The MXL 990 is a small-diaphragm, fixed-cardioid, transformerless FET condenser with an externally-biased 17mm gold diaphragm (in a 22mm-diameter capsule).
The circuit is MXL’s version of the famous Schoeps transformerless circuit, which uses a FET input and a pair of bipolar transistors to produce a balanced output without a transformer. The same circuit can be found in numerous other MXL mics, such as the 2006, V63M, V57, and 603S/604.
The small-diaphragm capsule is the same as is found in most of MXL’s small-diaphragm mics, including the 603S/604 and MCA SP-1. In the 990 (and SP-1), the capsule is mounted within a brass baffle ring that affects the capsule’s frequency response and polar pattern.
As a part of MXL’s “900 Series,” this mic is distributed exclusively by Guitar Center and its various online sales divisions.
As a vocal mic, the MXL 990 produces a subjectively neutral and nicely balanced sound with just a hint of high-end sizzle that can help out vocalists who have difficulty getting the definition they need.
Beginning in Q1-2013, MXL transitioned the 990 circuit board to a surface-mount design, making the mic a poor candidate for DIY circuit upgrades, unless the entire circuit board is replaced with thisMXL 990 PCB upgrade kit.
The photo at right shows the surface-mount 990 circuit board.
Owners of the older through-hole circuit boards are encouraged to investigate the numerous modification options for this microphone; see the sidebar listing.
The mic is an excellent platform for a capsule swap; replacing the stock small-diaphragm capsule with any of a variety of large-diaphragm choices will audibly revoice the microphone, and lower its noise floor.
Capsule wiring guide for modders: the black wire attached to the brass baffle is connected to the capsule diaphragm. The red wire attached to the center terminal behind the capsule is connected to the backplate.