Xor Modulation Mutliplexer
The experiment uses a series of NAND gates as switches to input into a network of XORs. The LOGIC diagram for the NAND is
X Y out
———
0 0 1
0 1 1
1 0 1
1 1 0
This can be used as a switch of sorts because if one of the inputs is low, the value of other is pretty much inconsequential and the output is high. Once that is passed on to the XOR, it makes the XOR effectively an inverter . This really has no effect on the final sound of the output.
So you can take a group of squarewave signals and selectively XOR modulate them by having the input of the selection NAND as high.
By the way “XOR Modulation Multiplexer” is not a real name, its just something I kinda made up. This little sub circuit probably has a real name. Email me if you find it.
Putting this into good use, I reused the PWM noisemaker circuit from a previous folly and put it to work.
The plan was to use all 6 inverter circuits from a 40106. Three for the PWM flasher circuit. Two as audio squarewave oscillators. These would have an LDR driven by the LEDs from the flasher circuit. Finally, the last one would be a slow oscillator driving a counter. The counter would toggle the inputs of the NANDS thus XORing the two signals and…well…for good measure I put in the yelp from the PWM circuit.
The results were…well…umm…not steller. Interesting to see how it turned out, but I wouldnt commit it to a breadboard. The LDRs were made with radio shack light sensitive resistors, LEDs I got from a string of Christmas lights and a low budget glue gun. Needless to say, individual results may vary.
For the first sample, the counter regulates the input of the XORs. There are three pots. The first controls the speed of the PWM fader. The second the frequency of the PWM yelp and the third the clock for the counter.
For the second sample, I removed the clock. Seemed pointless. Sample was of me toggling the inputs of the NANDS from high to low. Some knob twisting too.
