Comet (DS-1) : crackling issue [SOLVED]

[eh la bas ma]

Hello,

I built a Comet kit and I have some crackling sounds mixed with the distortion.

https://aionfx.com/app/files/docs/comet_legacy_documentation.pdf

Here is an audio sample :
https://soundcloud.com/ehlabas-ma-chaussure/ds1cracklings

(Edit : noises are audible between 0:10' and 0:20', and from 1:04' to 1:15').

I am playing with active pickups. I chose to go with Mod 1 and Mod 2, according to the instructions, page 3. I didn't do the Big Muff mod.

This issue appears to be touch sensitive : when I am strumming the strings softly, there is no noises. There are crackling sounds if I am strumming a little harder .

Also, I noticed the cracklings go away when I turn the guitar volume almost all the way down (audio sample : from 0:30 to 0:50).

I tried this circuit with a RC4558 at first. I noticed the noises and change the IC for a TL72. It sounds a little better but the issue remains almost the same.

I never played on a DS1 before, or I don't remember it.

I wonder if it could be something to be expected from the circuit (with active pickups) ?



Any help would be welcome !

[antonis]

I have some crackling sounds mixed with the distortion.
Here is an audio sample :
https://soundcloud.com/ehlabas-ma-chaussure/ds1cracklings

No crackling sounds at all..
Just the "normal" sound of a quirky design..

[eh la bas ma]

I don't know if crackling is the right word : I would like to remove the noises that you can hear between 0:10' and 0:20', and from 1:04' to 1:15', if it is possible.

From 0:30 to 0:50, I turned the guitar's volume down and the noises are gone, isn't it a sign that there might be some kind of impedance trouble ?

This circuit sounds very good to my ears if I ignore the noises.  I built a few stompboxes with Aion's pcb, and they were all flawless, as far as I can tell.

Could the modifications 1 & 2 suggested in the instructions be the cause of this issue ? By "quirky design" do you mean that this kind of noises have been willingly added to the distortion, as a "good" thing ?

[antonis]

By "quirky design" do you mean that this kind of noises have been willingly added to the distortion, as a "good" thing ?

Can't tell about "willingly" but I shouldn't feed a Big Muff gain stage via a buffer..
(if it was on breadboard, I'd suggest you to place a 10k (or so) resistor between C2 & Q1 Base..)

[eh la bas ma]

Thanks, I'll try your suggestion and report back.
About the buffer, I am not sure I understand what you mean :

"The circuit remained unchanged until 1994, when it was modified to use the new PSA adapter instead of the old ACA. In the process, the op-amp was changed from a single to a dual—still the SIL (single-in-line) form factor, but the circuit was also revised to take advantage of this newly-available op amp, and a unity-gain buffer was placed in front of the adjustable gain stage. "

source : https://aionfx.com/project/comet-legacy/

Also this video, from Mr Wampler comparing SD1 and DS1 circuits, confirms that there should be a buffer just after the input (2:21).

https://www.youtube.com/watch?v=tpLms92E5qE

[eh la bas ma]

It sounds like it's fixed.

My values on C1 and C2 were wrong : 100n instead of 47n.

Thanks and sorry for my thoughtlessness...

Great sound !

[ThermionicScott]

Awesome, great to hear the rest of the story. 

[antonis]

About the buffer, I am not sure I understand what you mean

Never mind..

If it works by halving HPF (wrong) cap values, let it be..