Oscillating

Continuing with my story from yesterday's post on the birth of PS Audio's original name, Infinitizer, the tale continues in Germany. Less than 6 months after learning from Giorgio Moroder's engineer how a Moog worked I figured out the design of a voltage controlled oscillator and built 6 of them in a project box with 1/4" input and output jacks. This was in Munich, late 1972 and my girlfriend at the time, Terri (the future Mrs. McGowan), painted its front with psychedelic rainbows. I wish I had a picture of that box but after 43 years there's not much hope of that. An oscillator is an electronic circuit that generates a tone. What is a tone? Click here If you clicked, what you heard was a single 440Hz tone, the same as A on a piano. Of course, that tone doesn't sound like a piano, but it's the same note (or frequency). Trust me. If you take your new understanding of an oscillator's function a step further, we come to learn some oscillators are variable; their tone's frequency is not fixed. Typical of that day oscillators had knobs to vary frequency; turning them would make the tone go higher or lower in pitch. New to me was the idea of an oscillator (tone generator) that varied its pitch not by turning a knob, but by varying a voltage. This meant instead of a knob to adjust frequency a voltage could do the same: higher voltages created higher frequencies. Musical synthesizers used these voltage controlled oscillators to great advantage. By building a piano-like keyboard that produced a different voltage per key, which then set the oscillator's frequency, each press of the ivory produces a different note. Because Octaves on a musical scale are frequencies doubled, it was a simple matter to output twice the voltage level for each octave, and evenly divide the inner keys. If you listen to the 440Hz note in the example I supplied you might wonder how that simple tone could eventually form approximations of different instruments. The answer lies in the type of output from the oscillator: sine wave, square wave, triangle wave, sawtooth wave. Each waveform sounds dramatically different. If you'd like to understand this, click here for a demonstration. Start with the sine wave demo. Next, try the square wave demo. Note the difference in sound between the two. That difference is called harmonics. Square waves have lots of harmonics, sine waves have none. Try it, and tomorrow I'll explain why that mattered when it came to making synthesizers have voices.