Circulator does a regular "pop" (LM13700 sub by NE5517)

[mrguep]

Hi there,

I recently build a circulator kit ordered from Musikding, and as usual (or maybe I'm unlucky) there were some missing components, in this case, the LM13700 where not here.
So, tired of waiting for thoose now rare IC's, I've checked for a LM13700 substitute and NE5517 seems to be a good candidate (AionFx tells that it's the same parts, just different manufacturers -> https://aionfx.com/component/ne5517n/ )

Also, I did the @Chuck D. Bones mods below (by the way, he did an awesome job, big up!):
8. Added a 3.3Meg resistor (R109) from pin 3 of the RATE pot to IC1 pin 3 (Vref). Along with item 9, ensures that the LFO will always start and never stall.
9. Added a 22K resistor (R107) from IC3 pin 8 to IC3 pin 6. Along with item 8, ensures that the LFO will always start and never stall. 8 & 9 must be done together, I consider them mandatory.
11. Increased R27 to 33K. In the original design, the Circulator will break into oscillation when RES is dimed. I have no use for a pedal that screams at me. With this mod, RES has plenty of range and stops just short of oscillation. Totally optional.
12. Added a Throb LED (R108 & LED2). I think any pedal that has an LFO should also have a Throb or heartbeat LED. I prefer that LED to run all the time, not just when the pedal is engaged. R108 is soldered to LED2 and has clear shrink sleeve over it. Any color LED will work. Do not make R108 less than 10K; if your LED isn't bright enough, get a different LED. Totally optional, but if you do this you need to do items 8 & 9 to ensure that the Throb LED doesn't stop the LFO.

The pedal fires up, throb LED throbes, all pots works, I can clearly hear the effect but there are 2 issues:
1- A "pop" is audible in each "phase cycle". It matched the rate control, it's getting louder when rate goes faster, i feel it's changing with swap control but i couldn't describe it clearly. Here is a record of that sound with rate changing. Resonance control doesn't affect this "pop".

https://soundcloud.com/little-massive-hifi%2Fcirculator-pop-cycle

2- Even I did the @Chuck D. Bones mods to prevent LFO to stall or fail starting, when I turn the rate down, LFO stops.

Could thoose 2 issues could be linked to NE5517/LM13700 swap?

Has anyone ever encountered thoose issues?

Help would be really appreciate

Thank you all!

 

[eh là bas ma]

I had a similar issue once, trying to add a Rate led on a Dandy Horse (EHX Echo Flanger).

If i remember correctly a capacitor fixed it somehow but i can't remember precisely, and i sold this build.

Did you try to disconnect the Rate led and see if the pop is still there ?

 

[mrguep]

Hey @eh là bas ma !

Un big de Nantes sud! Je vais poursuivre en anglais pour le bien commun

Yes, I first tried to disconnect the LED (only ground side, it was easier) but nothing changed. The "pop" and LFO stalling are still in here... So I put it back.
What do you think of the LM13700/NE5517 swap I did? Could the issues I get comes from this?

Merci!

 

[eh là bas ma]

Nantes ? Ici Rennes.

I found my old post, see reply #3 : https://www.diystompboxes.com/smfforum/index.php?topic=126431.msg1208896#msg1208896

In my case it was weird. Adding an extra Rate led introduced some ticking noise much like yours. The circuit remained noisy even after disconnecting the led. Looks like i managed to get it quieter by trying different ground points for the led. I know i got it fixed but i really cant remember precisely how... Maybe it was a different led color, i think i used a 3mm orange one in the end.

About the IC substitution, looking at both datasheets they look the same, i guess we can trust Aion Fx. It's the perfect sub according to them : "will perform the same in any application". If there is a doubt, just write to musikding, Klaus will send you your ICs. Then you will know for sure.

A popping noise following the Rate control, an extra Rate led...In my experience it's the main suspect, but i could be wrong.

Sorry i can't help you more than that, i didn't build this circuit.

Edit : it's always good practice to build the circuit with standard specs first, to make sure the build is fine. Then you can add mods. Makes it easier to debugg, at least you know if the issues come from the mods.

If you are in a hurry, you can restore your circuit to stock values, then add the mods progressively and see when this popping issue appears, this way you'll know exactly what caused it.