Low hum in LB6

[Ex202]

I've got a low hum in my LB6. It the kind of thing that decreases when I touch the output jack. Is that fixable or does it indicate an internal ground problem in the LB6?

[Caleb_Elling]

Hey Ex202,
Are you running the LB6 with a preamp on the guitar or is it passive? Is the soldering connection shielded?

Usually, if the hum goes away when you touch the jack, it's a shielding issue.

[Ex202]

Running it on one side of a MixPro. The other side is an electret mic. The connection is shielded, but I need to recheck the joints. It's an old output jack that's been used several times on various projects. I assume it's not necessary to do any special shielding … simply connect the ground to the output jack. Right? Do you ever see LB6s with such problems? Just trying to figure the likelihood of it being the pickup.

[Caleb_Elling]

The only time I've seen anything like this with an LB6 has been when the pickup was damaged by the installer and the Micarta top was separating from the brass.

The ground from the pickup does need to connect to the ground on the jack, but the jack also needs to be shielded. Does your jack have a barrel shield? Or something else?

You might want to try another cable too, just for comparison. Even a mono cable into the Mixpro would work for troubleshooting.

[Ex202]

Thank you so much, Caleb. Used mono cable to troubleshoot … turned out that although the old cable looked good – Neutrix connectors, good solder joints – there's was an ugly ground problem somewhere in the cable itself. So, into the trash it goes. Who would have thought … well, you did!