A simple but effective four channel mixer
for use with control voltages and audio. Each channel has an
independent level control that goes from fully off to unity gain.
Two outputs are provided. OUT (MAIN) is a
low impedance driver that simply presents the sum of the input
signals as controlled by the level pots. The other, OUT (SOFT),
is also the sum of the inputs but this time the signal is passed
through a special ‘soft clipping’ circuit. This soft clipper is
designed to sound like an overdriven valve amplifier and adds a
form of harmonic distortion that is musically interesting.
If no jack plug is inserted into the IN 3
socket then by adjusting the LEVEL 3 pot you will add a positive
offset voltage to the output. Likewise, if no jack plug is
inserted into IN 4 then the LEVEL 4 pot will control the amount
of negative offset that is added to the output. Each pot
therefore can either act as a constant voltage source which can
be added to other CVs for controlling other modules. Furthermore,
it can also be used to generate asymmetrical signal clipping in
either any following modules or by using the soft output of the
Fourmix itself.
The module also features two output level
LEDs. These monitor the signal level at the main out socket. The
5V LED lights when the signal exceeds +/-5V and indicates that
soft clipping is about to take place from the soft output. The
peak LED lights when the output signal is getting near hard
clipping, ie. around +/-11V. Special circuitry is employed to
ensure the LEDs do not cause power supply clicks when they turn
on or off.
The module accommodates either our standard
Oakley/MOTM power header or a Synthesizers.com power header.
Current consumption is approximately 25mA per rail.
The issue 2 PCB is 75mm (deep) x
124mm (height). The four pots are normally board mounted for
speed and simplicity
As with all Oakley projects the
PCB is double sided with through plated holes, has tough solder
mask both sides, and has bold component legending for ease of
construction.
The issue 1 Oakley Fourmix as a single
width MOTM format module in a natural finish Schaeffer panel.
Note also the use of our optional Sock6 socket board to help keep
the wiring to the sockets neat and tidy. Issue 2 boards are
similar.
Project Downloads
Construction
Guide Our handy guide to building
Oakley DIY projects
Parts
Guide Our handy guide to buying
parts for Oakley DIY projects.
Schematics are available to
purchasers of the PCBs and will only be sent via e-mail when the
board(s) are shipped.
Front Panel database
A Schaeffer front panel can be made for
this module. The databases can be found by downloading the
following links:
5U format 1U wide
Fourmix module in traditional black
5U format 1U
wide Fourmix module in natural finish
To read these files you will need
a copy of ‘Frontplatten designer’ from Schaeffer. The program also features on-line ordering, so its
now even easier to buy your panels from Scheaffer.
The company are based in Berlin in Germany
and will send out panels to anywhere in the world. Delivery to
the UK normally takes around ten days. For North American users
you can also order your Schaeffer panels from Front
Panel Express.
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