DUINO Wah

[Eb7+9]

mixed-signal bliss

https://youtu.be/YoxyRGNwzes

a precision controlled State-Variable filter
requiring no external matching

// no mess, no headaches ...
PWM splash

[ElectricDruid]

Right up my street! Excellent work.

Tom

[stonerbox]

Stepped controlled wah!? I want this bad but programing is not one of my skills.

[Eb7+9]

I'm very lucky to have Tek465b doing code for me ...
he whips the sh*t up like it's nothing
wrote this one on his phone lying on the couch watching tv

I'm sure there are many young peeps around who can figure this out,
and come up with their own version

give it time ...

FYI, next version of our code will see a control for setting the amount of "stepping"
from none (continuous) to full-on Sample-hold type stutter ... we'll see

---

so, here it is ... the "other" outcome of my PWM-gate characterizing work I started last fall

this last round of tweaks showed me how to make best use of this RMS-resistance technology ...

as I posted earlier the bottom 10 steps can easily be perceived due to their spacing between values
the first two are worse, in this case jumping from Requiv(0000001)=400k to Requiv(00000010)=200k
last position goes down to Requiv(11111111)=400r ... with grain getting finer as we approach the low end

in this case I found it advantageous to skip or throw away the first 10 steps
and ride along in the part that sounds continuous to the ear ...

10 steps out 256 is about 3.9% of the range ... minimal

I then adjusted the CMOS state-variable filter caps to slightly higher values to compensate for the difference
there was more than ample top-end range after the switch ...

so, it would appear that the total Requiv range in this circuit, as I have it running now, is 400r to 40k
this could be verified easily by using a dual 100k pot  (... manual version of the circuit)

---

two years ago I posted a video that showed how to optimize the bias of the MXR Envelope Filter
I noticed it wasn't a much studied circuit, and became curious about its potential for extension ...

https://www.youtube.com/watch?v=lDeW-wDtflw&t=378s

there is  no doubt it is a marvel analogue circuit design ...
one of my fave pedals, wish I knew more about the person behind it
(anybody know the patent number pls post it ...)

---

fast forward a couple

with the help of Tek465b I was able to extend the operating minima of the PWM-gate'd CMOS filter to 0.39% duty cycle ... producing an effective Requiv of 400k using the CD4016 IC, without any series resistance that is

the original MXR circuit idled at its lowest positioning of about 5%

the 5vdc Arduino environment is also very friendly to the CD4069/CD4016 IC's I'm using here
and leaves well enough headroom ...
I suspect there's still enough linearity available in the 3v p-p range, at east for gizmo applications

with a tweak to the CMOS filter circuit that adds a synth-style EMPHASIS control
this is what I got

https://www.youtube.com/watch?v=rX8M5-hLbes

at the moment I'm running the CV off a mccon-o-pot ... but will be switching to Boomerang 50kLOG shortly

otherwise, I'm very pleased with this PWM-gate technology ...
especially after discovering the benefits of using the (simpler) CD4016 over CD4066

noise specs are fabulous, headroom is good ...
had been mulling over a good active filter for a long time