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LM13700 Amplifier/VCO Circuit

Discussion in 'General Electronics Discussion' started by FredF, May 23, 2015.

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  1. FredF


    Sep 16, 2014
    Hi Everyone,
    Several months ago, Kris and other members had been advising me on a project. It was intended to be a guitar effect with distortion and variable stuttering effect.The original circuit used an lm386 for the amplification/distortion, and an lm555 to achieve the stutter (oscillation?).Reference thread "Translate stripboard layout to schematic diagram". The general concensus was that the 386/555 combo had serious shortcomings. Most notably, timer noise leaking from the 555 into the output. Kris had suggested using the lm13700 dual op-amp to achieve both effects with one component. After Kris' untimely passing, I put the project aside,not feeling able to continue. Now I feel I owe it to Kris to finish it.
    My problem is after pouring over the 13700's data sheet, I find it very confusing, given my non-existent experience with op-amps. I am hoping that someone in this forum might have a schematic for such a circuit that a newbie like myself could understand. Thanks in advance for any help in this regard.
    Again, RIP Kris. You are greatly missed.
    Fred Fajkos
  2. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    The link to your original thread is here. I or someone else will get back with you after reviewing the original thread. The LM3700 takes some getting used to. It is a variable-gain transconductance amplifier. Very versatile, but you need to think "outside the box" to use it effectively. Please scroll down to the bottom of the datasheet and look at some of the applications, especially how to use it as a voltage-controlled oscillator to generate square waves which you then can apply as "modulation" to your guitar audio signal. I suspect this is the application Kris had in mind when he recommended it.
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