theremin bamttech


Posted on Feb 5, 2014

This page steps through each section of my implementation of BAMTRAT. Many of the component values shown were determined experimentally, to suit my own tastes and preferences. As when building an acoustic instrument, there is a lot of room for experimentation and customisation in electronic instruments generally, and theremins specifically. A note


theremin bamttech
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on capacitors: here`s an opportunity to use ceramic capacitors, especially the NPO variety. While ceramic caps are generally considered less than ideal for hi-fi audio, they`re terrific for RF; they tend to have less capacitance drift with temperature than most plastic types, and also have a vanishingly small "equivalent series inductance" as compared to capacitors wound with foil and film. This simple-yet-effective "Battery Eliminator" provides the required voltages (+80, +3 regulated and -7. 5) to operate BAMTRAT. It uses two transformers salvaged from 6v, 0. 3A "wall-wart" supplies to step the voltage down for the filament and C- supplies, and back up to supply the B+ voltage. The 6v AC output is follwave-rectified by the positive side of bridge D2-5, filtered by C15, and regulated by an adjustable regulator (LM317), providing regulated 3v for the series-parallel connected tube heaters. It`s a Really Good Idea to include six 1N4002 diodes as shown in blue, as protection in case one or more of the tubes are removed from their sockets; this will prevent voltage from ever exceeding about 1. 8 volts. The negative side of the bridge supplies the negative bias voltage for the power amp, filtered by C14. Since there`s very little current drawn from this supply, even the 47 µF shown is an overkill. The stepped-up B voltage is rectified by bridge D6-9, and two-stage filtered by C17, C13 and R10. Since the PA draws the most...




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