CGS Serge equal power panner

CGS102 the CGS Serge equal power panner is a sub-module used in some of Serge's designs, such as stereo mixers and panners. It is essentially a small, purpose made analogue converter that converts and sums control voltages in such a way as when coupled with the exponential response of the CGS102v10 gain cells, you can achieve voltage control of signal level and equal powered panning.

The module will work on +/-12 or +/-15 volts.

Description
Equal-power control of panning and cross-fading linear response assures that panning and percentage cross-fade behave predictably in response to a control voltage, eliminating signal level changes as well as annoying slow and fast areas. Equal Power control assures that the perceived loudness of the VCA's will remain constant at all positions of a signal in stereo or quadraphonic space.

Note that this sub-module processes control voltages only. No audio signal is handled by it directly. It requires CGS108 gain cells to function.

Construction


The circuit has been split over two PCBs, one containing the converter, the other the DC mixers.

An LM/CA3046 or LM/CA3086 transistor array has been used in the converter stage of the panner. Socket this chip as it can be fragile, and prone to self destruction. Transistor symbols on the PCB offer an alternative - to install regular transistors. These transistors would need to be matched See one of the other online resources for transistor matching, or follow the CGS simple transistor matching guide which will provide adequate results. Note that this discrete configuration has not been tested, and is offered only as a suggestion to experimenters.

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 the resistors first, followed by the IC sockets if used, then moving onto the taller components.

Take particular care with the orientation of the polarized components, such as electrolytics, diodes, transistors and ICs.

When inserting the ICs in their sockets, 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.

To install the header, slide the pins partially out of the plastic carrier strip so that you can solder the pins as close to the PCB as possible. (Some headers will not need the pins moved.) Before soldering, trim the portion of the pins that go through the PCB so they are just long enough to reach the other side. Once the header is soldered to the PCB, the carrier strip can be carefully clipped off as it is no longer required.

Alternatively, the pins could be fashioned from discarded component leads or tinned copper wire of an appropriate gauge. This option will not be as rigid as using a header.

There is no manual wiring on this module. All connections are made when the PCBs are soldered to the host PCB.

Setup
No set up is required.

Parts list
This is a guide only. Parts needed will vary with individual constructor's needs.

CC-BY-NC
Readers are permitted to construct these circuits for their own personal use only. Ken Stone retains all rights to his work. Serge Tcherepnin retains all rights to his work.