Noisy input

[GroovyMan]

Hi all,

I've pretty much completed my second scratch build - a Ross Compressor. I'm very pleased with it and I think it's working as it should.

One observation I have has is that when switched on I get a bit (not huge amounts) of pops and crackles. I'm guessing this is noise on the input which is then being evened out by the circuit. I gets worse when I run my fingers over the switch terminals and input jack.

I remade the connections from the input jack, though the switch to the board but it doesn't seem to help.

Does anyone use screened cables for this type of application? Do you think it would help?

Thanks,
Ben

[Processaurus]

Shielding the input wire on hi gain effects  is a good place to start with noise issues, but pops and crackles aren't normal for your Ross.  Maybe open it up and poke stuff with a plastic pen (or anything not metal) to see if there's something that is the source of the crackle.  Also beep the things on the chassis that pop when you touch them to circuit ground to make sure all the external metal stuff is grounded.  Maybe try adjusting the trimpot again, or another 3080. Just some ideas, where I'd start if I was cracklin'.

[GroovyMan]

Thanks for the tips, I'll try those out.

I haven't adjusted the trim pot yet as I'm still trying to understand what it does. One description I've read is that it can filter out "control voltage noises". Does this sound like what it could be?

Ben

[Processaurus]

Thanks for the tips, I'll try those out.

I haven't adjusted the trim pot yet as I'm still trying to understand what it does. One description I've read is that it can filter out "control voltage noises". Does this sound like what it could be?

Ben

Not sure what it does electronically, but you just tweak it until you don't hear distortion.  It's not a touchy adjustment, a wide range works, I tried to find where the positions on each side where it distorts were, and then put it right in the middle between the two.

[GroovyMan]

Well I fiddled with the trimmer last night.. and it did have an effect on the noises. I turned the sustain control up full and then altered the trim.

It seemed to have no effect on from about half way upwards, but as I turned it down the pops and crackles started to get less and less, however the tone gets more and more muddy. So I set at a point where the noise was bearable and tone was clear.

Thanks again for your help.
Ben

[Processaurus]

I'd try a new 3080.  That trimmer isn't supposed to be a muddy sound vs rice krispies.  It just makes it distort less when it's set in the right ballpark.