Analog servomotors

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JohnRoberts

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Lots of moving faders use simple motors with a DC voltage on the sense winding.

I did a bunch or work with digital pots, for a microprocessor controlled analog, automatic mixer. I designed the prototype to accept either DBX VCAs, or DPOTs. I fired up the DPOTs first and they worked so well I never bothered to fire up the VCAs. In theory DPOTs can have zipper distortion, but I found in use they sounded adequately transparent (on speech). I even designed in zero crossing synchronization so the gain changes could be forced to occur only at zero crossing (to eliminate clicks). I didn't need to implement that either.

FWIW the Automatic mixer application is dealing with speech and modest gentle gain changes. This SKU never got evaluated by critical customers in the marketplace so my opinions are purely subjective.

Sadly the company I designed this for (still around just barely) got spanked by low cost digital mixing platforms. The market for a digitally controlled analog (automatic) mixer would be vanishingly small.

In hindsight I could have made my microprocessor controlled automatic mixer even better by adding some relatively inexpensive A/D convertors but that opens another can of worms...

JR
 

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