My debugger needs debugging! (very noisy)

[Royalston]

Ive made an audio probe to debug my orange squeezer ( no one wants to help me on the forum...poor me javascript:void(0); )
But its really really noisy. It uses a cap and half a guitarcable (like the in the FAQ)
I can hear my signal when I touch the tip of the cap at the audio in, but only just, due to this noise - why is this?

Thanks
Royalston

[Royalston]

please javascript:void(0);

[D Wagner]

Royalston,

Do you have a circuit ground connection? 

You have your input signal at the point where you are touching the circuit, but you also need to connect to the circuit ground.

I hope this helps.

Derek

As an alternative, you may want to consider something like this http://www.talkingelectronics.com/Projects/MiniBenchAmp/MiniBenchAmp.html  I "cloned" one from the information on the page, but it is cheap enough to buy one.  It is self contained (no need for an amplifier) and it works great!

[Royalston]

hey hey
Derek!

Thank you for answering me! javascript:void(0);

Ive posted 3 different messages (pleas for help, over the last week, and received 0 replies) - so Thank you.

ahem. no back to the matter:
Yes, I have the an alligator clip attached to the ground of the circuit. There is a hum in the amp when its on and the debugger is plugged in, but thats not too loud. But when I attach the grounding clip, the hum is REALLY loud... does this say something about my circuit?

Any ideas?

Thanks again javascript:void(0);

Dylan

[tiges_ tendres]

what do you have feeding the input of the circuit?

[Royalston]

Im not sure...

I'll tell you what I know I have:

The pedal, with a drum machine plugged into the input.

Then the audio probe:
Guitar cable, one end plugged to amp, other end - shield wire connected to circuit ground, other end attched to Capacitor and I probe the circuit with this...

When I attach the shield to ground, the noise increases like crazy....

[tiges_ tendres]

hmm, maybe try something else in the input.  I use a walkman, with a self help tape in it, just to keep me from going crazy if I cant find the problem!  "relax, breathe, your troubles are drifting away"

I'm wondering whether the impedence of the drum machine might be causing you a problem, is the drum machine usually noisy?

Another problem could be that the circuit might not be correctly grounded in the first place, making adding another source into it, even noisier.

[Royalston]

calm blue ocean...calm blue ocean

Thanks I'll try something else

I think the effect is properly grounded. Any way to verify this...?

[tiges_ tendres]

calm blue ocean...calm blue ocean

Thanks I'll try something else

I think the effect is properly grounded. Any way to verify this...?

Easiest way is with some kind of diagram.  That's still no guarantee, but at least we'd be able to take a better guess.

The ground from the board goes to where? see if you can draw us up a digram for that.

[Royalston]

hmm

where does the ground from the board go?

no idea!
Where should it go? The board is just connected to the battery and the cables....

[vanhansen]

Try using it in reverse.  Plug the drum machine in to the probe, or hook the probe to the drum machine, and then connect the circuit output to the amp.  That's how I use mine.

On the end of the probe with the capacitor, do you have a long lead wire with a clip on it from the ground lug of the jack?  That needs to connect to the amp chasis.  That's how I've been instructed to use it.

My probe consists of a 1/4" mono jack with a long lead and a clip off the sleeve lug and the capactitor on the tip lug.  Like this one:



My guitar plugs in to it as the source, circuit output to the amp.

Ground from the board goes to ground.  All your ground connections need to tie together.  This includes the ground lugs of the jacks, volume pot and the circuit board itself.  What I usually do is connect the ground lugs of the jacks together, run a ground wire from the circuit ground to one of the jacks ground lugs, and then the volume pot ground to the other jack ground lug.

[Royalston]

vanhansen
I like your idea of using it in reverse...but if I dont have something plugged into the IN jack, then I dont get sound. (Im using a DPDT switch.)

Both my jacks, and the board go to ground as in the schematic...but I still get that hideous buzz. I even got a guitar and tried that, but the result was the same....

The alligator clip should connect to the amp chassis - but where? I think this may be my problem....

[gaussmarkov]

first time i read the title of this thread i thought it was "my daughter needs debugging!  (very noisy)" 

can you make a freudian slip reading something?  

[vanhansen]

vanhansen
I like your idea of using it in reverse...but if I dont have something plugged into the IN jack, then I dont get sound. (Im using a DPDT switch.)

Both my jacks, and the board go to ground as in the schematic...but I still get that hideous buzz. I even got a guitar and tried that, but the result was the same....

The alligator clip should connect to the amp chassis - but where? I think this may be my problem....

Your guitar/CD player/or whatever you use as a sound source feeds the input.  You are connecting one of those things to the probe.  Naturally nothing is going to the input jack because the probe is taking it's place.  If you went the other way with the guitar/CD player/or whatever you use as a sound source feeding the actual input jack, then the probe would serve as the output and would connect to the amp input. 

Connect the alligator clip anywhere there is metal.  Take one of the knobs off if you have too and clip it on to the pot shaft.  On the back of my Crate GX-15, there's little air vents that are perfect for clipping to.

That's a pretty good slip there, gaussmarkov.