## Block - Turing Machine 1.1

### Random Looping Sequencer

#### DESCRIPTION

Update 1.1: Added parameter labels (whoops!). Fixed manual click light on Gate button.

Another Block in Michael Hetrick's "Euro Reakt" series!

This is a Block based on Music Thing Modular's excellent Turing Machine (http://musicthing.co.uk/modular/?page_id=21). The Turing Machine is an open-source DIY module that produces random sequences. It uses a shift register to store 8 binary bits, which are converted into an analog voltage.

To get started, plug a Gate (i.e. a clock source) into the GATE input. Plug the OUT output into an oscillator's pitch input.

So, how does it work? The red squares on the right side indicate the state of the 8 internal bits. Bit 1 (at the top) is the least significant bit, meaning it barely affects the sequence at all. Bit 8 (the bottom bit) is the most significant bit, meaning that it has a huge influence on the sequence. The bits in between are in increasing order of significance.

Essentially, whenever a bit is true (indicated by its square being larger), it will increase the amplitude of the output sequence. When all bits are false, the sequence output is simply "0". The sequence output is unipolar, so it goes from a minimum of 0 (all bits false) to 1.0 (all bits true).

Whenever a gate is received, the shift register advances. The state of BIT 1 is passed to BIT 2, BIT 2 is passed to BIT 3 (and so on). Finally, BIT 8 is passed back to BIT 1 via feedback. The PROB knob changes the probability that this bit will flip. THE PROB knob is functionally identical to the Turing Machine's knob: At full-clockwise (100%), the bits will *never flip*, meaning that you have a looping 8-step sequence. At full-counter-clockwise (-100%), the bit will *always flip*, meaning that you have a looping 16-step sequence. At center-detent (0%, or where you see the small white line on the knob), you will have the most random sequence possible.

When positive, WRITE 0 forces BIT 1 to be 0 (False) on the next incoming gate. WRITE 1 forces BIT 1 to be 1 (True) on the next incoming gate.

At the main OUT, there are 256 possible voltages. At the ALT OUT, there are 9. The SCALE knob affects the maximum amplitude of both of these sequences.

All 8 bits have their own G OUT, turning each bit into a gate. This allows you to replicate the functionality of the Turing Machine's PULSES expander. If you run all 8 outputs into a mixer, you can replicate the VOLTAGES expander (I may expand this Block to include this in the future).

Tip: Attach a square wave oscillator to the GATE input to create a crazy digital noise source...

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