Voltage Controlled Mixer Channel (Stereo Mixer)
Voltage Controlled Stereo Mixer
The VCSM is an expansion of my Equal Power Panner with VC Gain added. The module swaps the THAT 2180 chips with THAT 2162 dual gain cells
My build is a 4 channel mixer with Master Level out
Each channel has MANUAL and VC PAN, MANUAL GAIN, VC GAIN (VCA) and a variable VCA response, manually adjusted from Linear to Exponential
Auxillary inputs are provided on the output mixer to add additional inputs
The module is built with Voltage Controlled Mixer Channel PCBs and a small output mixer board
Build Notes
Current build is Version 1.0
Mixer channel (preliminary docs)
BOM:VCMC BOM
Schematic:VCMC Schematic
PCB guide - component values : component values
Output Mixer PCB
BOM: -------------
Schematic output mixer PCB:Output Mixer Schematic
Notes on building: -------working on it---------
PANELS:There's no matching panel from me because it's up to the builder to decide how many channels to make. The module is 1" wider than the number of channels with the extra inch having the outputs, master level control, and AUX INs
I've included the artwork here (PDF and Illustrator files) and the Front Panel Express file I used as seen below.
Download FPE File, AI Layout and artwork PDF:Download
Trimming the pan circuit and exponential VCA gain
PCBs: There is a dual footprint for the THAT2162 chip. The smaller fits the THAT chip and the larger the COOLAUDIO version
There are 4 51R resistors on each 2" board. Use them with the CoolAudio 2162 chips. If using the THAT chips, leave them off.
Each 2" PCB is 2 mixer channels. I also have single channel 1" PCBs for building with an odd number of channels. One 2162 chip will have an unused package when building the 1" boards.
PCB sets include a main PCB and a matching panel component PCB
Dual Channel PCB and Panel Component PCB
Single Channel PCB and Panel Component PCB
Output Mixer PCB
Using a single VCA channel output op amp: Daisy-chain the gain cells to a single op amp
All the 2162 gain cells can be summed to a single op amp current to voltage converter. Fit the op amp and its pasive components on one channel. The device and its components are in the white outline shown. Leave those components off all the other channels. Pads are provided for daisy chaning the 2162 outputs to the channel with the op amp. Then send that output to the output mixer PCB.
Be careful not to use the power trace vias by accident! They're the same size as the pads.
Wired connection to a single op amp
Connecting mixer channels to the output mixer
The pads labeled "OUT BUS" carry the channel output to the panel PCB. Connect these pads to the output mixer PCB inputs. When using a single current to voltage op amp connect only one.