Excessive amp buzz

AllthegearNoidea

I have an issue where the buzz through my amp is horrendous when turned up. It is worse through my Les Paul than strat and unbearable when I use pedals. I have tried feeding my rig through a ups and a mains conditioner. Neither make a difference. I am thinking I have a ground issue with my mains supply which is a PME type combined neutral and earth. I have been told to check for voltage between neutral and earth and this measures at 0.04vac which seems inconsequential. I have tried different cables and pedals. I have tried the amp elsewhere and there seems to be no significant buzz. I am considering an earth spike connected to earth on the socket I use for my rig. Any thoughts appreciated

Marshall 2061x, Les Paul Greg Martin reissue and Fender custom shop strat.

ICBM

If there's no buzz elsewhere the problem is either noise on your mains supply or something else at that location - are there any computers or other switch-mode power supplies nearby? If the amount of buzz depends on the signal strength going into the amp I'm more inclined to think it's something being picked up by the guitar than the amp.

Nomad

Elsewhere in the same room or building? On a different ring in the mains?

AllthegearNoidea

Hi thank for speedy reply. I have two PCs and an a/c unit closes to the amp but the buzz is only present when the guitar is plugged in and within 7' of the amp. I forgot to mention this amp is in a log cabin in my garden connected by SWA to the house. I have shutdown everything in the cabin and the house and the noise persists. I tend to agree this is mains noise but can't think of a solution.

AllthegearNoidea

Noise is also present in main house.

ecc83

I would not normally suggest this but since you have checked the neutral to earth voltage (where?) I don't think you are the type to kill yourself, so.

Check the resistance from a 13A outlet earth pin to a KNOWN good earth. A cold water pipe as it comes from the road is best. The idea is to make sure your mains circuits are actually earthed. Best to have a resistance less than 1 Ohm but since this is hard to measure accurately on most DMMs a bit more won't hurt (subtract out any test cabling) .

If you are earthed ok then you might be in a "field" from a sub station or overhead HT?

Once in a while I see threads on other forums about hum and nothing seems to fix it.

DO NOT play around connecting random earth spikes into the Company supply!

Dave.

AllthegearNoidea

ecc83;377649" said:

I would not normally suggest this but since you have checked the neutral to earth voltage (where?) I don't think you are the type to kill yourself, so.Check the resistance from a 13A outlet earth pin to a KNOWN good earth. A cold water pipe as it comes from the road is best. The idea is to make sure your mains circuits are actually earthed. Best to have a resistance less than 1 Ohm but since this is hard to measure accurately on most DMMs a bit more won't hurt (subtract out any test cabling) . If you are earthed ok then you might be in a "field" from a sub station or overhead HT? Once in a while I see threads on other forums about hum and nothing seems to fix it. DO NOT play around connecting random earth spikes into the Company supply!

Dave.

Mains water pipe is plastic unfortunately so I would have to make my own earth as everything else in the house is bonded to the combined earth and neutral supplying the house. As you have guessed I have some experience with voltage testing etc. I removed a socket from the wall to measure between Earth and neutral and could hammer an earth spike in to the ground and measure resistance to the live on the socket upplying the amp. Would this be a suitable earth?

Keefy

Do you still get the noise when you turn the volume right down on your guitar? What about with nothing plugged into the amp?

ICBM

AllthegearNoidea said:

Hi thank for speedy reply. I have two PCs and an a/c unit closes to the amp but the buzz is only present when the guitar is plugged in and within 7' of the amp. I forgot to mention this amp is in a log cabin in my garden connected by SWA to the house. I have shutdown everything in the cabin and the house and the noise persists. I tend to agree this is mains noise but can't think of a solution.

If moving the guitar further away from the amp cures it, the problem is noise being generated by the amp being directly picked up by the guitar and then re-amplified. How and why the amp is generating noise is the next problem...

Where is your power conditioner - in the cabin, or in the house?

Have you tried a different amp in the cabin?

AllthegearNoidea

The amp hisses only slightly with nothing plugged in.

The buzz decreases as I lower the guitar volume when plugged in until when the volume is off the noise is a slight hiss as if nothing is plugged.

All amps do it so I think it is a 'house' issue

Mains conditioner was in the form of an extension lead type plugged in directly before the amp. Same with the UPS

It seems to be amplified by the guitar and the power of the pickups.

Closest I can get to describing it is the noise from a fluorescent light fitting but I thought I had nothing in the house to generate that type of noise however I have just halved the amount of noise by turning off the power brick that powers an Xbox one!!

Still have the fluorescent tube noise but greatly reduced. 

If I power the amp through an UPS and touch the pick up cover the noise stops completely with the guitar volume at 10. If I power the guitar from the mains and touch the pickup cover the noise remains the same. Is this an earthing issue?

Thanks for your help.

AllthegearNoidea

I have found another power supply brick for a fax machine adding to the noise. Many thanks for all suggestions so far

ICBM

AllthegearNoidea said:

The amp hisses only slightly with nothing plugged in.

The buzz decreases as I lower the guitar volume when plugged in until when the volume is off the noise is a slight hiss as if nothing is plugged.

In that case it is definitely radiated noise being picked up by the guitar pickups, not an earthing issue (to the amp, at least).

AllthegearNoidea said:

All amps do it so I think it is a 'house' issue

Yes.

AllthegearNoidea said:

Closest I can get to describing it is the noise from a fluorescent light fitting but I thought I had nothing in the house to generate that type of noise however I have just halved the amount of noise by turning off the power brick that powers an Xbox one!!

It is definitely this kind of environmental noise. The only question is whether it's getting to the guitar directly ('airwaves') or travelling via the mains cabling to the cabin.

I would expect that if it's via the cabling unless the cabin is *very* close to the house, particularly if moving away from the amp helps - I think it's most likely that the noise is being radiated from the amp's power transformer winding having got there via the supply. You may be able to fit a noise suppressor on the supply or the amp.

AllthegearNoidea said:

If I power the amp through an UPS and touch the pick up cover the noise stops completely with the guitar volume at 10. If I power the guitar from the mains and touch the pickup cover the noise remains the same. Is this an earthing issue?

Does touching the guitar strings not stop it? If not, and touching the pickup cover does, then the strings are not grounded§… they should be. (Not technically the same as "earthing" even though the terms are often used interchangeably.)

ThePrettyDamned

If it makes you feel better, every night (at different times, though), playing through an amp in my house leads to great noise, and it's directional from the guitar - in other words, I can reduce it by facing a different direction.

Never figured out what it is, I gave up. 

ICBM

ThePrettyDamned said:

If it makes you feel better, every night (at different times, though), playing through an amp in my house leads to great noise, and it's directional from the guitar - in other words, I can reduce it by facing a different direction.

Never figured out what it is, I gave up. 

You will usually find that the source of the buzz is directly in line with the axis of the pickup coil when you can find that 'null point'.

Chances are it's someone in the house - or the next house, if you live in a block - using something which emits the noise.

ecc83

Try turning the amp on its side.

Dave.

DartmoorHedgehog

ecc83 said:

Try turning the amp on its side.

Dave.

Or play lying down - even if it does nothing for the noise you'll be more relaxed and it won't wind you up so much...

ecc83

DartmoorHedgehog said:

ecc83 said:

Try turning the amp on its side.

Dave.

Or play lying down - even if it does nothing for the noise you'll be more relaxed and it won't wind you up so much...

I wasn't joking! This puts the transformer radiation into a different plane and could well null out the hum.

Anyone who has built a valve amp from scratch will understand the process.

Dave.

DartmoorHedgehog

ecc83 said:

I wasn't joking! This puts the transformer radiation into a different plane and could well null out the hum.

I know... was just being silly... sorry 

(but it would have the same effect)