Let's Design and Build a (mostly) Digital Theremin!

“D-Lev World Industries?!?” LOL! Go get ‘em! Take on Big Tech and put ‘em out of business! Hahaha!! Go get ‘em!

"What I'd love to know is when a kit might be available, and the details of ordering one."  - robedney

Thanks for your interest!  You can contact me via the email address in my profile.  I'm not entirely sure where it's all headed, but I can certainly keep you in the loop.

“D-Lev World Industries?!?”   - ContraDude

We're a modest worldwide industry (with much to be modest about).

How much are your kits? Very nice design..is your volume responsiveness user definable?  I haven’t seen many videos of your theremin but the one I saw all demonstrated it’s very good staccato response.  Are there good examples of more subtle volume changes?  Thanks 

"How much are your kits? Very nice design..is your volume responsiveness user definable?  I haven’t seen many videos of your theremin but the one I saw all demonstrated it’s very good staccato response.  Are there good examples of more subtle volume changes?"  - Yngvox

There are a bunch of videos I did during development here: https://www.youtube.com/user/wildlavarice/videos.  One thing the project could use is more videos, and I'm hoping the kit buyers will do some of that work for me. :-)

Volume field processing (linearization, sizing, location) is essentially identical to the pitch field processing, and the goal is to make it linear, then introduce a gain break point - or knee - in the response, which you set the location and strength of via knobs.  This is a downward expansion below a certain volume, which is the same way an audio expander works.  There is also an envelope generator with velocity sensing.  Combining a sharp (high gain) knee with velocity gives you a controllable percussive attack for the envelope generator to chew on.

You can contact me via the email address in my sig regarding the availability of kits.

D-Lev Kit-in-a-Box Videos

When one of the kit buyers dropped by my house to pick up their kit, I found myself prattling on about a bunch of stuff that all of the kit owners should probably know up-front.  So I made a short series of very short informal videos showing the unboxing and setup, and thought I would share them with the folks here at TW.

1. Unboxing and reboxing.
2. Electrical interfaces.
3. Hooking up the antenna plates and DAC box.
4. Physical setup, plugging in, ACAL, pitch field calibration.
5. System profiles.
6. Sculpture mode.
7. Pitch correction.
8. "Rock of Ages".

https://www.youtube.com/watch?v=eTSsM8V0IT8
https://www.youtube.com/watch?v=h7JtbgNa-Gs
https://www.youtube.com/watch?v=TfCsbfzvfoc
https://www.youtube.com/watch?v=fYuB8CqhmAE
https://www.youtube.com/watch?v=WfS3JAgU1kA
https://www.youtube.com/watch?v=LfIJ22oH7bc
https://www.youtube.com/watch?v=gJCOpT-Evr0
https://www.youtube.com/watch?v=MPdWvXUokSE

These are extremely informal, done in one take, with the sleazy cam software in Win10.

I need to make a few demonstrating the librarian software for users too.

[EDIT] And, as I stated above, all of my videos can be viewed here: https://www.youtube.com/user/wildlavarice/videos

D-Lev Librarian Videos

Some new rough (a few verbal slips here and there) videos demonstrating the use of the D-Lev Librarian:

1. Introduction.
2. Performing a factory reset.
3. Performing a full backup.
4. Performing a full restore.
5. Live editing (remote control).

https://youtu.be/geE4j6yXacU
https://youtu.be/PZHyI4Wl8FU
https://youtu.be/JJQIU1TjyiE
https://youtu.be/cUeACROBZGY
https://youtu.be/stOQl2NN1RY

I think folks here would find the last video the most interesting.

The librarian started out life as an underdone assortment of wobbly Tera Term TTL scripts.  I'm actually rather proud to say that it has finally achieved a sort of seedy half-baked status as a hodgepodge of C++ spaghetti code tenuously supported by a sketchy cross-platform scaffold wrested from the cold dead hands of various terminals.  Hey, at least it's open source (so others can experience the full horror of gazing into the dark abyss of its code base).

[EDIT] Just revamped the D-Lev web page some to include embedded video and audio players.

Rising Damp

One of the kit buyers expressed a possible use for the bell voice presets in the D-Lev, and during that discussion I explained that - other than switching presets - there was no way to damp them once played, as the long decays are based on filter resonances; though voices which rely on the envelope generator for sustain can certainly be damped.  Which got me to thinking that I could probably employ the envelope damp control as a filter resonance multiplier too.  So for the past couple of days I've been messing around with implementing that. 

Of course, the activity prompted yet another parameter type system overhaul - this time a fairly radical reduction in generics and a slight expansion of special cases.  You want a range of general knob scalings during development to ease / speed up the search for the most appropriate (the most usefully distributed range spread over the smallest number of detents).  But many get abandoned, and it's a good practice to cull them once development winds down because it frees up some code space, which is a little tight on the D-Lev.  And it simplifies the code base somewhat, making it easier to maintain later.

I was able to get the damp knob detent count down to 32 with a rather convoluted scaling: full scale, ^4, 48dB exp2, pull down to zero, bit invert.  You never really know where you'll end up when scaling knobs!  I probably should have spreadsheeted it and saved myself some time / gained some insight, but it seems fine.

Here is a sample of some of the percussive patches being actively damped via my volume hand location (top of the page): https://d-lev.com/audio.html.  The usual suspects (same ol', same ol' presets) but this time with DAMPING!  Which can be used to interesting effect - the damped 6" triangle at the end would fit right in with a 70's heist movie...

This exercise made me realize that the volume field could use a pre/post envelope generator display option on the tuner, much like the pitch field already has for pre/post pitch correction.  In fact, pre-envelope rather than post should be the default, contrary to the way the D-Lev was operating.  You are usually much more interested in where the Theremin "thinks" you hand is, than the result of that (though they are pretty much the same when the envelope generator isn't being called on to do much).  It was a fairly simple thing to expand the Post[0:1] knob to Post[0:3] and give the user complete control over the display of pre/post of the processing of both fields on the tuner.  And the default Post[0] is to now show both hand positions pre-processing.

It's always nice to make improvements to the basic operation!  No such thing as too much code polishing IMO, there's always a way to improve it - even if your audience can't perceive it directly, they'll likely appreciate it indirectly.

And The Answer Is None.  None More Black.

I'm trying to simplify the D-Lev field calibration instructions / steps in the manual, and I think the pitch side pretty much done.  But this exercise on the volume side is making me realize there is yet one more nail in the traditional volume sense (farther = louder) coffin. 

For closer=louder you set 0dB (maximum loudness) a little above the antenna, then inaudibility ends up somewhere above that.  If you want it quieter you simply pull your hand farther away.  0dB is well defined, so there are no issues in positioning it.

The problem with using a linear field as the basis for traditional volume sense is: what exactly is inaudibility?  -48dB?  -96dB?  It actually varies depending on a lot of things, such as the current pitch, the harmonic content of the voice preset timbre, the dynamic range of the player, etc.  Unlike 0dB it is a vague / subjective thing.  If we place -48dB right at the antenna then the player might end up hitting the plate in an attempt to quiet it, which I guess is why the volume antenna is a loop on most Theremins.  If we place -96dB at the antenna then -48dB (what I think of as general inaudibility) will end up centered between the plate and 0dB, which could be quite high up.

The D-Lev knee comes to the traditional volume sense rescue here, expanding the volume at the plate down, enabling a smaller and more manageable volume field size.  But it is a per-voice parameter - as it must be because it can be used as an effect - so voices that don't use it may experience volume leakage.

Traditional volume sense leverages the tight non-linearity near the antenna to deal with this and form a natural volume knee.  I believe that's essentially why Theremin picked it.  But it doesn't transfer well to linear fields.

Stencil Fun

Making 3D printable stencils is fun and easy with OpenSCAD:

Thanks to Charlie Draper for the clever pun!  Any future kits may have this spray painted on the inside lid.

Dewster > Thanks to Charlie Draper for the clever pun!  Any future kits may have this spray painted on the inside lid.

Will the next set of Clarabox kits be the Sesquicentennial Plus 1 Year Edition? 🤪