Vanishing point noise

[Bernardduur]

OK, another one!

I have build the vanishing point succesfully. And it sounds really nice...... but I have some clock noise. I checked the advise on the vanishing point website and searched this site...... the only succes I had was by isolating the psu.....

Any thoughts? The distance between the audio and the clock is around 2 or 3 cm.....

[The Tone God]

Isolating is not just a physical distance but a electric property meaning isolating power supplies, using ground planes, removing ground loops, etc. Are your grounds connected together at one point ?

Andrew

[Bernardduur]

They were; then I had clock noise. Now I have two psu's = no noise. But it is kinda "frustrating" having two psu's

Here are two pics:

Pic 1: overview
Pic 2: closer

Upside is sequencer, downside is super tone control and middle is charge pump

[The Tone God]

Ok so two PSU does not create noise so the wire and clock noise is not leaking from there but from the power supplies. Have you isolated the supplies with 100ohm-1K resistors and a cap to ground ? Are you using a charge pump like a 1044 or 7660 ?

Andrew

[Bernardduur]

Nope, I did not isolate them...... ; how do you isolate a PSU??

I use a charge pump for the super tone control (for + and - 9V)

[The Tone God]

Nope, I did not isolate them...... ; how do you isolate a PSU??

Put a 100ohm-1K resistor in series with power supply input (i.e. between the battery and the circuit's input) of each section meaning the digital portion, Vanishing Point, and the audio section. Right after the resistor connect a cap, like say a 100uF, going to ground.

Also it might be a good idea to put decoupling caps on each of the logic IC. This is a small cap like say 0.1uF (ceramic is good) on the power input of each logic IC going to ground. Put these caps as close to the IC as physically posisble.

I use a charge pump for the super tone control (for + and - 9V)

Hmm...I don't know how much the logic stuff would like playing with a charge pump. I haven't tried it but its something to think about if the above doesn't help. Why are you using a charge pump ? Is this an opamp based circuit ?

Andrew

[Bernardduur]

Yep, it is an opamp based circuit of a high pass / low pass / band pass circuit.... I use two LDR's to control the frequency of the filter and it works quite good.....

I will try the isolation!

[The Tone God]

Are you running a bipolar supply for any particular reason ? Depending on the circuit you could run it of a single supply. This would eliminate the need for the charge pump. Just a thought if the charge pump turns out to the be the issue. You can try out the circuit without the charge pump using another battery to see.

Good luck.

Andrew

[Bernardduur]

The isolation worked great; no more noise.

Ehm, the charge pump; I need to run the circuit on bipolar; maybe it can be run on a single PSU, but I can't figure that out yet I guess.... I tried some, but still came back after the stability of the bi-polar......

[The Tone God]

The isolation worked great; no more noise.

Excellent! Glad you got it working.

Ehm, the charge pump; I need to run the circuit on bipolar; maybe it can be run on a single PSU, but I can't figure that out yet I guess.... I tried some, but still came back after the stability of the bi-polar......

Check out this article as it might help out:

http://www.geocities.com/thetonegod/opamp/opamp.html

If you need the headroom of the full 9v swing or you just like it better then you can stick with the bi-polar supply. I just thought it would make things simpler

Andrew

[Bernardduur]

Ah, thanks Andrew. Great article


I already tried it like that, but the headroom is really what I need...... without the bi-polar the bass get's distorted very quickly

[The Tone God]

If it works for you then cool.

I hope you enjoy it and when your done The Tone God demands pictures!!!

Andrew

[Bernardduur]

OK, I got noise again when I boxed it up..... Any thoughts?

I got (I guess) clock noise that responds to the filter. Even in bypass mode I have noise (no filter).

What I've done:
- Kept both circuits from each other
- PSU isolation
- Kept wires from each other

Edit: I hear two ticks per sequence. Remove bypass tick by isolating the in and output wires.

Oh, one last thing........ whith the filter set too high I get a "pop"

[The Tone God]

Have you changed the circuit at all before you boxed it up ? Was it noisey when before you boxed it ? I'm leaning towards noise leaking in through messy signal routing.

Andrew

[Bernardduur]

Nope. Didn't change at all. It was quiet before I boxed it up, now it is here.....

I've fixed it by adding a barrier between the filter and the the knobs / wires / etc. It is made from aluminium foil covered in ductape with a wire going to ground. Works great!

[The Tone God]

Ah ground plane! I think I mentioned something about that in the v2.1 article.

Good job. I hope you enjoy it.

Andrew

[Bernardduur]

Yes, I read it there! Covers now everything and the unit is now silent.


Pics:




Some info:
- Low pass / band pass / high pass and notch filter
- switch between step and autowah filter
- both Q as speed can be controlled by a expression pedal.

[The Tone God]

Right on. Nice pics. The Tone God is pleased. Impressive collection of features as well. I even like the colour which is rare thing with me.

Be proud. You deserve it.

Andrew