recordinghacks

MXL 7000

Cardioid Condenser Microphone

The MXL 7000 is a fixed Cardioid condenser built into a vintage styled, yoke-mount housing that appears to be based on the RCA 77DX.

The mic’s circuit is transformerless, primarily built with surface-mount components, including three ICs. Several transistors, including the 2SK170 JFET, are through-hole components, as are several Nichicon branded electrolytic capacitors.

The capsule appears to be one half of MXL’s standard 32mm K67, although built with a 3-micron diaphragm. The rear backplate is not a standard K67, but rather a new acoustic delay component that was presumably designed to alter the capsule’s frequency response.

Our analysis of the circuit revealed linear frequency response and low distortion. The test was done with a signal injection rig. It revealed no low- or high-frequency filtering. Distortion performance was on a par with a well-built transformerless design.

Capsule polarization in the sample microphone was 63VDC. The capsule was direct coupled to the JFET gate, without a blocking capacitor. High-impedance leads are soldered directly to the PCB, rather than insulated from the board on terminals.

An acoustic sweep revealed relatively linear response, plus or minus 1.5dB across most of the spectrum. Notably, this microphone failed to exhibit the 3-5dB peak around 10kHz that is seen and heard in most MXL LDCs. The alternative backplate design of the capsule is likely responsible for this flatter frequency response.

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Specifications

Pickup Patterns	Pads & Filters
Cardioid (8.9 mV/Pa; 20 - 20,000)

Capsule Dimensions	Impedance	SPL/Noise
Diaphragm diameter: 25mm Capsule diameter: 32mm Diaphragm gauge: 3 microns	200 Ohms (Low)	Self-noise: 13.0 dB(A)

Weight	Length	Max Diameter	Interface(s)
n/a	180mm (7.09'')	65mm (2.56'')	3-pin XLR male (1)

Power Specifications

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