Completed: D-Lev Digital Theremin Prototype PIII

"How did you select top panel tilt angle?" -Buggins

I set the panel angle to stay within the recommended LCD viewing angle for both standing and sitting positions.

"What angle you are using in your design?"

The angle was initially planned to be about 20 degrees from horizontal, but in the end the internal dimensions needed to fit everything inside drove this to the uneven number of 21.7 degrees. You would want to check your own display before deciding on the panel angle.

"Is screen visibility good enough?"

Visibility and contrast is excellent from both positions.  Even the white on black display which is more sensitive to viewing angle looks great from both positions.  The D-Lev LCD does have a pot for optimizing display contrast, which I did adjust to give equal contrast at the two playing positions.

"What is spacing between encoders? Is it feasible?"

The vertical spacing is 25.4mm. This spacing is knob-dependant, and you can have tighter spacing with smaller knobs (look at how they do it on compact Euro-rack modules).  Small-diameter and easy-grip knurled or rubberized knobs like those used on audio mixers work, but you do end up with the pointers which are unnecessary and kind of annoying for continuous-rotation encoders.

but you do end up with the pointers which are unnecessary and kind of annoying for continuous-rotation encoders
-- pitts8rh

It looks like for encoders we need knows w/o pointers, and for pots - with pointers, and they should be in the same style. Is it ever possible to buy such knobs somewhere?

Printed knobs could be a solution. I don't have 3d printer. Is there any service for 3d printing, similar to one for PCB manufacturing?

"Printed knobs could be a solution. I don't have 3d printer. Is there any service for 3d printing, similar to one for PCB manufacturing?" - Buggins

There are lots of them here in the US, so I would guess you have some as well, but it doesn't take too many prints before you would have paid for a printer.  I think Eric got his Creality Ender 3 for around $200 USD. 

Another option that makes a very functional encoder knob is to find some silicone vacuum caps like these cut them to the right length:

https://www.ebay.com/itm/254292999101

They aren't fancy but functionally I think they're perfect.  The soft silicone gives a good grip and they are only about 8mm in diameter.

Another option that makes a very functional encoder knob is to find some silicone vacuum caps like these cut them to the right length:
-- pitts8rh

Thank you! Never heard about such option

Tried to search aliexpress for "silicone vacuum caps" - found ones with flat top (looks better for me), and of different colors.

Cons:
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

Does someone know encoders with soft pressing push buttons?
Bourns PEC12R I've tried are really hard to press. But I believe there should be some softer devices available on market.

dewster - “ . . . 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!”

I don’t know how I missed your post but I’ve been busy with other music stuff over the past couple of weeks - two performances with different orchestras in NYC and I just got back a couple of days playing chamber music in PA with a couple of friends / both of whom were also recently vaccinated. FYI, I’m in the Pfizer trial and have been vaccinated since September. 

I would be delighted to see a demo of the D-Lev!!! I don’t think that Boonton, NJ - I’m in Basking Ridge, NJ but I’ve only been here for about six years. I’m a transplant from southern California so anything, anywhere in NJ is close to me by So Cal traffic standards  

"I would be delighted to see a demo of the D-Lev!!!"  - ContraDude

You should probably get the manual first so you'll have a better idea of what it is you'll be demoing.  Roger and I are currently working on it, but most of the pertinent info is in there.

Other than my super ugly (though entirely playable) demo model, I don't have anything pretty to show and tell.

Contact me via email, which is in my user bio: http://www.thereminworld.com/user/dewster and we'll arrange something.

This post intended for the Theremin General forum seems to have gone into moderation purgatory. Twice.  So I'll try it here since I bought it to go with this project.

An interesting portable speaker/amplifier for theremin or guitar

I had the good fortune to pick of of these little battery-powered (or optional AC-adapter powered) monitors on eBay a little while ago, and it's quickly becoming a favorite portable theremin amp for personal monitoring:

It's called the Roland Mobile AC, and it's a dense and rugged little unit.

It's not going to overwhelm you with bass, but it has dual speakers, five inputs (two 1/4" for guitar and mic, stereo RCA, and one stereo audio 1/8") with individual level controls for audio, mic, and guitar. The other end has the power switch, adapter jack, and a stereo headphone output. And it has a variable reverb and switchable chorus and wide effects built in.  The clarity and presence with a theremin is great for monitoring, and I find it really handy to have something that is known to be ground-isolated when testing theremin noise issues.

It uses AA batteries, supposedly good for 15 hours.

I had one of these in a shopping cart for about a week while I second-guessed it, but just before I pushed the Buy button one popped up on eBay for $65 with free shipping (about half the new price).  It was a new demo that had been set aside because it was supposedly intermittent (a potential easy fix), but if it ever had a problem it hasn't shown up yet.

Did I save any money in the end? Not really.  I liked it so much that I bought the second one that had been sitting in my cart the whole time just to keep on my bench.  Lately I've been using it as a pitch preview monitor too.  I haven't tried it with an acoustic guitar but it is often suggested for use as a lightweight busking amp.  It even has a threaded insert on the bottom to mount it up on a mic stand.

Entirely decent for the price, IMO.

P.S.  I should add that you'll have to provide some form of ground return for your theremin since this is entirely isolated.

"And it has a variable reverb and switchable chorus and wide effects built in."  - pitts8rh

Sweet!  What's the reverb like?  And the chorus?

The reverb is actually quite good IMO for theremin use, with a delay that's probably on the order of what you would associate with a "Medium Hall" reverb effect.  It's not a Lexicon, but it has some clarity that I wouldn't have expected.  The chorus function is there but it's not something I use with theremin or guitar.  The clarity of the amp in general really caught me off guard (in a good way) when I tried it with some of the brighter D-Lev voices.  I didn't mention it also has a single tone control.  

Actually the Wide button is really effective with the theremin and makes the little box sound about 2-3 times as long as it is (which is about 11").  I always have it in this mode.  A portable amp with all of these different inputs that are separately mixable is handy to have around for a lot of uses.