The motional inductance (Lm) and motional capacitance (Cm) of radio frequency crystals are of importance when designing crystal filters for narrowing bandwidth of a device (usually a radio).
I soldered a circuit together and used a test setup invented by a HAM (Hobby Amateur Radio) guy. The math looked scary but you just plunk in your numbers.
You test 50 or so crystals and then group the 10 most similar ones and use them.
Cs = size of the capacitor in the circuit.
Co = measure the capacitance of the crystal with a meter.
^f = the delta (change) between measuring the crystal with and without the capacitor switched on in the circuit. Subtract one frequency from the other.
F = the first capacitor off in the circuit measurement.
Capacitance of the crystal by itself:
Little circuit board kit I soldered up (not the capacitor on/off switch to the left):
Frequencies with/without the capacitor turned on:
The motional parameters of that radio frequency crystal (I was off by some decimal places, lol):
Guitar Distortion Fuzz Overdrive Pedal with 50 diodes!
Ordinary guitar distortion pedals usually have 0, 1 or 2 diodes. Some have 3. I've started making one with 50 diodes attached to 5 knobs. Each knob will have 10 diodes + 1 off/bypass setting.
They are 11 position, 1 pole, 1 deck rotary switches.
Knobs 1, 2 and 3 will have identical sets of 10 different diodes.
Knobs 4 and 5 will have identical sets of 10 different diodes that weren't of the type used before.
That yields 50 diodes--that are 20 different types.
This allows for:
Matched pairs on 1 and 2.
Matched pairs with asymmetrical stacking on 1, 2 and 3. 1 diode on one side, and 2 diodes on the other side.
Matched pairs on 4 and 5. Asymmetrical stacking with non-matching on 1, 2 and 4 or 5.
Smoothing using 4 and or 5 added to 1 and 2 and/or 3.
Here's the diodes wired up. Knobs 1 and 4 have the diodes going one way, 2, 3 and 5 have them going the other way. Diodes need to be opposing in the circuit so they clip the top and bottom of the signal--this is what creates distortion/overdrive/fuzz.
Opposing diodes:
Temporary schematic:
I will be adding a tone knob section (bass/treble) and possibly a selector switch which will short the knobs (diodes) directly to the ground wire which will yield a harder clipping to the voltage through the diodes--more a heavy metal tone vs blues and rock.
Also, going with a 9 pin footswitch instead of 6 pin: that will make wiring easier. In the schematic I'm not liking the current setup for the footswitch (possibly should swap to top wires on right side around).
My greatest issue with circuits: potentiometers (aka volume knobs). Sometimes they are used as voltage dividers/potentiometers--but sometimes as variable trimmer resistors (2 wires vs 3 wires). Here they're being used "properly" with 3 wires.
