Doepfer A-196 Phase Locked Loop [Episode 69]

Published on Jul 7, 2018 CatSynth TV

"An explanation and demo of the often misunderstood Doepfer A-196 Phase Locked Loop (PLL) module. We give a brief definition of a PLL, and show how this maps to the different sections of the module. We then launch into a series of demos of the A-196, first with a simple square wave input, then a more complex signal from the Sputnik Dual Oscillator, and finally the Arturia MiniBrute 2 (with the Brute Factor turned up). Throughout, we explore the different phase-comparitor options on the module, including the basic XOR and more complex proprietary circuit.

Scope provided by Mordax DATA module. In all examples, the input signal is red and the A-196 PLL signal is green.

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From Doepfer's website on A-196:
"this is how a pll works: the output of the internal vco (linear cv control, rectangle output) is compared with an external signal (e.g. the rectangle output of a a-110 vco) in the so-called phase comparator (pc). the output of the phase comparator is a digital signal (low/high/tristate) that indicates if the frequency resp. phase difference of the two input signals is negative, zero or positive. the output of the phase comparator is processed by a low pass filter (lpf) to generate a smooth voltage that is used to control the frequency of the internal vco. the 3 units vco, pc and lpf form a feedback loop that works like this: the control voltage (output of the lpf) increases as long as the external frequency is higher than the frequency of the internal vco und stops increasing when both frequencies become identical. the control voltage decreases as long as the external frequency is lower than the frequency of the internal vco und stops decreasing when both frequencies become identical"

For more information on phase locked loops, please check out this tutorial from Electronics Notes: https://www.electronics-notes.com/art....

You can also find a basic description at https://en.wikipedia.org/wiki/Phase-l...

PLL block diagram from Wikipedia Article."