MXL 603S Mods
The MXL 603S suffers from low-quality parts in the circuit, and bad-sounding capsules.
But the shell is worth keeping. :) So long as you replace the capsule and circuit.
After 3 years' R&D, we have finally created a truly great small-diaphragm capsule. Available in both Cardioid and Omni varieties, these capsules are handcrafted and individually tested to meet exacting specifications.
The Cardioid capsule is voiced with a relatively flat response, to ensure sonic compatibility with a wide variety of sources. These capsules sound honest and rich, yet take EQ well. They lack the thin bass, the 5dB notch in the upper mids, and the grossly exaggerated highs of typical Chinese-made small-diaphragm capsules (such as can be found on most sub-$500 SDC microphones).
Needless to say, these capsules can be screwed onto the MXL 603S without tools. They work nicely with the stock circuit (and they work even better with our custom Schoeps replacement circuit).
Transformerless SDC Circuit Kit
This circuit kit was designed in-house as a drop-in replacement for the MXL 603S. It contains a full implementation of the Schoeps CMC5 circuit design.
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.
Read more about the Transformerless SDC Circuit Kit.