The FV-1 Crystal Oscillator


Posted on Feb 5, 2014

The Fv-1 has internal circuitry to support an external crystal, preferably a 32768Hz watch crystal. These crystals are extremely inexpensive and widely available. Frequencies other than 32768Hz are available, but not as cheap and not as plentiful. If the system the FV-1 is integrated into has local clocks available, a logic level clock signal can


The FV-1 Crystal Oscillator
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be directed to pin X1 of the FV-1 through a small resistor, on the order of 10K ohms. Crystal oscillators for these low cost crystals are very different from oscillators designed for megahertz range crystals and resonators. The watch crystal oscillator has very high internal resistances, on the order of 10M ohms. When attempting to observe the crystal signals, the loading of a 10X scope probe can load the crystal terminals to the extent that the oscillator may stop working altogether. Further, leakage across the PCB could cause problems, so be sure to have the product board well cleaned after assembly, if this is not a normal part of your PCB processing. Leakage should only become a problem in the case of very poorly assembled product. NOTE: Some small 32KHz crystals have been found to operate in 3rd overtone mode during startup. It is suggested that the EC-38 style crystal should work well with the FV-1, but smaller crystals have shown problems. In any case, the addition of a 15pF capacitor from the X2 pin to ground will allow all crystal types to function properly. The 32768 clock frequency causes the overall response of the FV-1 to be limited to 15KHz. This may seem insufficient for a quality audio product, but in the case of reverb and most effects, response beyond this range is unnecessary. My own hearing is limited to about 13KHz, and has been since I was in my 20s; neither of my children have been able to hear beyond...




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