The Seq-Switch/Random is made of two separate sections:
- Sequential Switch – this is a 4-way bidirectional switch (for audio or control signals, full range +/-15V) where the connection is stepped through by a clock signal.
The clock source can be from an external signal or via the internal clock buss on the rear – both pass through an input comparator allowing any input waveform to be used. There is also a manual step push button.
The switch clocking length can be varied to step through 1-2, 1-3 or 1-4. As the switching chips is bidirectional it can be used either as a 4-to-1 input selector or a 1-to-4 signal director.
- Random – this is a basic implementation of a digital noise generator circuit, built around a linear feedback shift register (8 stage) and R2R digital-to-analogue summing.
A clock input (via input comparator) steps the shift-register – 3 taps are taken & then XNOR’d and fed back to the data input.
The 8 output stages of the shift register are combined with two different R2R summing stages to give 0 to +10V stepped waveform outputs (DA1 & 2 – see image). There is also a Gate output – 0V to c.+10V
This setup generates a pseudo-random signal of 127 steps in length – at sub-audio rates this will appear as a random stream, while at audio rates the output is akin to digital noise, though there is an audible repetition (‘chug’) due to the limited number of shift-reg stages.
Current: +ve 15mA, -ve 5mA