MXL 992 Mods
The MXL 992 is a traditional Chinese-style condenser mic: linear transformerless circuit, peaky K67 capsule. The good news is that three of the first couple things you'd want to do to "mod" it are already done for you. The bad news is that there is still room for improvement, and that making those changes is harder than it should be.
Here is the good news:
- There's no cheap ceramic input coupling cap. The capsule is coupled directly to the JFET gate.
- The polarization voltage isn't too low (as is true on most transformerless MXL mics). The one we saw was set to 70VDC, which is arguably higher than it should be. Further, capsule polarization voltage is easily changed via the trimpot on the main circuit board.
- The main signal caps are already film types.
Now for the bad news: the capsule is a bad match for this circuit. And the circuit is compromised in several ways, causing the noise floor and distortion to be higher than they should be.
Here is what we recommend:
#1: Capsule Replacement
The MXL 992 capsule is a 32mm K67 type; while not necessarily terrible, it tends to have a peaky response that is not well-suited to the mic's circuit.
Normally we would recommend installing the RK-47 or RK-12, but neither of these will fit the 992's saddle. Installing either would require one of these two solutions:
- Drill holes into the 992's capsule deck to accommodate the mounting post that is included with the new capsule. (We have not done this, and cannot say whether it is feasible.)
- Drill holes into the existing saddle arms to accommodate the tapped holes in the RK-47 or RK-12. (We have not done this, and cannot say whether it is feasible.)
#2: 992 Mini-Mod
For advanced modders only, we have assembled a set of handpicked components to upgrade the most critical parts of the 992's audio circuit. It includes a new low-capacitance JFET that is better suited to the 992's circuit than the stock 2SK170. It includes handpicked bias resistors for the new JFET. It includes a new low-noise 1G resistor, which is easily changed when the JFET is replaced. It includes premium silver/Teflon audiophile wire to replace the mic's internal wiring. Finally, it includes a set of six Wima film caps to replace all the signal capacitors in the microphone.
This kit does not include our standard photo tutorial/documentation. Rather, it includes only a simple text document describing where the replacement parts are to be installed, plus a few color photos to confirm details. This kit is intended for experienced DIY enthusiasts only.
Click to read more about the 992 Circuit Mod Kit.
Alternatively, we can modify your 992 for you; contact us for details.
#3: Grille Replacement
Our custom, handmade headbaskets for the MXL 770 also fit the 992... more or less.
Caution: you might need to use a metal file or Dremel tool to shave off the metal tab that protrudes from the capsule deck (the flat metal plate onto which the capsule is mounted). Without this adjustment, the new 770 grille won't fit the 992 chassis properly. Click the thumbnail at left to see a photo of a properly filed metal tab.
The Cardioid symbol on the 770 grille faces the rear side of the 992, once installed. You can remove the small black silkscreened icon with a razor blade.
Click for more information on replacement grilles for the MXL 992.