Completed: D-Lev Digital Theremin Prototype PIII

Posted: 5/16/2021 8:29:16 AM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015

Thanks Dominik! 

I would love to read an article about how you build your Subscope cabinets, if you were so inclined to share that information here sometime.  As you know I have always been impressed by the design and attention to detail of the one you built for me, right down to the custom labeling and the built-in storage for the adjustment screwdriver.  For a while I was searching all over the country for some of the flaked and quartersawn Beech of the type that you chose for the top, bottom, and ends, but I never found any at the time. 

I'm also intrigued with your use of a photo tripod to support one of the other Subscopes that you posted a picture of here on TW. The D-Lev with its encoder push buttons really needs something like that.

Here's the wood from the top of my Subscope (the flake is unfortunately washed out with the flash).  I'm assuming that this is a hand-selected piece because if this is your average European stock then I am jealous :

Posted: 5/16/2021 10:43:51 AM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015

More on this PIII version of the D-Lev

If it sounds like I'm bragging up this latest D-Lev too much, let me balance that by listing a few pros and cons of both the D-Lev design and this particular version of cabinet layout.

First let me critique my own hardware/cabinet implementation:

Pros:
1) While it's the least interesting of the three designs that I've built so far, the layout and visibility of the controls and the tuner make it the easiest to use.
2) The touchless mute is sweet!
3) It is quick and easy to set up and attach the antennas without tools.
4) It's easy to get inside and work on it while turned on.
5) It was designed to be fairly easy to build.
6) It's done and it doesn't look bad!  That in itself is a worthy "pro".

Cons:
1) I don't like high-gloss plastics that are often used with electronics as with the D-Lev's front panel.  The best it ever looks is right after you peel off the protective material.  Fingerprints and scratches are inevitable, although theremins don't need to get touched very often.
2) This is definitely not "production quality".  It is hand made and doesn't look as sharp as something produced in quantity in a factory environment.
3) I'm not at all happy with this horizontal layout when used on a standard mic stand.  The encoder push buttons require enough force that the whole mount flexes.  I'm going to look into using either a photo tripod or a custom wood or metal stand.
4) I don't like the knobs that I used.  Finding suitable knobs is a problem, and I may end up printing plastic ones.  For the encoders you want small diameter knobs that are very grippy.
5) Short of putting on some basic stick-on labels I don't see any markings for the mute switch or pots in the near future.  It's not hard to remember the functions, and the eight encoder knobs would be unlabeled anyway.  But it does look a little unfinished.
6) I always fret over the length of the high impedance line runs to the antenna and the proximity to wood.  Plus the D-Lev analog front end has the low-Z drive near the high-Z sense line return, so separation of these always ends up being a compromise. In practice I haven't noted any problems with this layout yet.
7) Theremin grounding isn't as easy as plugging in a 3-prong wall-wart power supply.  A separate ground must be used.  I don't consider this a con, but I expect others might wonder why they have to do this.

And for the D-Lev architecture itself:

Pros:
1)  I can't even begin to praise Eric's D-Lev design here, but I will suggest that there is nothing close to it, and I would go so far as to include the Claravox in that assertion (based entirely on what I have read and heard). But I will list a few attributes.
2) Pitch and volume field configurability; not just 3 or 5 canned choices, but virtually continuous control over multiple parameters to shape the fields to the player's comfort.
3) Rock-solid stability compared to analog theremins:  a slight drift in the first 10 minutes, then you're good for hours.
4) Includes a compact but multi-featured synthesizer section that can create almost limitless voices and sound effects
5) Available pitch correction that is discreet and can help sweeten your sound against other accompaniment.  It's intended to put the theremin on more even ground with other instruments rather than cover up poor technique.
6) Pitch preview options for everyone.  Limitless options.
7) A bank of eight pitch- and volume-modulated formant filters to allow emulation of instrument bodies and human voices.
8) Two separate stereo outputs: one for the main audio and one for pitch preview, each with analog buffer stages and dedicated level controls
9) Auto calibration of volume and pitch "reference beat" using either an encoder press (with programmable delay) or foot pedal to activate.  You position your arms in the receded position and activate ACAL.  No fiddling with touchy knobs.
10) There is nothing to tune or adjust inside to maintain the theremin's performance.  The only adjustment is a contrast pot for the LC display, and this is set once during initial calibration.

Cons:
1) The user interface is built around a 20-character, 4-line display that identifies the functions of the eight "soft" encoders surrounding it.  Out of necessity the parameter names are limited to 4-character mnemonics which makes it not as easy to use as, for example, a graphic touch screen.
2) Initially I felt that there should have been dedicated encoders for the functions equivalent to the familiar "pitch" and "volume" controls on an analog theremin. I no longer feel that way, but others might.
3) This is a little obscure, but I feel that the mix or level of the inharmonic resonator effect should be able to be modulated by pitch and volume as are many other parameters.  The fixed level is always a compromise, but I understand why this can't currently be implemented.
4) I feel that all voice presets should by default have pitch correction turned off instead of on, except in cases where a few examples are grouped together.
5) I'm grasping to think of more cons; most of the issues and these functions have been hashed out to the point that I almost feel that the D-Lev is tailored specifically for me, even though there is something to appeal to almost everyone.

So with that, onward and upward.  Coming up next will be the unit that I build for Eric, which will be white with rosewood ends and should give his D-Lev that warm rich sound with great resonance and volume .

But back to promoting the PIII... Here are a couple "glamour" shots of the completed red model.  Images are by Becky Hart:

Posted: 5/16/2021 2:13:27 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Tell Becky "beautiful pix!"  What did she use for the neutral backdrop?

The Logo (nice!) looks like it's maybe 3D?

"3) I'm not at all happy with this horizontal layout when used on a standard mic stand.  The encoder push buttons require enough force that the whole mount flexes.  I'm going to look into using either a photo tripod or a custom wood or metal stand."  - pitts8rh

I realize the knob locations are rather baked in by the master PBW, but I was thinking (out loud) that one could maybe locate both columns of knobs to the right of the LCD?  This would position them more in the center over the mike stand mount, where there's more leverage to be had?  It would also address the adjusting hand obscuring the LCD.  But things would cramp up a bit too.  Just curious, how did you settle on the overall width of the case?

Would the mount benefit from a larger diameter interface at the wood?  Like maybe a fender washer between the adapter and the underside?

"5) Available pitch correction that is discreet and can help sweeten your sound against other accompaniment.  It's intended to put the theremin on more even ground with other instruments rather than cover up poor technique."

Au contraire! ;-)  It covers up all kinds of sloppiness, in my playing anyway.  I've noticed (for better or worse) that I use it to "form" the melody by quickly centering the notes, rather than via volume dips.  But when I'm off pitch I'm really off pitch - it's a bit of a high wire act - meanwhile my volume "technique" languishes.  (I really should develop a formal fingering technique rather than mainly using my wrist & arm - someday...)

"4) I feel that all voice presets should by default have pitch correction turned off instead of on, except in cases where a few examples are grouped together."

This is a "factory" preset issue, and I'm not exactly sure what to do about it.  Folks can certainly get fiddly and set things up however they want with the librarian software, but (except for voices that use hard quantization) the best initial pitch correction settings are a minor conundrum.  Perhaps you're right, that it should be off by default (maybe good to go, but levl[0] to defeat it).

"5) I'm grasping to think of more cons; most of the issues and these functions have been hashed out to the point that I almost feel that the D-Lev is tailored specifically for me, even though there is something to appeal to almost everyone."

You came on the project when the architecture was still fairly plastic, and you helped me immensely to implement pitch preview, the odd/all oscillator parameter, pitch correction, and many other features.  And you ferreted out issues with the envelope generator and resonator (the joys of being an alpha / beta tester).  So it actually was somewhat tailored specifically for you! :-)

Posted: 5/16/2021 3:12:58 PM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015

Tell Becky "beautiful pix!"  What did she use for the neutral backdrop? - Dewster

It was just taken against a beige wall.  The outlet and baseboard were removed and the whole background replaced in Photoshop.

The Logo (nice!) looks like it's maybe 3D?

It's vinyl in 2 colors.  I'm trying to use our 25 year old Stika vinyl cutter that only works on XP with an ancient version of Illustrator.  I have all kinds of cutting path problems that I've tried to fix in Inkscape but that's only been partially successful. Some later cuts have been better, but I should probably get a 21st century cutter sometime.

Just curious, how did you settle on the overall width of the case?

I used the Etherwave, Subscope, and my D-Lev "Pro" as references with a large dose of "whatever it came out to be" thrown in.

Would the mount benefit from a larger diameter interface at the wood?  Like maybe a fender washer between the adapter and the underside?

It's not the adapter flexing at the wood, it's just the instability of these flimsy mic stands.  But if you look again you'll see that there is already a fender washer in there.

Au contraire! ;-)  It covers up all kinds of sloppiness, in my playing anyway.

I haven't used it enough to feel comfortable with it, and I would rather never use it as a matter of personal choice.  Part of this is because I never perform (and never will); I only practice, and I don't want it interfering with practice.  There is no doubt that it works, but it would take a highly skilled player to make it totally undetectable. 

Perhaps you're right, that it should be off by default (maybe good to go, but levl[0] to defeat it).

That's what I do - if it's a preset that I've tried PC on at some point I'll just keep all the settings but turn it off with the level control and then re-save the preset that way.  The point I'm making about defaulting to off is you don't want someone to try out the theremin and have pitch correction interfering with a first impression.  I've run into that on factory presets (before I figured out that PC was on) and for someone like me that just starts playing on whatever note is in my head it creates all kinds of havoc when PC is pulling one way and then the other way.


Posted: 5/16/2021 7:40:25 PM
JPascal

From: Berlin Germany

Joined: 4/27/2016

It's incredibly interesting how the teamwork led to this great results. Thank you for the insights into all considerations, developments, implemented modules and last but not least into the craftsmanship. This looks like a real friendship between you both and the theremin technique.

Posted: 5/17/2021 12:53:25 PM
ContraDude

From: Basking Ridge, New Jersey, USA

Joined: 12/12/2020

Wow! What a beautiful instrument. Your attention to detail is fantastic! I’m really eager to hear how it sounds. 

While I’ve ordered a Claravox, at this point, I’m really disgusted with Moog and have no intention of purchasing anything from them again. The amount of detail pertaining to the features of the D-Lev is far greater than Moog has provided on the Claravox and it certainly appears that you’ve greatly outdone them with your design. Moog has provided relatively little information and, other than a few teaser videos, we know relatively little about the Claravox. 

Great job! I would certainly consider canceling my order for the Claravox if there was an alternative, such as the D-Lev, available. 

Posted: 5/17/2021 1:10:58 PM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015

JPascal: 

Nice comments - thank you. 

It was April of 2018 when I first approached Eric, so I guess that make three years that we've worked together on this.  It's been quite a symbiotic relationship because even though we're both EEs we have relatively complementary skill sets and rarely step on each other's toes.  Eric's willingness to listen to ideas and turn around and implement them with ease has made this work, and he should be proud of what he has done and hopefully the theremin community will soon benefit from it.

ContraDude: 

Thank you as well.  I share your frustration with the Claravox, and although I'm sticking with the order I'm sorely disappointed in the lack of pitch preview built into the unit.  Even though not everyone uses it, it's not a difficult thing to put in and I believe it's a major oversight to leave it out of a "pro" instrument.  I know I can add it in, but others can't and it just makes me wonder who is running this show over there.

Regarding the D-Lev, there should be a demo unit that will be made available soon on a loan basis to test the waters of interest.  Eric will manage how this gets handled when the time comes, and presumably there will be some (amateur) video demos and a detailed manual released shortly before the hardware.  I don't have any supply chain problems, and I have all the parts.  We're both just a little busy at the moment.  But please stay tuned.

Posted: 5/17/2021 6:36:09 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Roger has thrown his entire life into this labor of love for an extended period of time, taking on the task of alpha / beta tester, spearheading the PCB initiative, and exploring exotic cabinetry design. Many features in the D-Lev owe their existence / refinement to his keen insights and observations.  And now he's making the first demo units and editing the manual!  Roger's been an all around incredibly good friend and collaborator, and I can't imagine anyone on earth better suited to advancing this project!

ContraDude, now that my wife and I are inoculated (Wednesday will mark 2 weeks past the 2nd Pfizer shot) we're starting to let our quarantine guard down.  I'd be thrilled to have you over to our house (in Boonton, NJ) to demo the D-Lev and meet and greet and stuff!

Posted: 5/17/2021 9:30:07 PM
Mr_Dham

From: Occitanie

Joined: 3/4/2012

Code:
But please stay tuned

The case is beautifull. And the sound samples on D-Lev's website are beautifull too.
So yes, antenas are deployed and tuned

Posted: 5/21/2021 11:57:09 AM
Buggins

From: Theremin Motherland

Joined: 3/16/2017

pitts8rh,

How did you select top panel tilt angle? What angle you are using in your design? Is screen visibility good enough?

What is spacing between encoders? Is it feasible?

You must be logged in to post a reply. Please log in or register for a new account.