Monday, February 4, 2019

ReneDSR: Fastest Envelope in the West, Finished; Sound file and Build Notes

Back Again!

I needed more ADSR's in my modular so I built some based on a very cool design from Rene Schmitz.....You may want to read part I of this post here., where I create the PCB, discuss what "Tau" means, show you useless bench build photos, and so on.
Left to right: finished modules: ReneDSR, Return of Son of ReneDSR, and Son of ReneDSR

Not just Decay....."Fastest Envelope in the West"--by adding a switchable "YA" cap the entire ADSR gits along, little doggies

Does capacitor size matter?  

That's the "rayson d'tre" for these builds, but?? From last time, the basic design of these sorts of ADSR's sends gate logic to an RC circuit.

Good news: 

OK we've already determined that the size of the resistor and cap (the resistor being a pot and/or a resistor network) determine attack, decay, and release speed. So, should we build these with large caps and small pots?  Small pots and large caps? I think the jury is still out, because to me it all feels and sounds good. You can mix and match caps and pots here and have fun; the sun will still come up the next day.  And, set up right, either combo can provide mix-cutting, DJ boogeying, MDA popping sweaty-bodies-dancing-w/-body-odor bodacious snappy synth decays.

I tried to create a very simple demo for these modules, and you can hear sound samples here.

About the sound sample--other than the WAV loops this is all my modular with ReneDSR:

00:00: multitracking 6 mono notes on a DAW (Ableton Live 10). Attack time is set to minimum; release is set to max; it's a very fast attack (I didn't measure it on a scope, but you can hear, IMO anyway, it's a reasonably fast attack) with 23 second decay for VCA, and same for VCF.  I put a lot of rez on the filter to make the sweep more noticeable. You're hearing a 10uF cap and 2.2M audio taper decay pot creating the ever import tau (see the last post).

From this I get an MiniMoog's long release (>20sec) or maybe a Prophet 5-ish sound. I am happy.

00:33: Dual Osc bass line, maybe a bit of a Stevie Wonder? I always like that; Stevie and the late great George Duke are my all time favorite synth bass players. I remain happy.

00:55: Sequencer patterns. This is 2 sequences overlapped, making heavy use of ReneDSR's fast decay, without which the moving patterns sound mushy. I am not a big Gorgio Moroder sequencer guy but I know a lot of synth freaks out there are and for this application the ReneDSR performs well.

01:44: Single Oscillator to VCF to VCA, with SonOfRene controlling the VCF and Return of Son of controlling the VCF cutoff.  In many mixes I find that a single OSC bass sounds sit better than dual or 3 osc basses. Maybe a bit Roland SH series sounding. Why not?

The Roland SH-5 has one of my all time favorite ADSRs.  From the shop manual, it's a pretty simple discreet design from those crazy and creative 70's Roland dudes, so a PCB maybe for a later build?

The Return of Son Of uses a 2.2uF cap and 3x dual gang 1M audio taper pots. Each switch selects very good control of a 1M audio taper pot; or, tap off the wiper of a 2M pot. This allows for a good fast attack and decay with a longer release as needed.
Return of Son Of RenayDSR Switch Wiring.

Another build idea: In any Rene 2.2MB pot build, you might want to put the 2.2uF cap on a DPDT switch with say 10uF cap for longer decays and releases.  Or for 1MB pots, a 4.7uF and a 22uF.  Experiment and have fun! You get the idea.

Front Panel didn't come out very well for ROSO, lumpy and bumpy, but it's good enough.

The other 2 units--ReneDSR and Son Of ReneDSR--are pretty much a straight builds of Rene's two design variations on his site.  The 1U device has 1MB audio taper pots for ADR and a 4.7 and 10uF cap on a DPDT switch with 100ohm resistors in series. The second unit was featured in this post, and uses 2.2MB Audio taper pots, which can be a bit hard to find.

One more tidbit: Rene's design calls for CMOS 555 timer chips, I bought about 10, and couldn't get a single one to work in the 3 circuits you see here.  A standard 555 worked every time. So they may be something wrong with my PCB, or maybe I got a bad run of CMOS chips. Whatever--gotta move on.

Overall, a fun build, and more good sounding ADSRs were very much needed in my rig.

So if you're looking around for an EZ ADSR that performs well, and is fun to build, this may be it. FDITW is highly recommended.

And as always, don't breathe the fumes!


  1. Hi!
    Love the look of this EG and have built the majority of it already.
    Stupid question (because I'm kinda new to electronics) but what voltage do you power this with and what voltage is expected for the gate CV?

  2. I power my circuits with +/- 15V, but for this design I can't see why +/- 12V wouldn't work.

    Gate voltage needs to be a diode drop or more above ground, so anything over about .8V relative to ground should work. In my setup, 5V above ground is what I use for Gate and works great.

    1. Ah that clears up a lot, thanks!

  3. I also thought it should work better with log pots... I built it with 1MB pots... Did you use the 1M histeresys resistor??

  4. Alejandro: I don't use it on my own synthesizer setup, but, the resistor you are looking for is R12 in the board layout I show here and on my website.

    If you want to activate the hysteresis resistor, put a jumper between the pads on the top left: "1MSW" and "1Msw2".

    You can also put an SPST switch between those 2 pads to turn the hysteresis feature on and off.


Bluetooth Bench Mixer

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