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Microphone Parts RA-23

Pricing & Availability

  • MSRP: $269
  • Discontinued


RA-23 Documentation

OmnidirectionalCardioidMicrophone Parts RA-23

Multi-Pattern Condenser Microphone

The RA-23 is a dual-pattern FET condenser that was sold as a DIY microphone kit. It has since been repackaged and renamed for the type of capsule included; the new versions (as of 2015) are called the S-47, S-12, and S-87.

RA-23 Cutaway ViewThe kit includes a transformerless circuit based on the Schoeps CMC-5. The two PCBs are made in the USA. The components include matched capacitors, specially selected and pre-biased Siliconix J305 JFET, low-noise Hitachi output transistors (also matched), and precision resistors.

The PCBs were designed to fit easily with the enclosed body, which is aluminum (anodized in black), with a tapered grille made of 2 layers of brass mesh. The use of two layers of different-gauge mesh offers a good compromise between plosive protection (in which more layers are beneficial), resonance reduction (ditto), and minimization of sonic reflections (in which fewer layers, and a more open weave would be preferred).

Any of 5 large-diaphragm capsules can be selected, including K47, K67, and CK-12 types. The capsule choice affects sensitivity and frequency response, but in all cases the sensitivity would be at least 27mV/Pa (and possibly as high as 45mV/Pa), and self-noise would be below 13dBA.

The polar pattern switch on the PCB removes the capsule’s rear diaphragm from the circuit entirely when in “True Cardioid” mode; this raises the sensitivity of the mic by ~4dB in Cardioid as compared to Omni.

The kit includes: microphone chassis and body, capsule mount, capsule, PCBs (unpopulated), all components necessary to build the circuit, US-made silver/teflon hookup wire, and a zippered storage pouch.

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The mic was released in 2014.


Pickup Patterns Pads & Filters
Omnidirectional (23 mV/Pa; 20 - 20,000 Hz)
Cardioid (27 mV/Pa; 20 - 20,000 Hz)
Capsule Dimensions Impedance SPL/Noise
Diaphragm diameter: 26mm
Capsule diameter: 34mm
Diaphragm gauge: 3 microns
Weight Length Max Diameter Interface(s)
290g (10.23oz) 184mm (7.24'') 50mm (1.97'')
  • 3-pin XLR male (1)
Power Specifications
  • Requires phantom power
  • Phantom voltage: 48 ± 4v

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