New Silicon Chip Theremin 2009 edition

As soon as I will have financially recovered from Lippstadt, I'll order a kit and do this verification (among others).

Regarding the 3-terminal regulators ...

You can probably order the various versions somewhere, but the only readily available voltages at local stores are 5V (7805, LM340T-5), 12V (7812, LM340T-12) and 15V (7815, LM340T-15).

The adjustable regulators (LM317T) are also readily available.

Unlike Northern California, Southern California ( especially San Diego County) is very lacking in electronic hobbiests and stores to support them.

Don

I seem to be in a better situation, located in France, near South-Western Germany and North-Western Switzerland within a few miles, I even can choose where to buy and compare prices.

Fred,

Using the MC1496 for gain was probably one of the weak points of the 2000 design. At full output my one's sound is very bland and sine-y, and "theremin-tone" harmonic complexity is only noticeable when the output attenuated somewhat by the volume plate signal. This is consistent with what happens whenever an operational transconductance amplifier is overdriven (lots of synthesiser VCOs use a CA3080 overdriven at the inputs to convert triangle waves into pseudo-sine waves). Max's mods appear to have changed a resistor programming the MC1496's gain so that it doesn't get pushed into this soft clipping region, and the Jaycar deluxe/EPE bypassed this altogether by using the really nice Silonex 32SR3 optocoupler for gain control and relegating the 1496 to function as a simple RF mixer...

Don - Mouser, Allied and Digikey all have the 7809 in stock from multiple manufacturers for less than a buck apiece-why bother with retailers?

I order lots of stuff from Digikey and Mouser ... but you need to have an order of at least $25 in most cases ("to avoid special handling costs"), you have to pay postage, and sometimes you just have to have it right now. ("I want patience and I want it now!") :)

This particularly holds true for power supply parts. You tend to get everything wired up, ready to go ... then work on the power supply for it. Often because you are just so sure that you have that regulator, those rectifiers, that large electrolytic cap in you spare parts bin ... then find you were sadly mistaken.

Don

Justin,
I do not have the schematic for the 2000 - thanks for this information. I have been most impressed with the Silonex 32SR3 - Am almost tempted to buy a big stock (100's) for putting in my Theremins.. But the problem is that I will need to comply with RoHS to get CE certification - so the problem is not just that these parts will become unobtainable, but also that I could find myself with parts I am not allowed to use. I do not much like the LM13700 - and all the other better (for audio) Transconductance amplifiers have been discontinued.. So I have now opted for the THATS 2180 VCA's.. They are expensive and a bit awkward to drive, but sound superb and have the advantage of exponential (log) gain control.

Don.. The LM317 really does solve the majority of small regulator requirements. I also use the TCA0372 (http://www.onsemi.com/PowerSolutions/product.do?id=TCA0372) (dual power op-amp) quite often to produce my own simple custom +Ve or -Ve linear regulators.. In its simplest form this can be configured as a voltage follower buffering a stable reference.

ooops.. Looks like I have used the last slot in this topic.. As this possibly the most active topic here at the moment, I will start a follow-on thread here:
Topic: SC Theremin 2009 - Continued.. (http://www.thereminworld.com/forum.asp?F=3&T=3886&cmd=p&p=1)

Hi,

I agree with thierry. opto-coupler are hard to find and you cannot easily find a replacement for this. It has different specifications that is not close enough to become a substitute for opto-couplers and why did they remove the 10mH coil was remove? It will have a different effect on the circuit and problem may occur when.

 

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