How to reduce an audio system noise in a way which is similar to a human touching one of the system's components?

Question

I have a somewhat weird question (hopefully not too weird).

I work with an audio system. It includes a wave generator, a (33500B series Keysight) wave generator, an amplifier (2003 op-amp based circuit, will be replaced with LM1875 circuit in the future) and a speaker (H1283 Seas Prestige). I use BNC cables between the system components.

Here is my problem, I have background noises (even when the generator is on but not outputting any sounds).

I noticed, that the best thing to reduce this noise is me touching one of the system components (not speaker but wave generator, audio amplifier or the metal ends of the cables).

I am not sure why is it so. Is it because I am a huge capacitor?

Anyway, here is my question: (Since I can not hold the boxes while applying the experiments...):

What is the simplest action I can apply in order to create a similar effect to me touching the system components?

I already tried:

1. Attaching a metal mesh (to create a "Faraday cage" effect).
2. Attaching parts of the metal mesh to components of the audio box.
3. Connecting the boxes to an external ground.
4. Connecting the grounds of all the boxes.

All these things helps a little. But nothing has the effect of me touching the boxes.

Any ideas?

Answer 1

It "sounds" like a ground loop or an impedance mismatch, but if everything is properly grounded, then a ground loop seems unlikely, but then again, if everything were perfectly grounded, then you touching anything should have no effect. In either case, a ground loop isolator should help significantly.

A ground loop isolator prevents interference in a ground loop circuit. A ground loop circuit is one in which two or more circuits are connected to the same ground wire. Ideally, all circuits in a ground loop circuit have the same voltage potential. However, if the ground wire has significant resistance and current, the voltage of the second circuit will be slightly lower than the first, causing a voltage difference that makes the ground wire no longer have a ground potential. This is known as interference and can be hazardous, inefficient, and a nuisance in many electrical systems.

Although they are not very expensive, be aware that there are different ground loop isolators for audio signals and video signals, so be selective when shopping.

Answer 2

In the car audio world, we ground the RCAs to the chassis of the head unit. Ive never worked with wave generators, but it may apply.

Answer 3

Try loading it (shunting it) with, say 10 megohms or greater. This may help by loading open outputs, providing a discharge path for built up charge, etc. Worth a try.