Hum disappears on touching both strings and cable? What is the issue?

Question

I have got a Taylor 312ce 12-fret. I actually rarely plugged it in at home, but I did now due to a new pedalboard. Thereby, I discovered a hum issue.

The simplest setup on which it occurs is:

Guitar --> acoustic amp

In this setup, the hum disappears if I touch the cable and the guitar strings. Considering that this is a grounding issue, the internet states that it should be sufficient to touch the strings. This however does not work alone and even does not make any sense to me, since I am not grounded either.

Another setup:

Guitar --> effects --> boss looper --> acoustic amp

In this setup I can even make the hum disappear by touching the metal body of the looper.

An amplified recording of the hum (ignore the other noise, it is introduced by an external preamp which is another issue) can be found here. The hum in this recording disappears while touching strings and cable. I do that a few times.

Since the hum only disappears if I touch the strings and ground myself somewhere I do not consider this question as a duplicate. I would rather like to formulate the question as: Is it normal for my guitar that touching the strings alone does not stop the humming?

Answer 1

With an acoustic/electric guitar, you are usually dealing with a mostly standard acoustic bridge, where there is a piezo pickup mounted underneath the saddle where the strings run across.

In an electric guitar, the strings are physically connected to a metal bridge that IS grounded into the circuitry of the guitar. In an acoustic/electric guitar, that does not have to be the case (strings are not necessarily grounded or attached to the circuit).

It's possible that there may be something not-quite-right in the electronics of the acoustic guitar, or this might have to do with more subtle things in your electronic circuit: ground/ac power.

Ground loops are a somewhat common cause of noise in a guitar circuit as the circuit grows in complexity. They can be tricky to troubleshoot, but since the hum happens even when you just have the acoustic going right in to the amp, it could also have to do with a poor or noisy ground in the circuit that the amp and stuff is connected to.

One simple way to test if the issue is caused by a poor/noisy ground would be to get one of those three pin to two pin Polarized Grounding Plug adapters. Plug your amp in to that, then in to the wall, and leave the ground disconnected. Turn the amp/guitar on and see if the noise is gone.

I've had polarized grounding adapters fix noise issues in some situations/circuits before, so that may be worth a shot.

Power conditioners are another thing that can help reduce the overall noise floor in a setup. If the polarized grounding adapters correct the noise, a decent power conditioner may also help to correct the issues, while maintaining a ground connection and surge protection.

Hopefully this answer is not too late to help!