Shielding Question

[BigBadBen67]

Ok, bass porn first, then I'll ask my question:

So I built this with a Warmoth body and neck and a set of CS62 pickups. I absolutely love it. The tone and feel are magical.

But I'm having a hum problem. There's a noticeable hum if I'm not touching the strings. I pulled it apart and covered both the pickup cavity and the control cavity with that sticky backed foil they sell for this. That helped considerably but there's still more hum than my other bases.

Is there something better I should be using for shielding? I've heard of spray-on paints and that sort of thing. Does that tend to be better than the stick-on shielding?

Thanks,

Ben

 

[dwizum]

"Better" is a bit of a challenge. The different products are definitely "different" but if you ask about better you start getting into personal preference (in terms of application process) and a lot of theory that doesn't always have practical support. I can tell you that I've never met a guitar or bass that specifically needed shielding and had foil tape not work. But of course the painted-on products are successful in many instruments, too. Basically, I don't think it's your choice of product that's the issue.

Can you show us your cavities? Is the foil in the pickup cavity connected to anything? If so, how? How is the foil in the control cavity grounded? Is the wiring channel between the two cavities shielded as well?

You've mentioned that it has more hum than your other basses. That usually rules out environmental factors, but just to be sure - can you try the bass with another cable, and another amp? How about in a different room?

 

[BigBadBen67]

Thanks. I’ll see if I can get pics. The foil in the control cavity is grounded to the pots and the jack by contact. The foil in the pickup cavity isn’t grounded. It’s definitely just this bass. I have several others and none of them have any hum.

 

[Danny C]

I run a wire between both cavity’s and secure each end, check continuity and that seems to help.

 

[dwizum]

The foil in the pickup cavity isn’t grounded

In that case it's dong (almost) nothing - it needs a path to ground. You can run a wire between the cavities as @Danny C suggested or switch the pickup wiring to shielded cable and connect the cable shield to the foil tape on both ends.

 

[BigBadBen67]

Thanks. I'll try grounding the pickup cavity foil and see if that helps. More in a bit.

 

[Tommy Sparks]

Simply put. All shielding, pots shells bridge and jack shell must be connected.
Also l like the porn
I have the same desk.

 

[BigBadBen67]

Simply put. All shielding, pots shells bridge and jack shell must be connected.
Also l like the porn
I have the same desk.

Yeah, thanks. I didn't realize that with the shielding needing to be grounded. I'll make double certain it's all grounded.

Once that's done this bass will be just about perfect. I don't want it to be something I dread taking to a studio for fear of the hairy eyeball from some engineer.

 

[BasEd]

I’ve just shielded a passive PJ with copper sheet. Pickup and control cavities. All connected with wires to a central point and then to the earth, including the bridge wire. Cured 95% of the hum. Apparently shielding is only needed for passive components. I replaced the pickups with active EMG PJAX and now there is zero hum.

 

[BigBadBen67]

I’ve just shielded a passive PJ with copper sheet. Pickup and control cavities. All connected with wires to a central point and then to the earth, including the bridge wire. Cured 95% of the hum. Apparently shielding is only needed for passive components. I replaced the pickups with active EMG PJAX and now there is zero hum.

I actually tried that. Didn't like it. To my ear it sounded too sterile. I like that warmth the vintage style pickups have.

 

[BasEd]

EMGs take a bit of getting used to as they have a large dynamic range so lots of top end that you don’t get with passive pickups that need thousands more winds to get the required output. You can use the tone control to take off some top end. Passive pickups sound a bit dull once you get used to EMGs.

 

[BasEd]

At a gig the EMGs really shine.

 

[1bassplayinfool]

Solder your ground(s) to the foil and see if that helps... good luck.

 

[Killing Floor]

Did you run a ground wire under the bridge?

Also, you seem nice. You don’t have to show TB your cavities when they ask. This is a safe place.

 

[Kukulkan61]

Wow! That is gorgeous!

 

[CarpeBasso]

Yes, the ground wire to the bridge must make good contact. Every ground connected in some way to the other grounds & copper foil.

 

[EatS1stBassist]

Ok, bass porn first, then I'll ask my question:


View attachment 4134225

So I built this with a Warmoth body and neck and a set of CS62 pickups. I absolutely love it. The tone and feel are magical.

But I'm having a hum problem. There's a noticeable hum if I'm not touching the strings. I pulled it apart and covered both the pickup cavity and the control cavity with that sticky backed foil they sell for this. That helped considerably but there's still more hum than my other bases.

Is there something better I should be using for shielding? I've heard of spray-on paints and that sort of thing. Does that tend to be better than the stick-on shielding?

Thanks,

Ben

Check the bridge ground.

 

[Roxbororob]

Also if the foil you used doesn't have conductive adhesive the pieces should be grounded to each other (a bit more soldering).

 

[alembicguy]

Did you run a ground wire under the bridge?

Also, you seem nice. You don’t have to show TB your cavities when they ask. This is a safe place.

This

 

[BigBadBen67]

Did you run a ground wire under the bridge?

Also, you seem nice. You don’t have to show TB your cavities when they ask. This is a safe place.

I’m not shy. Just lazy.