{"id":205,"date":"2023-06-14T11:51:02","date_gmt":"2023-06-14T09:51:02","guid":{"rendered":"https:\/\/radix-studio.fr\/blog\/?p=205"},"modified":"2023-06-14T12:05:59","modified_gmt":"2023-06-14T10:05:59","slug":"converting-a-fairchild-661-gate-to-a-663-compressor","status":"publish","type":"post","link":"https:\/\/radix-studio.fr\/blog\/2023\/06\/14\/converting-a-fairchild-661-gate-to-a-663-compressor\/","title":{"rendered":"Converting a Fairchild 661 Gate to a 663 Compressor"},"content":{"rendered":"\n

The Fairchild 661<\/h2>\n\n\n\n

The Fairchild 661 is an optical gate which has nothing to do with the very famous Fairchild 660. <\/p>\n\n\n\n

The 661 a quite simple unit:<\/p>\n\n\n\n

  1. The input signal goes through a teansformer then a transistor based circuit<\/li>
  2. The result is used to light a bulb<\/li>
  3. The signal to be \u00ab\u00a0gated\u00a0\u00bb goes through a \u00ab\u00a0Light Dependant Resistor\u00a0\u00bb (LDR). When the light bulb is bright (ie. a loud level), the resistor value descreases, thus the signal is not attenuated.<\/li><\/ol>\n\n\n\n

    The 661 includes a Threshold and a Release knobs.<\/p>\n\n\n\n

    <\/p>\n\n\n\n

    So what about the Fairchild 663?<\/h2>\n\n\n\n

    The Fairchild 663 compressor, uses basically the same circuit but this time the LDR is connected from the signal to the ground. Thus, when the light is bright (ie. a loud level), the resistor value decreases and more signal goes to the ground.<\/p>\n\n\n\n

    Let’s look at the circuits!<\/h2>\n\n\n\n
    \"\"<\/a>
    Fairchild 661 gate<\/figcaption><\/figure>\n\n\n\n
    \"\"<\/a>
    Fairchild 663 (compressor)<\/figcaption><\/figure>\n\n\n\n

    <\/p>\n\n\n\n

    \"\"<\/figure>\n\n\n\n

    If we compare these two schematics, we can see that:<\/p>\n\n\n\n