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Modulation system

  • US 3,999,149 A
  • Filed: 06/20/1975
  • Issued: 12/21/1976
  • Est. Priority Date: 06/20/1975
  • Status: Expired due to Term
First Claim
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1. A modulating system for an electronic musical instrument comprising:

  • a first transistor and a second transistor forming a pair of transistors, said transistors having a base, emitter, and collector, said first and second transistors having their emitters connected together;

    a source of audio current signals connected to the emitters of said first and second transistors;

    a first resistor connecting the emitters of said first and second transistors to ground;

    a first source of essentially fixed DC bias voltage connected to the base of said first transistor;

    a second source of DC bias voltage connected to the collectors of said first and second transistors;

    a source of control voltage connected to the base of said second transistor, said control voltage having an AC modulating voltage component and a DC modulating voltage component for modulating the audio current signals; and

    a current summing amplifier having an input and an output; and

    collector means for connecting the collectors of said first and said second transistors to the input of said current summing amplifier so that said control voltage modulates the percentage of said audio current signals reaching the output of said current summing amplifier over a wide dynamic range, and so that the percentage of said audio current signal reaching the output of said current summing amplifier is further modulated by said AC modulating voltage component causing the percentage of audio current signal modulated by said AC modulating voltage component to remain essentially constant over said wide dynamic range, and the amount of AC modulating voltage reaching the output of said summing amplifier is reduced by cancellation.

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