Silicon Chip Opto-Theremin

The September issue of Silicon Chip magazine contains part 1 of a 2 part series on construction of an "Opto-Theremin".

"This completely new design uses an optical proximity sensor to provide a more effective volume control plate which adds the possibility of rapid tremolo, while vibrato can be applied in the normal way via the vertical pitch antenna".

Main Features:

• External pitch adjustment control
• Linear pitch change with hand movement over four octaves
• Linear volume control with hand movement
• Adjustable hand volume range
• Voicing adjustment (internal)
• Integral loudspeaker with volume control
• Minimal pitch drift during warm-up
• No volume control drift during warm-up
• 9V AC or 12V DC operation @ 250mA (from plug-pack or battery)
• Line output level: 250mV RMS
• Frequency range: <40Hz to > 5Khz

GTC "This completely new design uses an optical proximity sensor to provide a more effective volume control plate which adds the possibility of rapid tremolo, while vibrato can be applied in the normal way via the vertical pitch antenna".

Hey that sounds exactly like what I read on how to increase volume attack earlier in the "staccato pedal thread" before it got all complicated with try at your own risk warnings. That original guy showed his results with audio sound samples to allow his method to be experienced. Maybe they are working together?

T

Edit: I just found it again, second post down has a link to his method, I have seen his pages before and this gentleman has many interesting ideas.

""This completely new design uses an optical proximity sensor to provide a more effective volume control plate which adds the possibility of rapid tremolo, while vibrato can be applied in the normal way via the vertical pitch antenna"."

LOL ;-)

"completely new design" Yeah, new in the 1930's perhaps!

"a more effective volume control plate which adds the possibility of rapid tremolo" - Again, stuck in the 1930's when some VCA's were slow.. A modern capacitive volume plate has no problem with "rapid tremolo"

Why hasn't optical been used on ANY pro (or good) theremin? Simple - because its inferior to capacitive sensing! - The best volume detection employs phase comparison, and if SC really was interested in "more effective volume control" they should have developed this.. But they chose the easy optical route - Not quite as crap as some designs I have seen which use ambient or directed light and are subject to optical interferers - but certainly nothing to compete with capacitive sensing and nothing "new".

Fred.

I have moved my reply to Troll to Here

Some sample pages of the September issue can be viewed here. Opto-Theremin article starts on page 20:

http://www.siliconchip.com.au/Issue/2014/September

http://www.siliconchip.com.au/Issue/2014/September

I got the page to load but did not find any accessible sound bytes. I find it fascinating they go outside the box in design and don't try and dissect everyone else for their ideas.

I guess I need to log into their site?

T

One look at the picture of this toy theremin is enough to completely write it off and discard if as yet another load of rubbish designed by someone with no comprehension of what a theremin actually is, or how it is actually played by anyone who wants to use it musically.

And the claims of newness are false - there are several "theremins" with optical sensors on the market at this time, and none of these are of any use musically other than for sound effects.

Silicon Chip have made a load of theremins - they all share a common incomprehensible flaw in their "out of box" or "as published" state - the distance between pitch and volume antennas is too close.. too close by a long way! Interaction between the volume and pitch hands on their designs makes all their instruments unplayable unless these antennas are moved a lot further apart. This "theremin" is even worse than prior ones in this regard, as the metal front panel will act to increase the capacitive coupling from the volume hand to the pitch hand, with the vertical volume movement directly influencing the pitch field even more than the normal abysmal coupling one gets by having volume and pitch hands so close.

Blue leds for "bling" ;-) Yeah ..

Just another toy with inflated claims regarding "newness" and usability.

Advice to any theremin wanna-be or constructor? Yeah - IGNORE THIS TOY! - Its not even worth the time it takes to read the article, let alone the cost of buying this article!

But hey - wadda I know? - its got (or claims to have) "Bling" - And perhaps that's the most important thing a modern "theremin" needs!

;-)

Fred.

They talk about volume side temperature drift like it's something that plagues Theremins.  And just as they start addressing pitch linearity the article preview ends.  Without being able to see the schematic it's hard to tell how original the design is.  Most likely nothing to see here.

I know the whole "is it really a Theremin?" subject is fraught with authority issues, and I could end up eating my words, but this strikes me as a pitch only Theremin with a gimmicky volume thing tacked on.

"I know the whole "is it really a Theremin?" subject is fraught with authority issues, and I could end up eating my words, but this strikes me as a pitch only Theremin with a gimmicky volume thing tacked on." - Dewster

The core Silicon Chip / EPE / Jaycar theremin design hasn't had a substantial change to its oscillators in years - There have been various "remarkable" improvements and "new revolutionary additions" to it which have come and gone, be these adding a completely useless series antenna inductor to the pitch VFO (which wasn't changed to alter its behavior and exploit any benefit other than increased antenna voltage). or a "Midi" theremin which was based (if I remember correctly) on the same front end.

So I suspect its the basic S/C front end with "gimmicky volume thing tacked on".

But whatever it is, it most likely aint worth thinking about !

The core S/C kit is quite a nice cheap starting point for entry into the world of theremin construction - Throw away the box and speaker, modify it a bit, put it in a correctly sized box, change the antennas, and one has a simple theremin the average constructor can put together.. Use the power amp as a waveshape distorter (As Enkelaar did) and some thereminists have even declared it the closest to the RCA sound they have heard! ;-)

But until they better the core (and the EPE-2008 did at least better the VCA) all these other gimmicks are just a waste of everyones time. The designer really should look at Thierry's post here on how the parallel tank with series resonator works, and look at why volume and pitch sensors need to be further apart - because he really doesn't understand enough about theremins to be publishing construction articles on them! - The only usable versions of his designs are those which have been modified by people who do know what they are doing!

Fred.