Humming from my Amp, help

[Stevepage]

Hey guys. Since I got the combo I've been on and off with the speakers. I think they will have to get changed to something else. Something with more balls but

There's this annoying humming coming from the amp. You don't really notice it when playing with a band but when I'm at home jamming, you can hear this annoying humming. It becomes louder when I use the FX loop, When I bypass the FX Loop it's quieter, but you can still hear it.

What could be causing this humming? The give you an idea of what it sounds like, it sounds like I've not plugged my lead into my guitar and picking up white noise.

[maverickf1jockey]

Are you using a high-gain sound?

It could be that the amp is picking up interference from various electronic appliances around your house.
These are, likely, not present at the shows and practices so that may be why you are not experiencing it in that situation.

I'd suggest going around meticulously turning off televisions (especially CRTs), computer monitors, computers and Hi-Fi equipment.

[Stevepage]

I did that, turned off my TV and it still persists.

[38thBeatle]

I was going to suggest mains hum too but you seem to have eliminated that. I had something similar at a venue recently and found that one of my pedals was affecting the amount of hum. I shoved a battery in it rather than use the transformer and that improved matters. I ended up running a cable from a separate mains source and that improved things but I have not had the problem to any extent before or since.

[CUBE]

if its a tube amp.. well they hum a bit .

mine was getting annoying,, it was bad caps in the output .

[Roobubba]

I wouldn't say you've eliminated the mains interference possibility yet. With my system, I ended up getting a power conditioner (exactly like this but from somewhere else a bit cheaper! clickeh) and that helped a huge amount. Also, I now use ClearTone cables from Award Session, and these are infinitely better than the planet waves I used to use. Oh, they're cheap, too.
I also shielded the innards of my guitar with foil, and padded behind the humbucker with foam.
The final thing I did was to get an ISP decimator ProRackG, but that's a little more expensive!

Hope some of the early suggestions help.

[WezV]

i would second 38ths suggestions of looking for any pedals that may be picking up more noise... i noticed a weird noise the other week and when i turned the volume up full to try and destinguish it it turned out my Dr Q was picking up radio transmissions :o

other than that its a process of elimination.. if you can it helps to try out different guitars and amps as well as leads and pedals

then it sometimes comes down to amp design.. some amps simply make more noise than others

[Fikealox]

Think about getting an ISP G-string noise gate (or the Pro rack G). It is, in my opinion, the best noise reduction around. It has two circuits, one for stuff coming into the input of the amp, and another for the FX loop. If it's a problem in your pre-amp or in your effects, cables, or guitar, it will definitely help. If not... well, it won't hurt, and it'll definitely help you narrow down the source of the hum by isolating different parts of your rig.

Also, even if you don't have spare cables lying around, try swapping the order of your cables in your effects chain, and listen for changes in the hum.

[Stevepage]

The only pedal I'm running with it is an overdrive pedal, even when turned off (it has a true bypass) i still get hum. Even when the TV is off it's still there. I've tried every guitar I've got and every lead and it's still there, even when nothings plugged in.

I've got a feeling the original owner (not Crazy Joe) had it modified with some kind of 'power soak'. There's a switch on the back with a knob, when you flick the switch the volume drops and you can adjust the volume via the knob. the hum is louder when the power soak is turned on.

By the way I've tried noise gates etc and that doesn't work either, sounds like it's coming from instead the preamp casing and is making an audiable noise threw the speakers.

[sgmypod]

well could be the mod or else valves on way out...

[jpfamps]

The problem with the pedals will most likely be due to a ground loop. These occur when there is more than one conduction path to ground, ie through the transformer used to power the pedal and the mains lead of your amp. To avoid this you will need to use either battery power, or use an (expensive) power supply which has transformer isolated outputs.

If the amp has been modified, then the ground in the amp could be suspect as well. Often modders ground the signal randomly to the chassis as this is easy to do, but can also result in a ground loop.

I am VERY wary of any amp that has been modified as I have seen some real horrors (although obviously I usually only get to see amps that have problems). Without knowing what the amp is or what has been done to I can't really expand much on this.

If the output valves aren't matched this can cause hum in the output stage. An easy way to test this is to remove the phase splitter valve (usually pre-amp valve closest to the power valves). Turn the amp on and anyhum you hear will be due to the power stage only.

Hope that this is helpful.

[greg]

it seems like you have a ground loop when using a pedal. it could be also poor filtering in a pedal's power supply, but it shouldn't affect when you use true bypass pedals. bare in mind some 'true bypass pedals' are not 'real' true bypass pedals.
if the amp cause it - those are usually old filter caps, unmatched valves in a power amp stage or unbalanced heaters voltage.
just do it step by step to eliminate the pedal, etc.
cheers,
g.