Amp Buzzing, Inexplicably

DESRTpunk · #1 08-21-2011, 01:00 AM

Well, I have this 15W Louis Amp (I live in Japan, hence the obscure brand.)

If it's on, and nothing is plugged in, no matter how much I mess with the settings, it will not buzz.
The second I plug something in, it starts buzzing. I could use the Cheapo Depot patch cable or some quality cable. But here's the part I don't understand, which makes me think it may be some grounding issue.

If my hand is on the strings, the buzzing goes away. Or if my hand is on the metal part of the cable, the buzz goes away. I figured it may be the bass, but with a different bass it still does the same thing, so I've isolated the problem to the amp.
Anyone have similar experiences or know a bit more about tron theory to help me out?

EDIT: This may be in the wrong section...

dhomer · #2 08-21-2011, 01:12 AM

You are right, it is a grounding issue.. Your hand breaks the ground loop. Normally the issue is with the bass. Its why some of the more expensive instruments have shielding in the control cavities.

One thing you might try for grins 'n giggles is if the power switch goes both ways, try it..

DESRTpunk · #3 08-21-2011, 01:15 AM

What do you mean the power switch?

dhomer · #4 08-21-2011, 01:23 AM

Some amps may have whats called a 2-way power switch. In effect what it does is reverses "polarity" in the power supply.. often times its used when you have shock issues w/other electrical devices like live microphones. If you amp has a simple on-off switch, then obviously you can't do this..

DESRTpunk · #5 08-21-2011, 01:27 AM

Ahh I see. No it's just a regular on/off switch. I'm thinking about opening it up, checking for any opens in the wires.

chadds · #6 08-21-2011, 06:26 AM

Is there a light dimmer barely on/off in your home?

billfitzmaurice · #7 08-21-2011, 06:34 AM

Quote:

Originally Posted by DESRTpunk

If it's on, and nothing is plugged in, no matter how much I mess with the settings, it will not buzz.
The second I plug something in, it starts buzzing.
If my hand is on the strings, the buzzing goes away. Or if my hand is on the metal part of the cable, the buzz goes away.

That's all normal. Keep your hands on the strings.

DESRTpunk · #8 08-21-2011, 07:32 PM

Quote:

Originally Posted by chadds

Is there a light dimmer barely on/off in your home?

No, I live in the barracks, no dimmers here boss.

I took the amp apart, shook everything out, then blew on it before wiggling all the wires to test if they were secure. I put it back together and the buzz is gone... I guess it just needed a shakedown and a reseat.
Thanks fellas.

billfitzmaurice · #9 08-21-2011, 08:24 PM

Quote:

Originally Posted by DESRTpunk

No, I live in the barracks, no dimmers here boss.

I took the amp apart, shook everything out, then blew on it before wiggling all the wires to test if they were secure. I put it back together and the buzz is gone... I guess it just needed a shakedown and a reseat.
Thanks fellas.

You may find it will return. With high impedance passive pickups environmental RFI and EMI noise is received by the pickups and cord. Most of it is shunted when you touch the conductive parts of the amp, cord or bass. Being environmental the RFI and EMI sources can come and go. The most common source of EMI is the power transformer in the amp itself, which radiates a magnetic field. But usually moving a few feet away is enough to suppress it.