CGS TPS Touch Activated Programmer Sequencer

CGS

Sequencer

Touch Activated Programmer Sequencer

This is info for the keyboard (see website), but I suspect, given the name, that this incarnation does a bit more. With "programmer" features included as well.

Serge Touch Responsive Keyboard
for music synthesizers.

Derived from the Synapse, January/February 1977 magazine article:

Note that by itself, this project can only provide Gate signals and voltages responding to pressure being applied to the pads. There are no musically pitched voltages generated. That must be handled by external circuitry such as the Programmer/Sequencer.

This keyboard may be made with as many keys as you like, though the value of RPD (15k) may have to be made smaller as more keys are added. Each key provides for touch proportional voltage and pulse outputs. The pulse output stays high for however long the key is touched. In the schematic, each stage's touch voltages are combined through a diode network resulting in an output dominated by whichever key is touched hardest. This function is optional, but is useful if you wish to use the keyboard (in conjunction with Programmers) to play melodies with touch control of their dynamics.

How to use this module:

The keyboard may be built and installed to fit any flat surface, for example, the body of an electric guitar. Make sure that all components are mounted in close quarters with the touch keys. Wiring should be kept tight. Note that the pattern surrounding each key should be grounded. Connecting your touch responsive keyboard with a Programmer will result in an exceptionally powerful unit, able to access as many presets as you want at a touch. This means too, that your keyboard will be able to perform non-tempered scales since each of the keys can be preset to a different tuning.

A little on how it works:

On the CGS86D Driver PCB: The transistors make up an emitter coupled astable oscillator with a somewhat distorted square wave output of about 100kHz.

On the CGS86 Detector PCB: The first amplifier for each of the two stages shown a full wave rectifier and filter whose output goes positive as more of the 100 kHz is shunted to ground by touching a key. The second amplifier provides the pulse output.

The circuit may be operated with +/-12 or +/-15 volt supplies, although the output voltages will be higher on the higher supply voltage.

TKB:
https://www.elby-designs.com/webtek/cgs/serge/cgs86/cgs86_trk.html

Programmer/Sequencer

The Programmer/Sequencer is a Serge inpired multi-stage sequencer. Unlike most sequencers, this one makes no use of binary counters. Rather, it uses a set of individual stages, each one directly accessible. As such it could be considered to allow "random access".

This module replicates the programmer, but with one major exception - left and right inputs allow it to be sequenced without connection to an external gate source. Any stage can be activated at any time by a direct pulse or button press. Left/right pulses will then step it from that stage. To limit the number of steps in the sequence, the pulse (gate) output of a stage is simply routed to the external pulse input for the first stage of the sequence. Note that the first stage used in a sequence need not be the first stage on the panel. For example it would be possible to have the first few stages used as an "introduction", with the sequence automatically looping to a stage in the middle of the panel once the sequence's first run was completed. There is also no theoretical limit to the number of stages that can be used. The maximum number of stages is, of course, chosen prior to building.

In addition to the individual 'stage' outputs, two additional outputs are provided:-