Rob the Fiddler

This experiment centers around the 4089 chip. It is billed as a frequency multiplier but really it multiplies by multiples of n/16. Its really a divider.

The chip has four inputs (A,B,C,D) that determine how to divide the clock and output the pulses.

The output is as follows.

As you can see, a divide by 5 (or multiply by 5/16) is not symmetric at all so this chip is useless for finding things like a real 5th or a 3rd below the clock.

Its a strange chip that is a hold back from the days when it made more sense to hardwire a math problem than use a microprocessor.

This device may be used in conjunction with an up/down counter and control logic used to perform arithmetic operations (adds, subtract, divide, raise to a power), solve algebraic and differential equations, generate natural logarithms and trigometric functions, A/D and D/A converters.

Regardless, it is the basis of this experiment.

I envisioned a circuit that cycled through the divider states with a counter. I had hoped that the cycle would be interesting….but it didn’t live up to expectations.

The circuit I used was as follows:

Here is a sample of what it sounds like with an audio frequency and a low frequency going through the counter so that I can clock though all 16 states of the frequency divider.  You are hearing it go through 1/16 to 15/16 in steps of 1/16.  Still, since the division is not equal, it sounds mostly like we are adding/subtracting frequencies rather than changing pitch. Thats to be expected.

Yah…meh.

To be honest, I didn’t see a lot of potential for the counter in a modular or lunetta synth. I found that clocking through a few items and using the “clear” pin (which basically lets the clock through undivided) yields a much more interesting:

I would suggest that a modular/lunetta that used this chip be as bare bones as possible. Something like this.