The evolution of microphone technology is marked by numerous innovations, some realized and others left to the imagination. One such intriguing concept is the development of a microphone centered around the RK-12 capsule—a component inspired by the legendary CK-12 capsule used in iconic microphones like the AKG C12 and Telefunken ELA M251. This article delves into a hypothetical design, exploring how the RK-12 capsule could be integrated into a unique microphone circuit, and the potential implications for modern audio applications.

The Legacy of the CK-12 Capsule
To appreciate the significance of the RK-12 capsule, it’s essential to understand its predecessor, the CK-12. Renowned for its distinctive sonic characteristics, the CK-12 capsule contributed to the warm, airy, and detailed sound of classic microphones. Its edge-terminated design and dual-diaphragm construction allowed for multiple polar patterns, making it versatile for various recording scenarios.
Introducing the RK-12 Capsule
The RK-12 capsule is a modern reproduction aimed at capturing the essence of the original CK-12. Manufactured with precision, it seeks to emulate the frequency response and transient behavior that made the CK-12 a favorite among audio professionals. Integrating the RK-12 into a new microphone design presents an opportunity to blend vintage tonal qualities with contemporary engineering advancements.
Conceptualizing the Microphone Circuit
In this thought experiment, we envision a microphone circuit that leverages the RK-12 capsule’s capabilities while incorporating modern components to enhance performance. The design focuses on achieving low noise, high fidelity, and flexibility in polar patterns.
1. Impedance Conversion
A critical aspect of the microphone circuit is the impedance converter, which interfaces between the high-impedance capsule and the subsequent amplification stages. Utilizing a high-performance operational amplifier (op-amp) can provide the necessary impedance matching with minimal noise contribution. For instance, the OPA series op-amps are known for their low distortion and wide bandwidth, making them suitable candidates for this application.
2. Polar Pattern Selection
To harness the dual-diaphragm nature of the RK-12 capsule, the circuit can incorporate a mechanism for selecting different polar patterns, such as cardioid, omnidirectional, and figure-eight. This can be achieved through a combination of electronic switching and varying the voltage applied to the backplate of the capsule.
3. Power Supply Considerations
Ensuring a stable and clean power supply is paramount for microphone performance. Implementing a well-regulated phantom power circuit with adequate filtering can minimize noise and provide consistent operation.
Potential Applications and Benefits
Designing a microphone around the RK-12 capsule with the aforementioned circuit features could offer several advantages:
Versatility: The ability to switch between polar patterns allows the microphone to adapt to various recording environments and sources.
Vintage Sound with Modern Reliability: Capturing the sought-after characteristics of the CK-12 while benefiting from contemporary electronic components enhances both sonic quality and durability.
Cost-Effectiveness: By utilizing modern manufacturing techniques and components, such a microphone could offer high-end performance at a more accessible price point.
While this microphone remains a conceptual exploration, it underscores the potential of combining classic design elements with modern technology. The RK-12 capsule serves as a bridge between the revered sounds of the past and the innovations of the present, offering exciting possibilities for future microphone designs.