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Why Is My Amp Buzzing So Much


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My amp never used to buzz and hum this much. Then I moved and now it's awful. It's a Marshall microstack - 15w, solid state.

Symptoms are (all on overdrive selected and gain half way):

no guitar lead plugged in - no hum

guitar lead plugged, me not touching anything - lots of hum

guitar lead plugged, me holding other end (not touching tip) near to amp - no hum

guitar lead plugged, me holding other end (not touching tip) far from amp - lots of hum

epi lp standard plugged in - lots of hum on all 3 pickup positions

my first build plugged in on either bridge hb or neck hb only - lots of hum. in the middle (both pups) - no hum.

And it's the last bit that really confuses me.

Anyway, I know nothing about this stuff, so any thoughts? would something like this: http://guitars.musiciansfriend.com/product...ator?sku=150452 help?

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Man, I know next to nothing about this issue, but one thing I have found is if the outlet you are plugging into is not properly grounded, and having a three hole receptical is no guaranty that the outlet is grounded, then your (or at least my) amp will buzz. Odds are it's a ground issue. Have you tried other outlets or another building to see if you get the same thing?

SR

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  • 1 year later...
  • 3 months later...

Not sure if you have sorted it yet but as others have said sounds a bit like an earthing problem as you are grounding it through the lead.

simple things first - move it back where it was. does it go quiet again?

move it towards certain areas of the room. does it get worse at certain places.

You could try ferrite rings on the leads http://www.ehow.co.uk/how_7636890_use-ferrite-ring.html they are pretty cheap http://www.maplin.co.uk/ferrite-rings-29788?c=maplin&utm_source=gcs&utm_medium=gcs_search&utm_campaign=QT26D&utm_content=Amateur+Radio+Accessories

just loop them through the cable. These are the same principle as the plastic lumps that are on computer cables/usb cables etc. They just remove interference.

My peavey tnt150 hums sometimes and i give it a thump on the front and it quiets down. so there must be a loose connection somewhere.

If the above doesn't work

If oyu are realatively happy with electrics unplug it (leave it for ages as capacitors hold charge) and open it up and have a look for dry joints (little cracks in the solder) where capacitors are soldered to the board and check any earth straps to the frame.

Only do this if you are really happy with electrics - have it turned on and with an electrical screwdriver (insulated all the way down) gently tap the capacitors and listen for a change in the hum. You can sometimes find a dry joint this way. You can also get freeze spray to cool capacitors which often highlights the problem one as they work better when cold. My hi-fi amp had a failing transistor that worked fine when hit with freeze spray.

Seriously only open it up if you 100% happy to do this, don't need you getting electrocuted. not sure what country you are in but in the UK modern fuse boxes have RCBs which should stop you getting properly shocked. If you don't have one then you can get plug in ones that do the same, which could be a worthwhile investment if gigging anyway for safety.

hth

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