Hum topic again

[gahult]

Rocket is done but it brings up a question in regards to hum on builds some with more some with less.

The amp is dead quite very little noticeable hum or hiss even with vol. maxed.

When I plug in the guitar the hum is at an unacceptable level.

Any preamp (V1-V3) pulled and no hum guitar plugged in or not.

Am open to any thoughts on this. I know it's been covered many times but searches bring up to many topics to wade thru.

Gary

[martin manning]

If it's quiet with nothing plugged in, it's very unlikely that the amp is the source of the hum, but plug a cable in and measure the resistance from the tip to ground. You should see the 1Meg input grid resistor. Single-coil pickups will always hum in the presence of stray 60 Hz EMF, of course. Poor grounding in the guitar wiring can produce hum, and I suppose the cable could be at fault too.

[Phil_S]

Do you have florescent lights and/or are you using single coil pickups?

Do you have a cell phone? Is it in your pocket near the guitar pickups?

[gahult]

No cell phone, no florescent lights.

Humbuckers on LP Electra, single coils on two different SX guitars.

See 1M on cable tip.

Gary

[davidjon_99]

No cell phone, no florescent lights.

Humbuckers on LP Electra, single coils on two different SX guitars.

See 1M on cable tip.

Gary

You've probably done this, but have you tried different instrument cables?

[M Fowler]

Gary I had to start isolating the input jacks or use Cliff jacks on my Trainwreck builds to get rid of that hum.

[Stevem]

To test out a givin Amps hum and hiss level I have a 1/4" Jack that I have shorted out and into the input Jack it goes then open up the amp full on, any added noise is the amp only, you can do the same thing with plugging in the axe and turning its volume(s) down and this will show up if a cord is poorly sheilded and or what the short lengh of wire from its input Jack to the volume pot is adding to the noise level.

[Reeltarded]

^^^^^ If it makes it there it makes it anywhere.

[guitarmike2107]

possibly just had a similar problem, with the guitar plugged in and turned all the way down is the hum gone? if it is the its coming in through the guitar so start turning off all lights and wall sockets possibly even at the fuse board to see if you can make it better.

my problem was a pedal power supply that went bad and was plugged into the same socket, I had no hum amp worked fine, I added an effects loop then all of a sudden hum, so ended up removing the effects loop, then rewiring the whole pre-amp , pulled half my hair out, then I tried the guitar source as above, gutted I did not try that sooner

[Stevem]

I have has issues with two prong wall wart type power supply's in regards to hum and I have had to plug them into one of my old ground lift adapters that have both blades that same small size so you can spin it around!
These days with the new ground lifts I have to notch and grind back the fatter blade so it can be plugged in the other way.
If you have a lot of external things plugged in then it's best to plug them all into a power strip that has a ground lift on its end and then if you still have a hum issue that will not fall inline put on sperate adapters and pivot those around to releave the issue which is in situations like this a ground loop.