Dual-Filter Dual-EF soundclips

[strungout]

And some pics! 




It fits!


Quick Demos of some interesting sounds:

Yoy. Sweep of the Hi-Filter Down, Lo-Filter Up.
https://on.soundcloud.com/W5FQt

Both sweeps up, bandpass and non-inverting dry signal.
https://on.soundcloud.com/1oejz

Little bit quacky.
https://on.soundcloud.com/tUpJX

If you listen carefully it voices 'LOL'...
https://on.soundcloud.com/VESab

[idy]

Wah to end all Wahs. Satisfying number of knobs. Tells us more. What is the basic filter you are using? Did you share this on another thread? You said something about non-inverting dry signal, are you able to change phase? I've found that in/out of phase dry/wet gives some good choices. I guess BP is usually the non-inverted one, right?

I've tried using two mutron clones with a splitter blender, but I really need blend and some other controls to make it less obvious. Maybe two meatballs...

[ElectricDruid]

Nice!

Those are VTL5C3's, so those look like optical state-variable filters. I used the same design for the Druid FilterFX because it's easy to control and the circuit is simple and the headroom is good, so it's not noisy.

What did you use for the envelope followers?

[Mark Hammer]

I dunno, Frank.  It may need a few more controls.     Are you familiar with Marjan Urekar's "Fuzzyballs" - a full-featured extension of the EHX Bass Balls? https://urekarm.tripod.com/synth/fuzzyballs.html  He might have a few more controls than you do...but not that many more.

In all my filter builds, with the exception of the original MXR Envelope Filter, I find that including an Attack control creates more headaches than it solves.  Because it is generally a variable series resistance, a) the resistance range it would have to cover to provide noticeable differences in attack time is too big, and b) that series resistance reduces the drive current feeding the control element, such that any change to Attack requires an adjustment of Sensitivity.  So, I just include a Decay time control, which avoids those issues and still provides usable and noticeable sonic differences.

The "talking filter" produced by countersweeping two filters is nice.  Although digital, the Line 6 Otto Wah also has such a mode.  Jeorge Tripps hipped me to the "easter egg" in the pedal that, if used in a stereo dock, each filter goes to a separate output, such that any triggered sweep seems to move across the stereo field.

One of my projects "on the stack" is a counterswept dual filter, although I'd like to be able to modulate them via independent LFOs or envelope follower, although something like Ken Stone's "Psycho LFO", that uses a 40106 to produce a semi-random stepped CV might be interesting.  Imagine two parallel S&H filters, and that should give you an idea.

Another thing I'd like to play with is being able to adjust the width of the passband.  I built and sold a DOD 440 clone several years ago, and rather liked its' more vocal quality, compared to other swept bandpass filters.  Some of that is the specific filter topography, but the passband just struck me as a bit wider than many, resulting in a less quacky sound.  So something that allowed one to have a cascaded pair of 2-pole filters, one high-pass and one lowpass, with the lowpass adjustable, via toggles or pot, to provide for wider and narrower passband, might be nice.

[strungout]

Hey guys,

@idy: they are both state-variable filters, as Tom mentioned. Basically, it's two Mutron IIIs, set for high and low sweep. There are three caps selections for each. The Dry signal can be inverted, non-inverted or off. It comes from a mod Mark made to Craig Anderton's Bi-Filter Follower, where it created a bit of phasing along with the sweep. I think it's working, the sweep can sound somewhat more 'metallic'. It works only in bandpass (both), which is non-inverted and then mixed with the inverted dry signal. There is a little bit more info here: https://www.diystompboxes.com/smfforum/index.php?topic=130429.0

And the schem I ended up with:



@Tom: thanks! My fave EF is really the MXR (that's the one I used in my 'multi-wah' project, feeding the signal to your awesome little stomplfo chip's offset pin), but to make the build simpler I just used two Mutron IIIs, as said above. I'm not sure if and how much bigger the boards would have been with the 4069s...


@Mark: MOre knobs! More knobs!
Yeah, you shared M. Urekar's Fuzzy Balls before.  I might build one at some point, just to play around with it. I decided not to add stereo output because of space concern. That 'easter egg' sounds cool, I'll go search online see if I can find a clip or something...
I love the sound of a stepped filter. At some point, I thought I would build another of my 'multi-wah' (which has random steps from Tom's chip) and just parallel the two. But, I wanted it all in one box, seemed more convenient. And two multi-wahs would have made it a rack thing, at that point, haha.
I'll breadboard a DOD 440, see for myself


The only thing that bothers me a bit, a bit, is that the cap selection switch goes mid/hi/lo. I marked it on the graphics but my brain still thinks up is highest...