Лев Дмитриевич имел патент (совместно с Л.С.Терменом ), посвященный введению связи между генераторами инструмента. Так достигается выравнивание "виртуального грифа".
Один из немногих, по-моему, производителей не-игрушечных терменвоксов, американская фирма PAiA, выпускающая также аналоговые синтезаторы, тоже предлагает в своих инструментах (продаются в виде "конструктора" для сборки) ввести связь между генераторами:
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My oscillators drift and I have to keep tweaking the tuning ...
The Pitch Trim of your Tmax may be need to be nulled from time to time during a performance, and particularly during the first few minutes of operation, and because of this you may think that the Tmax oscillators are less stable than other designs. This is not actually the case - all LC oscillators will drift slightly over time and the Tmax circuits are no less stable than any others.
In order to keep a difference tone from appearing as the oscillators drift, it is common practice to "couple" them slightly so that below some minimum difference frequency they "lock" to one another. The down-side of this is that coupling sets a floor for the lowest pitch possible. If the coupling is such that the oscillators lock when the difference frequency is less than 130Hz (for example) then the lowest pitch possible will be C3, the C below middle C. In an unmodified state, Tmax is capable of pitches well below C0 - which, in retrospect, may be taking a good thing too far.
The cost of this super low end is that you have to tweak the Pitch Trim control from time to time. If any more than this is required (adjusting the coils, for instance) then something is wrong and the unit is not working up to spec. Maybe the Zener is whacked. Maybe NPO capacitors were not used for C8 and C10, which are the capacitors in the LC Tank circuits.
If you want to add or increase coupling, a simple "gimmick" capacitor between the two oscillators will do the job. For the gimmick, solder a 2-1/2" length of insulated wire to the "top" of R4 (the end that joins with e of Q1) and another to the "top" of R9. Twist these two pieces of wire together. Twisting tighter will produce a little more coupling, looser a little less.
Но, конечно, вопроса о выравнивании грифа они не касались, по-моему. Терменвокс у них - необычный контроллер для их аналоговых синтезаторов.
Схема из-за этого очень сложная. Даже переусложненная.
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