Typhoon hardware has bleeding into output from CV modulation channels

[simodrws]

Dear Jak,

Thanks for the great design! Absolutely love the Typhoon. Here is a possible hardware bug I noticed:

If you put an audio rate signal (a square wave in my case) into the following CV ports, you hear it bleeding through to the outputs, even if the OUT VCA is turned down completely:

From loudest to quietest:

1. AUX in
2. OUT VCA
3. DENSITY
4. SIZE
5. TRIGGER
6. TEXTURE

The other CV ins (e.g. the different blend parameters) are unaffected.

This is not a problem when you use the clouds as a delay/reverb unit. But as soon as you start using the density parameter to increase the speed of the audio grains, you hear it in quiet parts when density is in the middle and the oscillator is modulating other parameters (e.g. AUX or TRIGGER).

This is especially bad because triggering the clouds with an audio rate signal is great for creating snare-roll like chordal pad beds & textures.

I have no idea about electronics but the guy who built it for me is TuneFish Modular, a (semi-) professional builder from Germany. He tested it with the MicroCell aswell and he experienced it too, although way quieter.

SuperCell was not available at the moment to test.

Now I wanted to ask: Do you have the same problem aswell with your typhoon/Cell builds?

Is this a design problem or a matter of wrong assembly?

Regards from Germany, Simo

EDIT: If needed, I can attach a video to showcase the problem.

[TotalRefusal]

Hi there! Any response to that???

[jakplugg]

Sorry you are having trouble! A bit of control bleedthrough It is kind of expected on the non-trimmable output VCA, and mine does it as well, But i can not hear any of the audio square wave (about +-4v) when i connect it to another CV input. I am not sure what is going on! my Typhoon is made by calsynth and has the Slider LEDs and drivers. The circuit is the same as microcell, apart from the layout and the LED drivers op amps.

[jakplugg]

Are you hearing the whole square wave or just the transients? if you input a sine wave and you can not hear it, that might help narrow it down.

[simodrws]

I am hearing with a sine aswell although way quieter. I will add a link to a video soon.

• bridging the LEDs (taking them out of the circuit), the sound disappears
• our suspicion is it's the conductor paths of the LEDs

[simodrws]

here's the video:

https://drive.google.com/file/d/1vxSAUuN0tCY1LKijelGPFKnqjkUx-H_d/view?usp=sharing

[forestcaver]

Tried this on mine (just finished it today). Copied what you did in your video. No bleed whatsoever on mine, checked it on a scope as well - nothing at all.

Just a thought - it may be worth checking what opamps are used to drive the leds - check you’ve used tlv272 and not tl072....

[simodrws]

Tried this on mine (just finished it today). Copied what you did in your video. No bleed whatsoever on mine, checked it on a scope as well - nothing at all.

Just a thought - it may be worth checking what opamps are used to drive the leds - check you’ve used tlv272 and not tl072....

which filter beads (L1 & L2) did you guys use? @jakplugg @forestcaver

We are waiting for the tlv272 to be delivered!

[forestcaver]

Hah! I’m guessing it was tl072 then? :-)

Ferrite not too important - just helps reduce noise from this module to other modules. I used these (I think) mouser pn:

710-742792664

same as in rings and most of the mi stm32 builds...

[simodrws]

yeah same here. lets see if the tlv272 make a difference!

[simodrws]

hey, little update:

tried the tlv272, same thing.

the behaviour i showed you also happens when the module is disconnected from power.

signal bleed is about 25 milivolts in power.

when physically seperating the led drivers (desoldering and bridging), the bleed is gone.

really weird.

[jakplugg]

what if you just pull the LEDs out of the faders, does it also go away?