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Vintage threads from the first ten years
| previous: Anders Mutron III photocell substitute -- 10/30/2000 5:03 PM |  |
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CAUTION: Heresy ahead
 11/2/2000 3:35 PM |
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Mark Hammer | CAUTION: Heresy ahead Within a wide range of limits (and these would include rise and fall times, in addition to DC resistance), it really doesn't matter what you use. The Mutron, and any similar state-variable filter circuits, depend upon the *parallel* resistance of a fixed resistor and LDR, in addition to a capacitor, for their centre frequency. If you can't get the exact LDR ON/OFF resistance values you seek, you can always just change the parallel (220k) resistor so that the sweep IS what you want. If the combined LDR/R resistance produces an inappropriate range of frequency sweep in conjunction with the caps, than simply tweak the caps, and perhaps consider sticking in a series resistor ahead of the LDR/R combo. One of the things that the Mutron and clones lack is a way to fine-tune the width of sweep. In the 2nd version of the ECF paper that I sent to RG to post (Hope you got it, buddy), I spend a bit of time discussing how to fiddle with the combined LDR/R's and series resistors to vary the width of sweep and initial frequency. Of course, if your mission is to repair someone else's stock Mutron and have it stay "vintage", kindly disregard this posting. |
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| Anders Thanks a lot for the info. I'll try... -- 11/10/2000 1:45 PM Bob Predaina` Mark, |