Jtommi's first modular - Progress

If memory serves then @BlackDeath mentioned a superb tolex type paint that looked amazing.
Can’t find a ref on the site (I looked @Caustic , honest)
So, case is built! JFDI accreditation is in sight.


Tuffcab! Best stuff in the world. Tuff Cab :: Tuff Cab Black 5kg (Matt) £42.50 IN STOCK (11 Jan 2021) One bucket covers everything you could want. Get a foam roller!


Think its safe to say I have plenty of room for some LMNC panels on payday :rofl:


I went with a “wood stain with polyurethane” for my case. The poly seals up the wood good, but it may or may not be the look you go for and it stinks for a while so warning about that.

The poly also gives the wood a smooth finish. Either way you want to sand it up good and at least use a primer paint (i have heard non latex).


As im using wine boxes im toying with the idea of making up some shellac and doing some french polish. Any excuse to make denatured alcohol (which is really expensive and restricted in the uk and sold in giant cans in the US- very jealous)


What’s the benefit of doing that over a poly stain?


Absolutely none! But if you’ve ever made a guitar or violin or other instrument by hand there is no better and classier way to prepare a finish.

I built a cigar box reverb and DI unit for a bass player pal and used shellac to blend it into the colour and age of his double bass. Practical? Hell no! But very pretty and to this day some engineers ( who will remain nameless) still believe it was made in 1890.


While I’m waiting for my VCO PCBs to arrive, I’m drawing schematics in Kicad and start trying them.
I went for the Simple envelope

To build the breadboard, I went from my own schematic in order to validate it for later PCB ordering

I don’t have 1µF non polarized caps and I also don’t have 1M pots.
So I put a 100nF in and triezd with 1M resistors as well as a 100k pot.
I don’t see any change unfortunately, the LED reacts instantly (at least I perceive as such).
On the drawing Sam wrote "Smaller value = shorter envelope times.
So I guess 100nF is just too small to notice.

Can someone confirm that?
(the attack pot is missing on the breadboard)

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Here’s my attempt at the schematic if you want to compare:

Looks the same, just way more readable.
In order to get a 1µF I’ll try this: Can you make a non-polar electrolytic capacitor out of two regular electrolytic capacitors? - Electrical Engineering Stack Exchange


You probably have tons of 100nF (like everybody here :slight_smile: )
Why not put a few in parallel ?
10 will get you the required 1uF,
but 4 (for easy breadboarding with the 5 holes per strip) should be fine to test the circuit.


Of course I do, because someone told me to get them :smiley:

So I put 10 100nF in parallel on the + and minus strips of a different breadboard and than hooked that up with jumper wires.
With a 1M resistor on the attack, I could see an effect (<1sec)
I put 24 caps in parallel, put 1M+640k on attack, and I only roughly get 2 seconds attack (according to the LED, I’m using it without input and output for testing, only the push button).

Am I doing something wrong or is this basic EG supposed to only have this short times?

See, they are useful :slight_smile:

I never built the simple EG, but that looks really short to me.

2 seconds attack is really pretty slow.

The time constant you should expect is R times C. R is the resistance of the pot and C is the capacitance. You can use R in ohms and C in farads, or R in megohms and C in microfarads. With a 1M pot and 1 µF cap, as shown in the schematic, you should get an attack time of about 1 second. With 24 100 nF caps in parallel you have 2.4 µF so that would give a maximum attack time of about 2.4 seconds, which is just what you’re reporting.

Typical acoustic instruments have attack times of maybe tens of milliseconds. If you really want attack times greater than 2 seconds you need fairly big capacitors, e.g. 10 µF with a 1 M pot for maximum attack times ~ 10 seconds.


Thanks for the theory.
I’ll try the trick with two electrolytic back to back

I am very enthusiastic about the discussion of cases and finishes. I’ve considered General Finishes milk paint then polyurethane. It seems to work with guitar bodies so I expect it to work with modulars.

-Fumu / Esopus


Id love to see how it turns out.


So I received my AS3340 PCB and soldered everything on it.
Measure voltage before plugging ICs in.
Put ICs in, hook up tto speaker and a short blip and than nothing.
Turned out my speakers have a defective cable.
Connected other speaker, worked.

Then I took my Keysstep and started tuning.
After 5 minutes I gave up.
Then I looked at the schematic if I did an error and indeed I did.
I connected the 5k6 to the 24k instead of connecting it to pin 3 of the AS3340

So the bad news is that I have 5 “defective” PCBs.
Good news is that it’s easy to fix, I’ll desolder 5k6 and solder it directly on the 10k pot which has exposed legs.
And I’m actually pretty happy that my first ever PCB only has a small error.


Great job for a first go. Will you be correcting the gerbers?

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Yes, already done