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

"The 4th badge appears like blue on white rather than black on white. Is it just my screen ?" - Mr_Dham

I think it's your screen?

"Other question: what are the dimensions of front panel and tuner?"

The front panel is 125mm x 165mm x 5mm high, with radius 6mm at the corners.  The mounting holes are 3.5mm located at the centers of the corner radii.  The mounting cutout hole is 105mm x 145mm and centered on the front dimensions.

The tiny tuner panel is 125mm x 80mm x 5mm high with radius 6mm at the corners.  The mounting holes are 3.5mm located at the centers of the corner radii.  The mounting cutout hole is 102mm x 61.5m and centered on the front dimensions.

[EDIT] I just posted all my OpenSCAD files for the D-Lev kit: https://d-lev.com/support/D-Lev_Kit_OpenSCAD_2021-07-18.zip.  Also added a News page to the D-Lev site: https://d-lev.com/news.html.

I just inkjet print the picture, and indeed, it is my screen. I think I should do a color adjustment on it, LOL.

Thanks for all the detail. It will be a great help to run my imagination on a box.

"Thanks for all the detail. It will be a great help to run my imagination on a box."  - Mr_Dham

I added some new kit pix to the D-Lev web page that might help put things in a bit more perspective (now with real hands!): https://d-lev.com/images.html

"Thanks for all the detail. It will be a great help to run my imagination on a box."  - Mr_DhamI added some new kit pix to the D-Lev web page that might help put things in a bit more perspective (now with real hands!): https://d-lev.com/images.html

Truly beautiful! It’s great fun watching all of this take shape. 

On a side note about the post that mentioned black ink looking a bit blue - I know that some black dyes (such as those used on leather goods) have a base that’s either blue or green. It’s possible that Sharpie ink may have a blue base, which might be evident under certain lighting conditions. 

Bollamin

Went ahead and mounted the kit in a 4 bottle wine gift box we had sitting around (actually held 3 bottles I think, but is the width of a 4-bottler):

Just screwed a couple of pieces of scrap wood in there that happened to be the same height as the depth of the box, and the width worked out better than anyone could have hoped for, requiring only thin cardboard shims keep the coil / AFE boxes in place.  Left a 10mm gap at the top and between the plates for cooling (not really needed).  UHF connectors for the antennas, using some rubber ducky types left over from my research years ago.  Just need to make the hinge pins removable somehow to get the top out of the way when playing.  It's rough, but is seriously semi-cool looking, like a spy attache or something...

[EDIT] and the reason I did this... I think this is a relatively ideal form factor for a Theremin.  The whole thing obviously needs to be angled forward somewhat, and the pitch antenna could perhaps be a 'T' type instead of this 'L' type form, and both with larger diameter to give better SNR.  But the above is something I believe I could seriously play long-term without feeling like anything is too compromised in the way of ergonomics or physics.

Real hands are great for perspective!

I definitely need to visit summer garage sales for wine boxes....

I am looking for a compromise in size and weight so as it fits nicely on a mic stand.

Do you have something specific in mind for the stand ?

"I am looking for a compromise in size and weight so as it fits nicely on a mic stand."  - Mr_Dham

The kit in this particular wine box weighs 4lbs or 1.8kg, including the antennas, but minus the SPDIF D/A box.

"Do you have something specific in mind for the stand ?"

A threaded metal plate would work.  I've been using these sorts of products on my prototypes, along with a boom mic stand with the boom fully retracted:

Show And Tell #3

I did another show and tell session yesterday, I won't say with whom in case they don't want to publicly comment.  But I though some folks might be interested in the setup in our music room:

That's Roger's white P3 on the left, the "Bollamin" kit in the center, a laptop to show the librarian and power the units, and my skanky lab unit on the right.  For sound we were using the speakers I designed for our digital piano, seen between the P3 and the kit (sats on top, sub on the bottom).

Someone once said: "playing a rod is like like walking a tightrope, playing a plate is like walking on the sidewalk" and I have to agree.  Maybe it's just years of playing plates, but with plates I don't have to pay very much attention to where my hands are horizontally.  I'm not saying plates are for everyone, and rods certainly make a lot of sense on an analog Theremin for linearity reasons.  And there is the historic expectation of the sight of rods on a Theremin, which I don't really know how to respond to.  If history were somehow reversed, and digital Theremins came into existence before analog, this argument would go the other way and people would be hollering at the analog guys for using rods instead of plates.  I'm not a big fan of legacy / backward compatibility / retro so I see these expectations as impediments to development and forward movement of the instrument, though I understand how one would like to accommodate someone's years of training on rods.  For the rod crowd, I'd recommend they give plates a fair shot, and if they can't acclimate to them after a month or so, try narrow plates or larger diameter rods.

There was a lot of electrical interference yesterday, probably due to the AC unit running up in the attic directly above our heads.  Of the three my lab unit was the most stable, which makes sense as plates give the best SNR.  And believe me, you often need all the SNR you can get when measuring femto-Farads in real-time.  I don't know how anyone has the stones to precision play any Theremin in a live setting for a large audience.

Anyway, if you're ever near Boonton, NJ and are interested in demoing the D-Lev, please contact me (email in my profile).

. . . That's Roger's white P3 on the left, the "Bollamin" kit in the center, a laptop to show the librarian and power the units, and my skanky lab unit on the right.  For sound we were using the speakers I designed for our digital piano, seen between the P3 and the kit (sats on top, sub on the bottom). 

You have a D-Lev museum!

I'm not saying plates are for everyone, and rods certainly make a lot of sense on an analog Theremin for linearity reasons.  And there is the historic expectation of the sight of rods on a Theremin, which I don't really know how to respond to.

Here are a couple of questions:

1. Is it possible to offer kits with both? Then let people play and compare.

2. I like the rubber ducky antennas  With a digital theremin, does the length of the antenna play a role in performance?

"Of the three my lab unit was the most stable, which makes sense as plates give the best SNR.  And believe me, you often need all the SNR you can get when measuring femto-Farads in real-time." - Dewster

I sense a creeping advocacy for plate antennas. This is one of several offline arguments (like octave fingering-spans and volume antenna sensing) that apparently will never go away, so let me be short and sweet (and public) with my opinion.

If you choose to learn to play with a plate antenna on the pitch side you will find that if you try to play other theremins with the more common rod antenna later you will need some time time to adapt your fingering techniques.  It may not be a big deal for you, or you may regret that you ever started out with a plate.  Much depends on the particular playing technique that you develop, as some will be more sensitive to the antenna differences than others.

If you are already a player with some experience with a rod-style of pitch antenna you will take some time to adapt to a plate antenna.  Nearly all of these differences are in the fingering techniques learned for intervals in the near-field or upper pitches.  This is to be expected because the closer you get to the antenna the more the field lines between the two antenna types become dissimilar.

While I recognize that plates do provide a higher signal-to-noise ratio (better for electrically noisy environments), I never got past the point of a pitch plate feeling a little "off"  and from day one I set out to validate the use of traditional rod and loop antennas on the D-Lev, both for aesthetics and for ease of transition for existing players. In my testing with several different prototypes that has been accomplished.  I feel that if the analog theremin can work satisfactorily with traditional rod and loop antennas, then the superior digital theremin should do this at least as well. I think the D-Lev does, but if you don't then I don't think plates are the right solution to the S/N problem.

All I ask is for all players to be advised that you may encounter some differences in the feel of plate pitch antennas, and for new players to be careful what antenna system you choose to learn on.  The time investment that you make in learning to play any musical instrument makes your initial choices extremely important.  Sometimes the best way to decide how or what to play is to look at the players that you would like to emulate and see what they do and what equipment they use. 

BTW - the volume antenna is much less of transition issue whether you choose a plate or loop.