Grounding Question

[Natman]

Hi all, I have a nice Blue Angel which sounds great. However, I suspect a grounding issue because when I touch the metal parts like chassis or chassis mounting screws, I get a reduction in hum. I first noticed when I touched the barrel of my patch cord (at the guitar's jack) and figured it must be the guitar, but none of the metal parts on the guitar do this so I think it's the amp. It even happens with the handle brackets! Any way of knowing what's up? I'd like to have this lower noise level at all times if possible!

Thanks guys

 

[Don]

Does touching the guitar's strings cause a reduction in hum? That would be normal to a degree. The guitar player is part of the grounding circuit.

I would start by testing the outlet with an outlet tester and I would also chack for potential on the amp's chassis and the guitar's strings with a voltage sensor. Most will tell you is more than 70 volts is present.

 

[94Tremoverb]

Like Don said, it's normal for touching a grounded part of the amp or guitar to reduce hum.

If *other* metal parts of the guitar don't do the same thing (especially things like the screws/nut on the selector switch), the problem is with the guitar not the amp - all the metal parts should be grounded. The bridge/tailpiece/strings should normally be on a passive-pickup guitar, although not with EMGs or other active pickups. It's also sometimes done to connect the bridge ground via a safety cap - so there isn't a direct connection - but then touching the strings should still reduce the hum.

A big change in hum when you do this might indicate your AC supply is badly grounded though.

(If it matters, the handle brackets contact the shielding in the top of the amp cabinet via their mounting T-nuts, which is why they work like that too! )