[ $2 ] DIY eurorack modular synth Wave Shaper with VCA / passive and few components

My 44th original eurorack modular synth DIY projects.
Nch MOSFET based wave shaper with VCA function.
It is passive module , so no need power supply. And only 2 parts.
working documents ( schematics )
note.com/solder_state/n/nfdc2...
Please support me to continue projects.
/ hagiwo
Cheap components list ( Japanese )
note.com/solder_state/n/n8ef0...
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See Instagram and Twitter for the development status of my next module.
Instagram
/ hagiwo_1
Twitter
/ hagiwo1
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[@MrGuillermofrancisco]

very simple way to become a HERO, thanks

[@chupathingy5862]

I just bought an electronics kit, this is the first module I'm building.

[@MeeBilt]

Wow! That's a really interesting module, thanks for sharing! 👍

[@bbs1369]

Very good quality video thank you - especially like the music. And a great module. Plus I like the power and ground connection strips on the back of your panel, have not seen that before.

[@sonosus]

Nice! I might just have to try this.

[@imnobody303]

An easy nice to have ! Thanks !

[@stefanhansen5882]

Amazing! Thanks!

[@saturn_at_sky]

a very interesting Module. but the front panel alone costs more than 2 $ 😉

[@HAGIWO]

Yes. I ordered 40pcs front panels at a time, reducing shipping and initial cost.

[@mubo144]

THANK YOU!

[@DekoBoyR]

music for the breakdown part?

[@hervelaporte1]

Hi Hagiwo. Can you confirm me that the CV jack should be connected otherwise the pot is not usefull to modulate the shape and module can not work well ? Thanks

[@HAGIWO]

Since this module is passive, voltage must be applied to the CV.

[@accordioncrowedrecords_]

I'm building this with the 2N7000, but the VCA does not work, there is still some signal present. The wavefolder function is fine and looks exactly as it does on your oscilloscope, but this VCA is eluding me. Is it possible the VCA function does not work properly with the alternative to the 2N7000L?

[@accordioncrowedrecords_]

Regardless, the wave folder function is spectacular!

[@HAGIWO]

The function of the VCA is affected by the output resistance of the oscillator at the input source and the input resistance at the output destination. Try several different oscillator and output destination modules.

[@u_peey]

I bought exactly same components, but my build doesn't work :( I tried to change parts and I surely checked all the thing, but still can't manage this to work. Maybe I did something wrong

[@HAGIWO]

It is affected by the impedance of the module on the input side and the impedance of the module on the output side (e.g., VCA or mixer). Try several module combinations.

it is possible to use 2N7000 or some alternative?

[@HAGIWO]

2N7000 is possible!

@@HAGIWO thanks much bro , your work is awesome !!! i want to build some modules inspired by you but i dont read japanese :D will you plan to have your blog in eng?

[@HAGIWO]

@ Try translating with google translate or deepl. thank you!

[@MidiFister]

@@HAGIWO people can open with chrome and it should offer to translate automatically - not all browsers do this

[@Gin-toki]

Have you experimented with different kinds of mosfets too hear how it affects the design? I would imagine different parameters would have a lot of influence on this. Also an extra idea, depending on the mosfets RDSon resistance, it could be combined with a capacitor of suitable value to make a simple passive lowpass or highpass filter when used in the "VCA" mode since here the mosfet works as a voltage variable resistor. The capacitor could be mounted with a switch to change between off, lowpass and highpass.

[@samueldyer4100]

Could you give more detail? I'm making this this and would very much like to add this functionality.

[@Gin-toki]

@@samueldyer4100 Search up "RC low pass filter" to see how a typical one is wired up. And also search for Passive Low Pass Gate, they are typically made with a Vactrol instead of a MOSFET but both can work. This should provide some info on how it works and is wired up. To convert this circuit into a lowpass when it is used as a VCA (reverse signal order) simply connect a suitable capacitor from signal output and to signal ground. When the resistance of the MOSFET changes with CV, so will the cutoff frequency of the RC filter change and you get a simple variable low-pass filter. For a highpass version, the MOSFET and capacitor needs to be swapped around, so the capacitor is in series with the signal and followed by the MOSFET to ground. The capacitor value should be selected based on the MOSFET on-resistance, since this determines the filters frequency when it is fully open. For this MOSFET which has a rather low on-resistance of a couple of ohms, I would guess a capacitor of around a couple of microfarads would suffice. say 4.7uF. For a non-electrolytic capacitor, this is a rather large value, so you are most likely going to need an electrolytic type which are also polarised (have a + and - leg) so in the low-pass case, connect the positive leg to the signal side and the negative to ground. And in the high-pass case, connect it in series with the signal where signal in goes to + and out from -. Most importantly, experiment around and have fun :) It is not guaranteed it will give a good result due to how the MOSFET has such a low on-resistance, which is why Vactrols are typically used for passive lowpass gates, due to have more suitable resistance values. But it is simple to test and verify since you are already going to build this circuit anyways and it only requires a capacitor to convert it to a filter. And a switch to make it selectable.