Grounding question

[surfsup]

My amp is starting to do something it didn't do before. If I don't touch it, or the strings of my guitar, etc, it sometimes hisses very loudly with a hum.

Didn't do this before.

I suspect some sort of grounding issue. I tightened all the star grounds, etc. and it went away, then later today I fired it back up and its doing it again.

Nothing changed, could my input switchjack be malfunctioning?

[Firestorm]

How does it sound with nothing plugged in?

[surfsup]

No problems with just the speaker hooked up. Sorry forgot to mention that. A little bit of hiss cranked but that's to be expected.

[Firestorm]

Try different cable, different guitar. Then clean up the input jack itself: maybe dirty, maybe slightly sprung.

[surfsup]

I tried a different guitar. Same problem.

I'll try a different cable as well.

I can't see it being dirty. The amp and jack are only a month old from new. Only left the house once. But ya never know...thanks.

[martin manning]

Did you try swapping tubes?

[backpack]

did you look for loose pots and cold solders that may have came loose from transport.

[surfsup]

I didn't swap tubes b/c I felt tubes had nothing to do with it as it is not happening w.o a guitar.

I didn't check pots either... if it doesn't have this problem w.o a guitar, why would it be a pot, etc?

Without guitar plugged in, the amp is totally fine.

[martin manning]

I didn't swap tubes b/c I felt tubes had nothing to do with it as it is not happening w.o a guitar.

That says your input jack ground and switching contact are good. When you plug a guitar in you are un-grounding the grid and applying signal, even if its noise and rf. Swapping the tube takes less than a minute and rules that possibility out.

[backpack]

I didn't swap tubes b/c I felt tubes had nothing to do with it as it is not happening w.o a guitar.

I didn't check pots either... if it doesn't have this problem w.o a guitar, why would it be a pot, etc?

Without guitar plugged in, the amp is totally fine.

If the pots are a grounding source and the have a poor conection...
Also I use my amps with guitars, but I am intrested in how you use yours.
If you suspect grounding and not dc bleeding into the ac just look at all
your grounds with a meter.

[Structo]

Also as you probably aware, with a guitar plugged in and without you touching it, the amp will hum more loudly until you touch the strings or other parts that are connected to ground.
Your body grounds the guitar on your end.

This is especially worse with single coil guitars.

But if it is a new thing than the first thing I always do is start trying different tubes.

I had a NOS GE 12AX7 that I paid big bucks for that after a while became so noisy I couldn't use it anymore, really torqued me off.

[surfsup]

Okay, yea it all goes away touching the strings. The humbucker LP is worse than my SC. I will try to swap tubes first and check the pots.

This is a new thing. It didn't do it nearly this bad before Thursday night...

[martin manning]

How good is the earth ground to the chassis and at the wall? Poor grounds there can cause the hum that stops when you touch the strings.

[surfsup]

How good is the earth ground to the chassis and at the wall?

To the chassis very good. To the wall? I am using an old power strip.

I'll pull that outta the equation.

[surfsup]

Well its either the power strip or the room/house electrical. I moved it all into the livingroom and plugged the amp direct into the wall. Problem solved. Shitty house...