Moog Theremini Theremin

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

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Posted: 8/21/2014 3:04:44 PM
dewster
From: Northern NJ, USA
Joined: 2/17/2012

threads posts

Not to pile on you Touchless, but Theremin seems to have been aware of the downsides if his creations.  He slapped on switchable filters to alter the harmonics, and likely would have been thrilled to add arbitrary waveforms and dynamic filtering.  He also had a crude tuner IIRC. 

Literally anything implemented in older technology can be improved with more modern technology, but engineer-musicians are a vanishingly small lot, and the corporate versions of us aren't given the time to do it right as it wouldn't be profitable in the exceedingly short run on which all modern business seems to operate.  So the buying public gets one older design by Bob (not his best IMHO), a seemingly dashed out Theremini by his replacement(s), assorted hobbyist fare, and the output of talented amateurs / semi-emeritus with a bit of time and/or money on their hands.  There's no telling what you might get from this motley crew, or when you might get it (if at all).

The field of study is surprisingly broad and deep.  I've enjoyed it immensely, but it can be an intellectual quicksand for curious cats.  You have to understand the fundamentals as well as or better than most to find the value in the conventional wisdom (or to challenge it) and then make any headway at all.  Even the simple copying of existing designs is fraught with peril.

Thank god for the free-flow of ideas and info on the web and particularly here at TW, without which I would still be wrestling with the basics (and with the voodoo).  If anything, the biggest challenge to implementing a modern Theremin seems to be the DSP side of things, where the cards are played too close to the chest and the learning curve is quite steep.

Posted: 8/21/2014 4:19:43 PM
Touchless
From: Tucson, AZ USA
Joined: 2/26/2011

threads posts

Not to pile on you Touchless, but Theremin seems to have been aware of the downsides if his creations. - dewster

You can’t pile on me as I am Touchless. The original theremin was perfect by the dictionary definition of the word, it is the birth of electronics. If you have religious upbringing, as I see in your words below, it may have given you a misguided understanding of the meaning of perfect.

Thank god for the free-flow of ideas and info on the web and particularly here at TW, without which I would still be wrestling with the basics (and with the voodoo). - dewster

Really? I don't think your are any closer to the goal today than you were a year ago or even your birth. To try and imitate perfection may be your downfall, in your future I see you tossing your hands up over theremins and walking away. You will ask yourself over and over - What did I miss?  A Voodoo prophecy.

I have no doubt you have amassed more knowledge than Leon Theremin, but you do not have the Vision!

T

Posted: 8/21/2014 9:03:09 PM
dewster
From: Northern NJ, USA
Joined: 2/17/2012

threads posts

"I don't think your are any closer to the goal today than you were a year ago or even your birth."  - Touchless

It probably seems that way if you've been reading this thread for a couple of years.  But there have been a lot of things to investigate and nail down, and Hive - which is a critical component - has consumed at least half of that.  I don't plan on dropping it all tomorrow, but manufacture of anything is a major, major hurdle.

Posted: 8/23/2014 1:32:52 AM
FredM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

threads posts

Dewster,

That troll isnt worth answering! - I know, I take his bait and give explanations, but he comes back with the same snipes and nasty subversive bullshit again and again! his only agenda is to cause unpleasantness and discouragement.. Low life scum! Tell him to stick his crystal balls up his RS!  - Please feel free to use my trash can!

Fred.

Posted: 8/30/2014 7:48:45 PM
dewster
From: Northern NJ, USA
Joined: 2/17/2012

threads posts

I don't know exactly why (other than to understand them better) but I've been playing around with MASH DACs in simulation:

http://www.mediafire.com/download/cpzoa7l088bechf/MASH_DACs_2014-09-01.xls

Unlike other modulators, they're super simple and guaranteed stable regardless of input value and order.  The biggest caveat is they produce 2^N bits of output for order N, so they generally require a small DAC at the output.

Here's a nice treatment of them, in the context of several extremely interesting projects (click around at the top):

http://www.aholme.co.uk/Frac2/Mash.htm

[EDIT] Found some errors in the spreadsheet when simulating in SystemVerilog, so I updated it and the link above. 

There appear to be diminishing returns associated with higher order MASH modulators.  4th order doesn't seem to utilize the output levels at the limits very much.  Also, the output averaged signal is constrained to [0,1] but the output range is 2^N, so more dynamic range at the output is required for higher orders.

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