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This microphone pre-amplifier was designed originally for portable recording (although it would be equally at home in a studio, or mixing desk). To this end (with the exception of the high pass filter) it is as neutral as possible, with no EQ, as it is expected any processing or EQ would be done in post production.
This comes on two parts, the microphone Pre-amplifier board, and the level meter board.
The Pre-amplifier itself is based on an SSM2017 or INA217 with Servo-null provided by IC2A, then followed by a third order Butterworth High pass filter. Input options include a 10dB pad, phantom power and Invert. IC2B is a precision half wave rectifier which feeds the VU meter PCB.
Shown
above is the full 12 LED meter, note greyed out components are for
other options, such as the rectifier, which is not needed in this
case as there is one on the pre-amplifier board. Other options allow
you to build the VU meter with either 4, 8 or all 12 LEDs.
I have
also made up a spreadsheet (with Open Office) for calculating
resistor values for the VU meter, available here as an OpenDocument
spreadsheet.
Purchase
Unfortunately
the cost of Electronic components and shipping from Australia is not
cheap, so I am selling these as short form kits (PCB, Instructions
and any programmed parts) rather than complete kits.
At
the moment I am selling these through Ebay which for
this project includes:
PCB and Assembly
instructions (PDF)
Email
for more details.
Copyright
© 2011 Australian Technical Production Services
