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AM1050 Module - ARP Mix Sequencer
Overview This module is based on the Mix Sequencer module from the ARP 2500 synthesizer, the ARP 1050. This is a straight forward analog switch with some rather cool features. The
original was designed back in December 1970 using TTL logic chips and FET transistors to switch the signals off and on. This module pre-dates the arrival of CMOS logic, analog switch chips. LED's and even decent Op Amps. Pearlman was
pushing the limits of 60's analog electronics.
Description
This module has sequential switching for the rapid selection of preset waveforms and signals into a conventional audio mixer format. There are two four-input mixers with electronically gated inputs, an eight-step counter and clock, and associated logic and switching circuitry. Each input has its own attenuator and each output has a master gain control.
The module can be used as an eight input mixer with two adjustable outputs or as two separate four input mixers.
A column of illuminated push buttons indicates which inputs are gated on. The switches are pushed to change the
state of an input, push-on/push-off. A column of "Exclusive-on" push buttons will turn on a particular input while simultaneously turning all the others off.
 Original Circuit The 1050 has a now obsolete TTL logic core of a 74155 dual 2 of 4 decoder
driven by the 4-bit binary counter 7493 chip, and clocked by a internal pulse generator. This logic provides the eight step counting.
A set of 7474 flip-flops provide the manual latching of the analog switches, and four
75451 peripheral driver chips light the lamps (no LED's) and drive the analog switches. The actual analog switches are simple FET's. Additional logic gates provide individual control
of the switches from another ARP 2500 module, via an internal cable.
The audio signals are mixed into the 2 separate audio outputs using four 1339 Op Amps - candidates for improvement!
AM Circuit
The new circuit makes some radical changes from the original:
- CMOS analog switches rather than FET's to turn the audio channels on and off
- Momentary push buttons with internal LED's to latch the channel on or off
- Exclusive channel select by holding the same button down for more than one second
- PIC microcontroller scans the push buttons and replaces the flip-flop latches
- Audio Op Amps upgraded to high quality OP177's
- TTL counters replaced with CMOS versions
The module keeps the following elements of the original design:
- Analog clock pulse generator, to enable voltage control
- 8x1 or 4x2 channels
Panel To be completed.
Build History To be completed.
Specifications To be completed.
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Site Options
Resources
* AM FAQ's 
* Schematics are at the
* AM1050 Project Notes