Moog Theremini!

... The sad thing is that it has "Moog" on it.

Amey,

That is the truly sad thing...

It has "Moog" on it-

But absolutely no Moog in it.

For those who admired Bob Moog, putting crap like the theremini on the market, and putting Bobs revered name on it -

That is an utterly unforgivable offense.

Fred.

I certainly don't go out of my way to avoid the TW home page, but in the course of things I don't often find myself visiting it, though there are many interesting things to be found there and I applaud the effort that goes into maintaining it.  Anyway, I completely missed this letter by Mike Adams, the President of Moog Music Inc.:

http://www.thereminworld.com/Article/15527/moog-music-responds-to-theremini-feedback

I wrote a response but it didn't get posted, and I thought maybe it was due to me entering it on another PC even though I was logged in.  Posted again a few days ago on my home PC but the moderators apparently haven't gotten to it yet.

In lieu of that I'm commenting on the article in this here thread:

"Sometime in the near term expect to see a user installable firmware update that will significantly increase the player experience of the Theremini."  - Mike Adams

Not holding my breath.  You know, I get bug updates, but major functionality updates are an indication the thing was rushed to market, with who knows what in the way of corners cut / things not completely thought through in the HW as well.

"To ensure that frequency latency is not an issue, we heterodyne to a much higher frequency and then down-scale the frequency when outputting our oscillator waveforms. This, of course, is absolutely critical to the performance of the instrument.  The heterodyne circuit is actually a very necessary part of the design of the Theremini. We would never utilize circuitry in a design that didn't provide a necessary function for an instrument not only on principle but it just doesn’t make sense from a manufacturing point of view. The heterodyning of the oscillators allows us to take advantage of higher time resolution and lower noise – both of which are essential to the performance of the instrument.

So, it is the combination of both heterodyning but still keeping the frequency higher than normal audio rates that allows high-resolution frequency sampling but still maintaining very low-latency in the measurements (typically less than 60 usec)."  - Mike Adams

1/60us = 16.7kHz, which is probably the minimum heterodyned frequency (far field).

Anyway, here is my response (which has yet to be posted):

Mike, thank you for taking the time to answer our questions and address our concerns here at TW. 

I'm an EE actively researching Theremin technology and currently own a Theremini.

Using two different techniques I've roughly measured the overall pitch side time constant as somewhere between 0.06 to 0.1 SECONDS, which is a far cry from 60us, so there appears to be some major low pass filtering / averaging going on somewhere in the critical path?

The voltage swing at the antennas is quite low - is this for emissions compliance reasons?

I've opened up the Theremini and don't see evidence of ESD protection for the pitch and volume oscillators - why is that?

Hi Dewster,

I missed this post! (and the letter from Mike Adams)

Has there been any reply to your comments yet?

Fred.

"Has there been any reply to your comments yet?"  - FredM

Unfortunately no.  I PM'ed Jason and he said my reply got stuck in the spam filter, as did one by Mike Adams in the (this?) Theremini thread.  He unflagged them and said that would fix things but I'm still not seeing them.  I'll send Jason another PM.

Jason PMed me and said he didn't see any comments pending.  I just tried posting to that story again but no immediate dice, it tells me my comment is in moderation.  It's probably just a bug in the TW software.

Hi Dewster,

Ok - Im completely lost now (not that unusual ;-)

"he didn't see any comments pending." " I just tried posting to that story again but no immediate dice, it tells me my comment is in moderation."

?

Where are these "comments" or "that story" ?

Is this on some TW forum other than this one?

As for "my comment is in moderation" - I didnt know this happened to TW members! - Didnt even know there was a mechanism to do this!.. Wasn't this suggestion put forward in the "spam war" but rejected because it was too complex? Has it now been implemented?

And while we are on the subject..

Who shot JR ?

;-)

Fred.

"Where are these "comments" or "that story" ?  Is this on some TW forum other than this one?"  - FredM

It was an article on the default home page of TW:

http://www.thereminworld.com/Article/15527/moog-music-responds-to-theremini-feedback

I think the moderation my comments are getting stuck in is for brand new members in order to head off bot spam.  Third time posting evidently wasn't the charm for me, maybe there's some kind of limit to the number of article comments?

I shot JR!

Hi Dewster,

Ok, I managed to post there.. (http://www.thereminworld.com/Article/15527/moog-music-responds-to-theremini-feedback) I copy my post here:

"So, it is the combination of both heterodyning but still keeping the frequency higher than normal audio rates that allows high-resolution frequency sampling but still maintaining very low-latency in the measurements (typically less than 60 usec)."

"In the measurements" could actually mean anything - the important factor is latency between movement (capacitance) change and pitch coming out of the instrument. This latency has been measured at something near 100ms - as in, more than 1000 times slower than the 60us you are quoting, and a latency which is unacceptable for any electronic musical instrument and utterly unplayable for a theremin.

60us would not be noticed by anyone, even 600us wouldn't be noticed - but every thereminist who has tried to play the theremini has noticed the delayed response (latency).

Something is very wrong with your explanation and particularly the 60us you are quoting, sorry!

Congratulations Fred!  So it isn't apparently a comment count thing.  I must have done something to make the spirit of TW mad at me.  (Where are those Theremin Shamans when you need them?)

The 60us thing makes me suspect they are talking far field beat frequency.  1/60us = 16.7kHz which is just above most human hearing, and moving the hand closer would increase the beat frequency.  Personally I'm aiming for >40kHz here to stay above and completely away from the sonic range (though it is dependent on oscillator nominal frequency and oscillator sensitivity, and strongly influences near-field linearity - indeed exactly what I intend to use it for - and too bad too that the Theremini designers clearly don't seem to understand this).

If the above is true (?) then I would add that a 60us beat period doesn't automatically mean anything in terms of the precision of the measurement of it.  What is the frequency of the clock are they using to sample the period?