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This module is a variation of the Serge Dual Channel Stereo Mixer, built using the CGS101 Quad VCA and the CGS102 Equal Power Panner drivers.
Paraphrased from the 1982 Serge catalog:The Dual Channel Stereo Mixer (Dcsm) Is An Alternative Output Vca/Mixer/Panner For Two And Three-Panel Systems. The Dual Channel Stereo Mixer is used for the standard output level control (or enveloping) and for voltage controlled panning. The DCSM has two independent channels for stereo panning. Each channel in the DCSM has two VC inputs, one for amplitude control and one for panning. The panning controls are opposite for the two channels, so that if a single control voltage is used, the output signals will pan in opposite directions. Auxiliary inputs are used to feed other signals into the outputs of the module. Signals applied here will not be affected by knobs or control voltages applied to the module. These are mainly useful for linking other mixers (either manual or voltage controlled) to the output bus. The output is available at a pair of banana Jacks (for routing the signals to other modules within the synthesizer), and at mini-Jacks (for connecting to external amplifiers, tape decks, and other equipment). A little on how it works:
Construction
The CGS101 DCSM uses four CGS108 Serge Gain Cells as it's voltage controlled elements. Refer to the CGS108 page for construction details. It also uses two sets of CGS102 Equal Power Panner boards. Refer to the CGS102 page for construction details. These submodules should be the last things you install on the CGS101 PCB. Before you start assembly, check the board for etching faults. Look for any shorts between tracks, or open circuits due to over etching. Take this opportunity to sand the edges of the board if needed, removing any splinters or rough edges. When you are happy with the printed circuit board, construction can proceed as normal, starting with low profile components such as resistors and diodes first, followed by successively taller components. Take particular care with the orientation of the polarized components, such as ICs, electrolytics, diodes, and transistors. When inserting the ICs in their sockets, if used, take care not to accidentally bend any of the pins under the chip. Also, make sure the notch on the chip is aligned with the notch marked on the PCB overlay. The unit will run on either +/-12 volts or +/-15 volts. The first time you power it up, I would suggest you do so with 22 ohm resistors in series with the positive and negative power rails. This should save the chips if you have made a blunder. While 100k linear pots have been specified, 50k pots will also work in this circuit. On the CGS101 VER1.0 PCB there are some corrections required.
The CGS101 loaded with eight sub modules. There may be some confusion regarding the panel layout and marking of this module. There are two input channels, and two output channels. The input channels are called Channel 1 (on the left) and Channel 2 (on the right). Above them are the two output channels, each with an auxiliary input and a pair of outputs, with the left channel to the left, and the right channel to the right. Take care not to confuse Channel 1 with the Left output channel, or Channel 2 with the Right output channel.
Wiring the DCSM. Note the two wires that run under the PCB. See the modifications diagram above for further details.
Set UpThere should be no setup required, other than to set the trimmers on the CGS108 PCBs as described on that page. Notes:
Parts list This is a guide only. Parts needed will vary with individual constructor's needs. If anyone is interested in buying these boards, please check the PCBs for Sale page to see if I have any in stock. Can't find the parts? See the parts FAQ to see if I've already answered the question. Also see the CGS Synth discussion group.
Article, art & design copyright 2013 by Ken Stone
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