Noise ...

[poiureza]

Yesterday I changed my workspace and breadboard setup for a better ... or so I thought

I'm getting an annoying background noise now. I'll be going through all the changes to trace the culprit but maybe this is a known issue :

I get a low frequency beat (<5Hz) that sounds like a purring kitten.
Happens only if the breadboard circuit is powered up (9V battery) AND the guitar input is connected. Dead silent if guitar cable is removed.
So I suspect the guitar cable is making for an antenna ???
Yet I don't pick up radio stations, only that purring sound.
Is that what's meant by heterodyning maybe (just throwing words around here) ??

[FenderLover]

can you kill the noise if you short the other end of the cable?

As long as the circuit is quiet by itself, your circuit is probably OK. Like turning up an amp with nothing plugged in. Compare that to the noise of single coils or hummbuckers plugged in. I've seen folks blame the amp for the noise because that's where it (seems) to be coming from.

[poiureza]

Do you mean grounding the jack that goes into the guitar ?
I'll have to try that, have to build a new circuit first as I discarded the previous one.

The circuit by itself was dead quiet, the amp made some noise when turned fully up but no more than it does with nothing plugged in. As soon as I plug a cable to the circuit input it starts purring, even with guitar not being connected.

I thought it had to do with the location of my guitar->circuit cable on my bench (I attached it on the bench) but it did the same with a free floating spare cable.
Weird.

[petey twofinger]

hello from chicago, i am no expert , from my little understanding ...

heterdyning would be a constant hi pitched compu noise , like a ticking oscilation . i think its when you are running two circuits that have clocks in em , off the same power supply . i made some battery amps with sealed lead acid cells in them . i also put 9 volt regulators in there so we could power a few pedals off the amps at the forest or outdoors . with the digital modeling multi effects we had this high sounding annoying " ging ging ging ging" goin on . i unpleged the pedals power , then ran the powers to oposite rigs . so my kids rig was powering my ole ladys and vice versa . prolum solved ! lol . i am guessing with ferrite beads and capacitors i may have been able to tame it a bit or eliminate this , but ....

if i am understanding you properly , you have a circuit that the audio is running thru on a breadboard , if this is the case then yes , there is an antennae going on , more likely the actual circuit on the breadboard is picking up interference . i would think perhaps a shoebox , covered in tinfoil , with a ground wire , might just do the trick . sure its a bit hackish but , i embrace this sort of style for temporary adjustments . it sure beats noise !

i am prolly totally off here though so ... once again not an expert . i just try to offer suggestions , randomly .

[cousinpaul]

Could it be proximity to another device (computer, TV, cell phone, etc)?

[poiureza]

Originally Posted by cousinpaul

Could it be proximity to another device (computer, TV, cell phone, etc)?

That's a possibility for sure.
I still didn't get to investigate though as I'm in the middle of a f******* plumbing work (water pipe leaking right between 2 floors)
Gotta love these old WWII houses

[poiureza]

Repaired the water pipe and breadboarded a couple new circuits and now the noise is gone.
So I guess the water pipe was the culprit