Seeking Advice: Playable Digital Schematic

Posted: 2/9/2011 8:50:54 PM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

[i]”How major of an issue will the linearization coils be? is it just a matter of fine-tuning, or are significant alterations likely to be required to make it playable?” –lfb [/i]

I have used the “varnished Chokes” from JW miller / Bourns Available from DigiKey ( and found these to be quite good (not as good as an air coil, but as good as one can get for a ferrite)

These are available in 2.5mH, 5mH, and 10mH (part # M10164-ND, M10165-ND, M10163-ND ). I find that the more inductors one uses in series to get the required inductance, the better it works.. So..

For the pitch antenna, I would buy three off M10163 (10mH), one off M10165 (5mH) and three M10164 (2.5mH) .. with these you can get a total of 30.5, 30.75, 40.0 or 42.5mH, simply by changing the number of M10164’s you fit.. if you fit the lower value coils closest to oscillator circuit you can have "handbag" links which you can use to trim the inductance in 2.5mH steps.. A lot easier than taking turns off, or adding turns to a coil. Fine trimming is, of course, done by adjusting the VFO frequency.

For the volume antenna you need two M10165’s (5mH) and two M10164’s (2.5mH). The price of each is £1.55, so for 11 the total cost is £17.05 (quite a lot of money in my books!) – There are cheaper inductors which work – but they do not work so well. I think these parts may be cheaper in the USA

Please note – I have not used these parts with Etherwave / EM type oscillators – I do not, however, see that this should make any difference.


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