Flea SM 204/23

The FLEA SM 204/23 is a premium multi-pattern valve condenser microphone that recreates the exceptionally rare Siemens SM204/23, combining a FLEA CK12 capsule, 6072A valve, V2545 transformer replica, 30 Hz to 20 kHz frequency response, 7 mV/Pa sensitivity and cardioid, omnidirectional and figure-8 polar patterns with modern, hand-built construction.

FLEA developed the SM 204/23 to reproduce the distinctive sonic behaviour of the original Siemens microphone while delivering the consistency and reliability expected in a contemporary professional recording environment. The design retains the key elements responsible for the classic microphone's reputation, including its CK12-style capsule architecture, valve electronics, self-biasing circuit and unusual V2545 output transformer.

Classic Siemens SM204/23 Character

The original Siemens SM204/23 earned a reputation for natural detail, musical midrange and a controlled tonal balance that suited demanding studio recording. Original examples have become extremely scarce, making their characteristic combination of valve circuitry, capsule and transformer increasingly difficult to access.

FLEA recreates this design rather than simply borrowing its visual identity. The SM 204/23 combines the company's CK12 capsule with carefully developed electronics and a replica of the Rohde & Schwarz Henry V2545 transformer to reproduce the depth, harmonic character and transient response associated with the original microphone.

FLEA CK12 Capsule

The FLEA CK12 capsule forms the acoustic heart of the SM 204/23. FLEA designed it to capture the character associated with the original CK12 capsule, giving the microphone a detailed yet smooth top end, substantial midrange and controlled low-frequency response.

Its multi-pattern construction supports cardioid, omnidirectional and figure-8 operation. This flexibility allows engineers to adapt the microphone to different sources, room acoustics and stereo recording techniques without sacrificing the core tonal character of the design.

6072A Valve Circuit

The SM 204/23 uses a 6072A valve as standard. Its valve circuitry contributes harmonic complexity and a smooth response while retaining the detail and dynamic articulation required for professional recording.

FLEA also offers a GE 6072A valve upgrade for engineers who want an alternative premium valve option. The microphone's self-biasing circuit represents another important element inherited from the classic design. It helps the electronics accommodate high sound pressure levels with generous headroom, making the microphone particularly capable when recording powerful and highly dynamic sources.

V2545 Transformer Replica

A replica of the Rohde & Schwarz Henry V2545 output transformer forms a defining part of the SM 204/23 signal path. FLEA recreates the original transformer's design and materials to retain the tonal depth, harmonic richness and controlled low-frequency response that contributed heavily to the character of the Siemens microphone.

Rather than substituting a generic modern transformer, FLEA uses the V2545 replica to preserve one of the most distinctive components of the original circuit.

Three Selectable Polar Patterns

The SM 204/23 provides cardioid, omnidirectional and figure-8 polar patterns, selected through the supplied power supply. Cardioid focuses capture towards the front of the microphone and reduces sound arriving from the rear, making it particularly useful for vocals and individual instruments.

Omnidirectional operation captures sound from all directions and allows engineers to incorporate more of the recording space into the result. Figure-8 captures sound from the front and rear while rejecting the sides, supporting applications such as Mid-Side and Blumlein recording as well as controlled room and dual-source techniques.

Sound and Recording Applications

The SM 204/23 delivers a natural tonal balance with a rich midrange, smooth high-frequency response and solid, controlled bass. Its ability to reproduce low-level detail and fast transients makes it suitable for sources where engineers need both character and accuracy.

Its combination of valve circuitry, high-SPL composure and selectable polar patterns makes it particularly well suited to lead and backing vocals, spoken word, acoustic instruments and ambient recording. The three-pattern architecture also gives engineers considerably greater control over room contribution and microphone placement than a fixed-pattern design.

Technical Performance

The FLEA SM 204/23 covers a 30 Hz to 20 kHz frequency range and provides 7 mV/Pa sensitivity at 1 kHz. It offers rated impedance options of 50 or 200 ohms, with corresponding minimum rated load impedances of 500 or 2,000 ohms.

These specifications combine with the CK12 capsule, 6072A valve circuit and V2545 transformer to create a microphone aimed firmly at professional studios seeking classic valve-microphone behaviour rather than a neutral, transformerless condenser presentation.

Complete FLEA SM 204/23 System

FLEA supplies the SM 204/23 as a complete recording system. The package includes the microphone in a wooden box, an external power supply with integrated polar-pattern selection, a microphone-to-PSU cable with swivel mount connector, power cord, microphone dust cover and printed manual. FLEA packs the complete system in a protective hard carton with a foam insert.

FLEA handcrafts the SM 204/23 in small production batches using premium components. Each unit undergoes individual measurement, testing and final inspection, bringing the architecture and character of an exceptionally scarce vintage microphone into a newly manufactured professional studio system.

Why Choose the FLEA SM 204/23?

• Access an exceptionally rare microphone concept: It provides a practical route to the character of the Siemens SM204/23 without relying on finding and maintaining a scarce vintage original.
• Capture vocals with depth and character: The CK12 capsule, 6072A valve and V2545 transformer architecture combines detail with the harmonic richness associated with classic valve microphones.
• Record powerful sources confidently: The self-biasing circuit provides the composure and headroom required for loud, dynamic performances.
• Adapt quickly to different sessions: Cardioid, omni and figure-8 patterns make the microphone useful across close recording, room capture and specialist stereo techniques.
• Invest in a complete studio system: The supplied PSU, dedicated cable, wooden microphone box and accessories provide the core components required for professional operation.
• Gain vintage character with modern manufacture: Small-batch construction, individual testing and newly manufactured components remove many of the uncertainties associated with ageing vintage microphones.

• Faithful recreation of the rare Siemens SM204/23 studio microphone
• FLEA CK12 capsule developed to reproduce classic CK12 sonic characteristics
• EH 6072A valve fitted as standard
• Optional GE 6072A valve upgrade
• Replica of the Rohde & Schwarz Henry V2545 output transformer
• Self-biasing valve circuit designed for excellent headroom on high-SPL sources
• Cardioid, omnidirectional and figure-8 polar patterns
• Polar-pattern selection from the external power supply
• 30 Hz to 20 kHz frequency response
• 7 mV/Pa sensitivity at 1 kHz
• 50/200-ohm rated impedance
• Minimum 500/2,000-ohm rated load impedance
• Rich midrange with smooth high-frequency reproduction
• Solid and controlled low-frequency response
• Detailed transient and low-level dynamic reproduction
• Suitable for vocals, spoken word, acoustic instruments and ambient recording
• Supports versatile room capture and stereo recording techniques
• Handcrafted in small production batches
• Individually measured, tested and inspected
• Supplied with dedicated external power supply
• Includes microphone-to-PSU cable with swivel mount connector
• Includes wooden microphone box, power cord, dust cover and printed manual
• Complete system supplied in a protective foam-lined product carton

This item, like everything we supply, comes with the complete support of our expert team. Our excellent technicians have been specifying, building and supporting studios for over twenty years. If you have any problems with installation, setup or everyday use, they’re never more than a click away, and always happy to help.

You can contact them here.