Posted on Feb 6, 2014

This describes my original design dual channel quantizer inspired by Chris List`s ARP Style CV Quantizer design. My new implementation is an intelligent design that exploits the programmability of a Microchip PIC16F84. It will quantize voltages in 1/12 volt (semitone) or 1 volt (octave) steps from 10V to 10V. Quantization time is about 2ms per

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channel. Octave switches allow the user to select between semitone or octave quantization. On a per channel basis, this design uses a digital-to-analog converter (DAC), a comparator, and a sample/hold to continuously quantize an analog signal. A suitably programmed PIC drives the quantization process. The addition of a second comparator and sample/hold is all that is needed to get a second channel. Even more channels can be added at the expense of PIC pins and conversion interval per channel. The DAC is multiplexed among all channels. The design was built to the MOTM format using the MOTM-000-A1 DIY breadboard with power cable and mounting bracket from Synthesis Technology. I also purchased the MOTM-1UB blank 1U panel for the front panel. Other parts were obtained from my own personal stock, Mouser, and Digikey. See the schematic and source code to follow the design discussion. The circuit engine is a Microchip PIC16F84 microcontroller (U1) clocked at 10MHz and an MP7542 12 bit DAC (U2). Op amp U3B converts the current output of the DAC to a voltage output. Op amp U3A allows the trimming of the zero voltage point and control voltage scale. The components used around U3A were selected to achieve standard 1V/octave CV scaling. Channel 1 sample/hold is built around U4A, C18, and U5A. Channel 2 sample/hold is built around U4B, C19, and U5B. Resistor R5 provides some slew limiting to keep down noise. Channel 1 comparator is U8....

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