On 29-Dec-10 19:41, IVP wrote:
>> That is basically Bill Hewlett's design for gain control of his
>> oscillator.
> Light bulbs and CdS cells used to be common as voltage/resistance
> controls in instrument effects pedals such as tremoloes, phase shifters,
> the Univibe, panning circuits etc. Then VCA ICs like the MFC0640
> and MC3340 came along


     There are these opto isolated and controlled resistive attenuator:

     http://www.silonex.com/audiohm/levelcontrol.html

     Mark Jordan

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