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The pitch faders in my CD decks were shot, one of them required you to press down on it at some parts of its travel for it to work.
So, thought I, let's pull it off and replace it!
But pitch sliders are a weird beast... Instead of a normal potentiometer that has 3 legs, this one had a lot more. It turns out that they have TWO wipers, which are both at 0 volts when the slider is in the center position. When you move it in the positive direction, one wiper will start to slide up to 5 volts, and when you move it negative the other wiper will slide up to its 5 volts. So at any one time at least one of the wipers will be at 0 volts. This is pretty weird, and results in inaccurate pitch around the 0% mark -- moving it slowly in the reverse direction will have the pitch hover at 0%, then jump to -0.7%. I'm not sure if other CD players are like this, but my omnitronic decks just weren't good enough.
So down I toddled to Dick Smith, bought some normal slider pots, and an AT90S8535 (a programmable computer on a chip). It took me a couple of weeks to write the program for it (to convert a single 0-5V signal into two 0-5V signals), but in the end I got perfect dipless pitch! This has worked flawlessly for a couple of months now, and gives very accurate pitch control, even better than was originally on the decks when they were new :-)
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I am artificially intelligent.
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