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AM2546 Module - Eµ Programmer
Overview
This module is a clone of the Programmer module in the Eµ Systems Modular Sequencer. It is a very close replica with only minor changes to use modern components and to add some new features. The 2546 is an analog to digital converter that generates a 6-bit binary code (64 states) from a control voltage which can vary from 0 - 5V; this is the same resolution as MIDI, but only a range of 5 octaves (rather than MIDI's 10).
The data is used to program up to fifty 2545 Memory modules with standard 1V/Octave control voltages from either an external voltage such as a keyboard or an internal voltage can be programmed from the front panel potentiometers.
The 8-bit data bus of the 2500 Eµ Modular Sequencer has space for a 2-bit binary code (that makes 4 states) which is generated from the three front panel switches. The Programmer is stepped forward by the rising edge of the GATE
or TRIGGER inputs, and a 10ms positive pulse is generated from the ADVANCE output on the falling edge of a GATE signal. The TRIGGER input is pre-weird to the GATE input, which itself is pre-wired to the Keyboard CV bus along with the
EXTERNAL CV in.
Original Circuit The original design dates back to 1973, and I have cloned the Version 2 schematic and added some new features. The core of the circuit was an analog to digital converter created from a 6-bit R2R DAC,
a LM311 comparator and a 4024 ripple counter. A LM723 is used to provide a stable DAC reference voltage. There is some CMOS control circuitry for the front panel switches.
AM Circuit
The AM circuit is exactly the same except for some upgrades and enhancements:
- Hgh quality ADC based on a modern parallel 12-bit DAC chip
- Emulator 2 style push buttons with latching circuits
- Front panel pots for an internal control voltage
- Revised voltage reference using a 0.6ppm precision voltage reference
The rest of the circuit is a direct clone which has been laid out over 2 separate PCB's.
- A front panel board holds the 2 bit decoder, drivers and buttons.
- A digital board holds the CMOS logic and DAC
There is no trimming.The module needs +5V for the CMOS logic and +15V for the stable 5V reference
supply to the DAC.
Front Panel The panel is a standard AM design, 90mm wide and 4U high, with black lettering. Controls knobs are the standard Eµ Modular design.
Build History
The schematic was transferred into Eagle CAD in the summer of 2005 when I was on holiday in the Peak District (UK). The circuit has been laid out over 2 80x100mm PCB's and a prototype will be tested in the Spring of 2006.
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