MXL 991 Mods

The MXL 991 is an inexpensive pencil condenser with a few significant barriers to great performance.

The small-diaphragm capsule is hit-or-miss; some sound good, but some do not. If you wish to mod this mic, plan to buy a few capsules so that you can keep the best-sounding one.

The other problem is that the circuit is built with inexpensive, indifferent parts, resulting in mediocre performance. We have created a drop-in replacement circuit board kit with a few surprise extras.

Transformerless SDC Circuit Kit

transformerless circuit kit

We make our own custom 2-layer PCBs in the US, and provide a complete circuit's worth of handpicked and matched components. The result is linear from 20Hz–20kHz, with very low self-noise and distortion. It provides a full 60VDC to polarize the capsule.

Two build-time options are provided to allow personalization of the mic:

  • Pre-pad the mic by 6dB without adding capacitors. If you plan to use the microphone primarily on high SPL sources, use the included parts to cut the mic's sensitivity by 6dB via a noncapacitive pad option.
  • Roll off the highs to correct for an over-bright/peaky capsule, or as a darker mic for taming bright/thin sources.

Read more about the Transformerless SDC Circuit Kit.