EPE 2011 anyone?

Posted: 10/12/2011 1:41:10 PM

From: Buenos Aires, Argentina

Joined: 9/14/2008

A friend showed me a new version of the EPE theremin, pubished in Everyday Practical Electronics, March 2011. It is supposed to be an upgrade but:
1) This new version does not have the linearizing coil. Unless some magic happens, I donĀ“t understand why this is not worst than before.
2) The volume antenna is a plate (uhg)

Anyone attempted this version?
Posted: 10/13/2011 10:13:56 AM

From: Colmar, France

Joined: 12/31/2007

The linearization coil in one of the previous releases was quite useless. Using a linearization coil in a pitch circuit requires a completely different oscillator design since the additional inductance does not only interact with the antenna's capacitance but also with the capacitor in the oscillator's tank circuit.
That means that adding a linearization coil to an oscillator which has initially been designed to work without one will not bring the desired effect. So letting the coil away in the EPE design doesn't make it worse.

The volume "sensor" has always been a plate in this design since 2006. While the volume oscillator and discriminator stages in this circuit are not too bad, the volume control voltage processing is. Thus it doesn't matter which kind of antenna you use - you'll always only get an on/off control without further modifications of the circuit.

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