128 Note Sequencer

The one with most unfinished projects when he dies, is the winner ...
An old jungle proverb

Many of our audio/music/synth things have their origin in old electronic magasines like Popular, Radio or Practical Electronics. The Transendent T2000 was published in ETI, and Practical Electronics hosted the rythm box, recently discussed in LMNC's videos. So what else can be dug up from the good old magasines?

Well, I am much into sequencers as they may be a cool way of creating rythms, bass lines or whatever, so why not build yet another?? And Practical Electronics published a pretty wild sequencer back in Nov 1977 - the PE 128 Note Sequencer.

A short presentation of the thingie: The heart of the sequencer is a 128 byte RAM (MCM6810) that is fed by 5-bit binary codes coming from keys that are decoded by a diode matrix. In programming mode, the 5 bits are clocked into the RAM and a counter hooked up to the address lines is incremented. When running the sequencer, an oscillator is clocking the same counter. Also, trig and stop/reset pulses can be programmed into the 3 remaining bits in a data word. The content of the RAM, when replayed is fed to a DAC (ZN425). The design is more than simple with slide and pushbutton switches that actually should be made up by electronic circuitry. The logic parts are for TTL ICs - two 7493 counters, a 74121 one-shot and a 7402 NAND gate. An 741 is buffering the voltage output.

That's my short and very complicated description of how it functions..



Full article from PE