Coefficients/Potentiometers

Coefficients are the quantitative parameters of analog computations. The Analog Thing features eight coefficient potentiometers, allowing the use of up to eight coefficients in an analog program on a single THAT. Using the potentiometers, each coefficient can be set to any value between 0 and 1. An input to a coefficient potentiometer is multiplied by the value the coefficient potentiometer is set, such that their output is given by output = coefficient * input, with the coefficient being a value between 0 and 1 as said before.

For example a variable A is patched into a potentiometer set to 0.123. The output of the potentiometer would be A*0.123, with the same sign as A. No sign reversal is possible with "normal" potentiometer, though tricks have been developed to allow such a thing.

Several sections of the THAT user interface relate to the use of coefficient potentiometers, as shown in Figure 1:

• The COEFFICIENTS section. This is the area labelled COEFF on your THAT. It contains the input and output sockets for the coefficient potentiometers.
• The COEFFICIENT POTENTIOMETERS section. It contains the eight rotary knobs by which coefficients can be set.
• The MODE SELECTOR.
• The COEFFICIENT SELECTOR. It is used to select the coefficient value to display on the PANEL METER when the MODE SELECTOR is in the COEFF position.
• The PANEL METER.

To familiarize yourself with the use of coefficient potentiometers, follow these steps:

1. Set the MODE SELECTOR to position COEFF and set the COEFFICIENT SELECTOR to position 1. This connects the output of potentiometer COEFF 1 to the PANEL METER.
2. Use a patch cable to connect one of the +1 sockets in the STABILIZED ±1 section to the input (circle) associated with potentiometer COEFF 1 in the COEFFICIENTS section (i.e., the uppermost circled socket in the section labelled COEFF on your THAT).
3. Change the position of the COEFF 1 knob in the COEFFICIENT POTENTIOMETERS section and observe the value displayed on the PANEL METER. The displayed value is available at the output (triangle) associated with potentiometer COEFF 1 in the COEFFICIENT section.
4. Remove the patch cable plug from the +1 socket in the STABILIZED ±1 section and plug it into one of the -1 sockets in in the STABILIZED ±1.
5. Again, change the position of the COEFF 1 knob in the potentiometer section and observe the value displayed on the PANEL METER.
6. Set the COEFFICIENT SELECTOR to any one of the other potentiometers (say, 4).
7. Use a patch cable to connect either of the -1 sockets in the STABILIZED ±1 with the input (circle) associated with the with the coefficient potentiometer you have chosen using the COEFFICIENT SELECTOR (say, 4).
8. Change the position of the coefficient potentiometer knob associated with the coefficient you have chosen using the COEFFICIENT SELECTOR (say, 4) and again observe the value displayed on the PANEL METER.

Figure 1: Parts of the THAT user interface that relate to the familiarization steps described above