MXL CR78 Mods

The MXL CR78 is a small-diaphragm mic in a large-diaphragm body. It is nearly identical in its capsule and circuit implementation to the MXL 990, V250, 910, and 603S. All of these mics use a variation of the Schoeps transformerless circuit, and MXL's standard small-diaphragm capsule.

We do not recommend this mic in its stock form. The circuit often delivers good performance, although we have measured some that exhibited significant sonic anomalies (e.g. massive low-frequency rolloff in the circuit due to component problems). Also worth noting is that this circuit implementation is NOT a good platform for DIY upgrades; you'd need to replace the entire thing to create a high-performance microphone. Fortunately we have two sonically distinct DIY circuit kit options; see below.

The stock capsule tensd to have a lumpy frequency response in the 6k-12kHz range, resulting in non-musical boosts and cuts that cannot be fixed later via EQ.

We have multiple DIY upgrade options for this mic; the chassis and body could house five different capsule/circuit combinations, all of which will outperform most $1000 microphones.

We also have a mail-in mic mod service for the CR78, if you are interested in high performance but not interested in building the mic yourself.

#1: DIY Capsule Replacement

The circuit in the CR78 will work beautifully with our RK-47 and RK-12 capsules. It does provide appropriate polarization voltage for these capsules.

Both of these capsules will give the mic wider bandwidth and a smoother, more musical frequency response. With either of these capsules, the CR78 will need less EQ at mix time; tracks recorded with the modified mic will sound better and be easier to mix.

The CR78 circuit does not provide corrective EQ; therefore we do not recommend installing the RK-87 capsule unless you also install our MP-V57 circuit, which does allow for corrective EQ in the circuit.

#2: MP-V57 Circuit Replacement Kit (transformerless)

Our premium transformerless circuit, called the "MP-V57 PCB kit," fits the CR78 chassis. The V57 kit replaces 100% of the audio and DC circuits in the microphone, using uncompromising audiophile parts. It provides an internal switch that can be configured at build time as either a Cardioid/Omni pattern switch (assuming you've replaced the stock capsule with one of our dual-diaphragm models), or as a -10dB pad.

The circuit also provides the option of building corrective high-frequency EQ into the circuit, to make even the stock capsule sound more balanced and less sibilant. That said, we find our replacement capsules to offer superior sensitivity and self-noise performance, and smoother response overall.

Click for more info on the MP-V57 PCB kit.

#3: T-84, the transformer circuit replacement

To take your CR78 in a vintage direction, consider the T-84 circuit replacement kit. It is a design borrowed from Neumann's KM84. It will give your mic the tone of a vintage tube condenser, thanks to the ultra-simple signal path, carefully selected NOS JFET, and custom-wound output transformer.

Internal switches give your mic a second polar pattern (Omni) as well as a 10dB pad.

We recommend installing the RK-47 or RK-12 capsule with this circuit.

The photo at right shows the new circuit, which uses two high-quality two-layer PCBs manufactured in the US. This kit fits the MXL V63M, 440, V67G, and 2001, as well as the Apex 420 and 430.

Click for more info on the T-84 circuit kit.