an outlet tester? if not, go to Home Depot or Lowes and buy one or borrow one if available.

is this room above ground or a basement with a concrete floor?

 

[Track Rat]

CRTs, TVs (even in other rooms), dimmer switchs (especially in a halogen floor lamp we have here in the house) are all notorious noise makers. If i'm downstairs in the studio and my girlfriend turns on the floor lamp in question upstairs in our bedroom my Strat or Tele lights up like a pinball machine, and my studio is on a dedicated circuit with its own subpanel/breakers.
Also how and where things are plugged in to power and audio gear, it's easy to set up a ground loop. For example, say you have a bass amp on one side of the room and it's plugged into the wall outlet nearest to it. Your recording gear is on the other side of the room and gets its AC from a different source. If you were to take a direct out from the bass amp to your recorder now you're set up for a ground loop.

 

[Sonixx]

that's good food for thought... Track Rat

does moving around in the room make significant differences in Buzzing?

 

[Chris F]

Re: Re: Ground Question

when you say another location what do you mean... another in the same house... another house... what?

I meant when I take the same gear out on gigs in clubs or auditoriums, I don't have the same problem, and neither does my guitarist. When we record here, he has to take a piece of wire from his cable and run it up to one of the strings between the bridge and tailpiece of his archtop to make sure the sound stops. On gigs, he doesn't have to do this.

have you tried another circuit in this house?

I feel kind of stupid about this, but actually, I haven't. I'll do that soon and report back.

the outlets are two prong or three?

Three

do you have an outlet tester? if not, go to Home Depot or Lowes and buy one or borrow one if available.

I don't have one, but if it would help to diagnose the problem, I'll get one. About how much do they run, and what specifically do they test?

is this room above ground or a basement with a concrete floor?

It's on the first floor, with a wood floor and some area rugs. Thanks for the suggestions, I'll try some of those out!

 

[Chris F]

CRTs, TVs (even in other rooms), dimmer switchs (especially in a halogen floor lamp we have here in the house) are all notorious noise makers. If i'm downstairs in the studio and my girlfriend turns on the floor lamp in question upstairs in our bedroom my Strat or Tele lights up like a pinball machine, and my studio is on a dedicated circuit with its own subpanel/breakers.
Also how and where things are plugged in to power and audio gear, it's easy to set up a ground loop. For example, say you have a bass amp on one side of the room and it's plugged into the wall outlet nearest to it. Your recording gear is on the other side of the room and gets its AC from a different source. If you were to take a direct out from the bass amp to your recorder now you're set up for a ground loop.

The CRT is in the next room, and may well be on the same circuit...I'm not sure. I got rid of all the dimmers, and the problem persisted. If I can search out any info on ground loops, I'll do so and see if that could be involved as well, thanks.

 

[Sonixx]

if all you're doing is connecting directly into the amp from the Guitar and the amp is only connected to power, then you won't have a ground loop. if you're using a Direct Out into the Board or something like that, then you may have a ground loop, especially if the board and amp are on different circuits. if this is the case, then you'll need to use a DI Box or use power from the same outlet (best) or another outlet but same circuit.

does moving around make a difference?

what kind of pickups... single coil... humbucker... tried other guitars...

how about fluorescent lighting

 

[Chris F]

if all you're doing is connecting directly into the amp from the Guitar and the amp is only connected to power, then you won't have a ground loop. if you're using a Direct Out into the Board or something like that, then you may have a ground loop, especially if the board and amp are on different circuits. if this is the case, then you'll need to use a DI Box or use power from the same outlet (best) or another outlet but same circuit.

does moving around make a difference?

A little bit, but the problem still persists

what kind of pickups... single coil... humbucker... tried other guitars...

My Double Bass has piezo pickups on it, and they don't hum (because they're not magnetic, I'm guessing). My electric bass is a Ken Smith BSR6P...kind of an expensive boutique handmade bass with double coil Smith soapbar pickups on it. The guitar my guitarist friend and recording partner in crime uses is a Buscarino archtop...again, a handmade instrument. I'm not sure what kind of pickups it has, but I'm sure it's high end, since the damn thing is worth more than my car.

As far as other guitars and basses, yes; my students bring a variety of instruments in (I teach in my studio), and they all hum. The amps used vary from an SWR Baby Blue and Acoustic Image Clarus all the way down to Polytone.

how about fluorescent lighting

Nope, no flourescent lighting. I installed Halogen track lights a while back, then got rid of the dimmer for them, which buzzed like a mother****er, so now they're on a simple on/off circuit. The buzzing still persists even when all the lights are off, so I know they aren't the problem.

 

[Sonixx]

Open every breaker in the box except this rooms outlets. what then.

if still buzzing, try another circuit in the house and do the same.

do you live under or near a power transmission line?

is the problem worse at certain times of the day?

 

[knightfly]

How many pieces of gear in your studio have "wall warts" or "line lumps" for power transformers? Now, are there any audio lines that run within 3-4 feet of any of those transformers? If so, try either moving wires away from the transformers or unplugging any unnecessary transformers.

I once made the mistake of plugging a wall wart into the auxiliary AC outlet in the rear of a power amp, past which the two 24" shielded phone cables ran to the power amp input. If the resultant hum had been any worse, I would have thought I'd plugged the speaker directly into the AC outlet... Ever since then, I've made sure to banish ALL transformers to their own little world, as far away from all the other "children" as their cords will allow.

Basically, you need to turn off EVERYTHING in your studio, try the amp/guitar(s) in question, and if no hum, turn on one thing. Repeat the tests until you turn on something and it hums.

BTW, we ARE talking about 60 hZ, are we not? sounds real close to the second lowest C on a piano. I know this sounds like a silly question, but people have called all sorts of noises "hum", just checking -

Did the people who built these "boutique" instruments know about shielding/grounding? Are the control cavities lined with copper foil, and are all the pots connected together at the cases, with a common wire?

Most anything else that I could think of has already been mentioned. The outlet tester mentioned runs about $10-$15 at home centers - it comes with directions, you plug it in and certain lights will light up - the directions tell you what's wrong in each case. That's the first thing I plug in when setting up for a gig - you wouldn't believe the bizarre stuff club owners think passes for power... Steve

 

[Chris F]

How many pieces of gear in your studio have "wall warts" or "line lumps" for power transformers? Now, are there any audio lines that run within 3-4 feet of any of those transformers? If so, try either moving wires away from the transformers or unplugging any unnecessary transformers.

Actually, I don't think I have any of them left at all.

I once made the mistake of plugging a wall wart into the auxiliary AC outlet in the rear of a power amp, past which the two 24" shielded phone cables ran to the power amp input. If the resultant hum had been any worse, I would have thought I'd plugged the speaker directly into the AC outlet... Ever since then, I've made sure to banish ALL transformers to their own little world, as far away from all the other "children" as their cords will allow.

Basically, you need to turn off EVERYTHING in your studio, try the amp/guitar(s) in question, and if no hum, turn on one thing. Repeat the tests until you turn on something and it hums.

This would include stuff in all other rooms that are on the same circuit, right? Will do.

BTW, we ARE talking about 60 hZ, are we not? sounds real close to the second lowest C on a piano. I know this sounds like a silly question, but people have called all sorts of noises "hum", just checking -

I'll check this as well.

Did the people who built these "boutique" instruments know about shielding/grounding? Are the control cavities lined with copper foil, and are all the pots connected together at the cases, with a common wire?

The Smith is incredibly well shielded - even though it still buzzes when I'm not touching the strings, it does so in a much quieter manner than any other instrument in the room with a magnetic pickup. The Buscarino I can't tell you about, since it's not mine and I haven't taken it apart.

Most anything else that I could think of has already been mentioned. The outlet tester mentioned runs about $10-$15 at home centers - it comes with directions, you plug it in and certain lights will light up - the directions tell you what's wrong in each case. That's the first thing I plug in when setting up for a gig - you wouldn't believe the bizarre stuff club owners think passes for power... Steve

At that price, I'll check into that as soon as I get out to buy one. Thanks for all the suggestions.