This module is a variation on the Serge Quad Voltage Controlled Amplifier (QCA) module, and can be configured to work for several other Serge designs such as the Universal Equal-Power Audio Processor (UPAP).
From the 1982 Serge catalog:
The QUAD VOLTAGE CONTROLLED AMPLIFIER (QCA) employs four high quality VCA's. Each VCA has one input suitable for DC control voltages to control the overall amplitude of the audio input signal. Envelope generators or sequencers are normally patched to this input. A second control voltage input is ideal for amplitude modulating signals. This input has less dynamic range than the other input and normally oscillators or other control voltages are patched to this input for simultaneous modulation and gating functions. A mixed output of all four VCA's is also included, so that the QCA can be used as a four-in/one-out voltage controlled mixer with independent level control for each input. A unity gain input is used to bus other QCA's together to form mixers of eight, twelve or more input channels.In addition to this, there are extra mixer have been added to the design, giving alternate mixed combinations which are useful in some of the other configurations.
A little on how it works:
The CGS101 QCA uses four CGS108 Serge Gain Cells as it's voltage controlled elements. Refer to the CGS108 page for construction details. The boards are built exactly as per that page. They 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.
On the CGS101 VER1.0 PCB there are some corrections required.
Heat shrink tube was wrapped around the transistors to assist with temperature stability.
There should be no setup required, other than to set the trimmers on the CGS108 PCBs as described on that page.
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.
Article, art & design copyright 2013 by Ken Stone