Archive for secret weapon

4 Channel Mic Pre & Limiter

Posted in Modded, Racked Modules with tags , , , , , , , , on December 31, 2013 by AnalogAudioRepair

Another fun project for engineer and lover of odd gear, Dan Physics.  He dubbed it the Mic RipPre 4.  These are funky little portable mic preamps with opto limiters that were designed to run on two 9v batteries.  They have Beyerdynamic input transformers and 600 ohm output transformers.  I gutted four of them, recycling the XLR connectors and circuit boards, and fit them in a 1U rack case with a +/-15v power supply and +48v phantom power.  The only other mod was a control for the amount of limiting.  It’s not exactly threshold, nor is it really ratio – just “amount”.

They are pretty clean sounding preamps, no surprise with such a simple circuit.  All new capacitors didn’t hurt either.  One board needed a new diode in the limiter, but otherwise they were in good shape.  Fitting all of the controls on the front panel was the hard part!  The original preamps had nice little collars around the toggle switches so I used those to prevent accidents with phantom power.

mic preamp/opto limiter

Stripped down boards

laying out 4 channel mic preamp/opto limiter

Making sure it will fit.

mic preamp/opto limiter control panel layout

Control layout

hand drilling panel for mic preamp/opto limiter

Why I need a Drill Press

wiring 4 channel mic preamp/opto limiter

All wired up

4 channel mic preamp/opto limiter

Completed unit

knobs and switches

Controls

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