AC and Noise

[C Moore]

Just wondering how much noise potential there is from One, AC, 3.5 volt heater wire.?
I am using an old PA chassis that has a switch, on the front faceplate, that is empty. The amp has lights, and I was thinking of using this switch to turn the lights On and Off.
At some point, I would need to run a single, 3.5 volt wire across a ground wire and a signal wire that is used for the Tremolo circuit. So, I am wondering if a single 3.5 volt wire can cause a lot of "noise" issues.?
Or perhaps, just in theory, how much noise can a single, AC, 3.5 volt wire cause if it needs to cross over other wires in an amp circuit.?
Thank You

[Structo]

Well you would want to keep it clear of any preamp grid wires that's for sure.

Sometimes you can route a wire like that around the outside edge of the chassis to avoid preamp wires.

If you do have to cross other wires elevate it as high as you can and cross at 90 degree angle.

[C Moore]

Thanks Tom -
All the "common sense" stuff (wish it was more common in me).......
It just seemed like it was going to be bad, so I drilled a hole, terminated the wires different than originally planned, and avoided that situation.
Guess I was just kind of wondering, when applied to what we do with guitar amps......all else being equal, does 120VAC cause more noise than 3.25VAC.?
Thanks

[Structo]

That is a good question, in my mind I think yes, a 120vac line is going to have a larger pattern of EMI than a 6.3vac.

[Jana]

". . . in my mind I think yes, a 120vac line is going to have a larger pattern of EMI than a 6.3vac."

Not necessarily. It also depends on the amount of current that is being drawn through the wires.

[martin manning]

The concern is that the time varying magnetic field surrounding AC power supply wires will induce currents in nearby signal wires and produce noise in the signal path, and the strength of the magnetic field produced is proportional to the current, not the voltage. A single wire is more problematic than a pair... heater wires are twisted together because they carry high current, and it is hoped that the field from one wire can be made to cancel the field generated by the other because the current is flowing in opposite directions, and the twist keeps them close together and parallel.