Microtech Gefell M990

A Tube Microphone Designed for the Constraints of Radio and the Richness of Ensembles

The M 990 follows the great tradition of tube condenser microphones used in production and broadcasting, where reliability and intelligibility are paramount. It is particularly suited for challenging radio activities and orchestral recording, two contexts that require both natural rendering, controlled presence, and the ability to handle significant dynamic range. The design highlights a new capsule and a tube preamplifier with a proven architecture to achieve a sonic character that is both expressive and usable in a modern mix.

Intended Users and Applications in Studio or Live Recording

The M 990 is aimed at sound engineers, production studios, demanding podcasters, and control rooms seeking a high-end vocal microphone capable of enhancing timbre without harshness. Thanks to its cardioid pattern and sensitivity, it is suitable for spoken voice recordings (radio, dubbing, voice-over) as well as singing voices, limiting room pickup while maintaining airiness. In orchestral setups, it can serve as a section microphone, spot mic (woodwinds, brass), or close ambiance mic when a stable image and clear midrange are desired. Its tube signature is also relevant on demanding acoustic sources whenever body and a sense of depth are wanted without overemphasizing sibilance.

Design, External Power Supply, and Key Points for Clean Integration

The core of the M 990 is a capsule equipped with a large gold-plated plastic diaphragm, designed to capture details generously, with a stated frequency response of 40 to 18,000 Hz. The tube preamplifier uses an EF 86 (pentode configured as triode) selected for its sonic qualities, providing the typical tube circuit depth while maintaining good definition.

Power Supply N 920.1: Stability, Connectivity, and Mains Adaptation

The microphone operates with an external power supply N 920.1 (essential for a tube microphone), responsible for delivering the necessary voltages, including a continuous voltage supply rated at 120 V. The unit accepts mains voltages of 115 V or 230 V and frequencies of 50 Hz or 60 Hz, suitable for fixed studio use or live performance. It features a power on/off switch, a microphone output via 7-pin Tuchel connector, and an audio output via 3-pin XLR, with an integrated mains voltage selector. For long cable runs, a recommendation is provided: beyond 50 meters, it is advised to have the filament voltage adjusted by a technician to 5.8 V to maintain optimal operating conditions.

Sound Capture: Headroom, Noise, and Dynamics

With a maximum SPL rated at 119 dB (for total harmonic distortion less than or equal to 0.5%), the M 990 can handle strong sources without collapsing, which is appreciated on brass, light percussion, or powerful voices at reasonable distance. The self-noise is given according to two measurements (CCIR and A-weighted), and the signal-to-noise ratio is also specified, useful information for choosing a microphone suited to very detailed recordings (close vocals, classical, ambiance). The overall aim is a coherent studio compromise: tube musicality, level of detail, and dynamic reserve.

Technical specifications

Frequency response - start	40 Hz	Capsule	Large Diaphragm
Frequency response - end	18 kHz	Connection	XLR
Category	studio microphone	Color	Black
Directivity	cardioid

Polar pattern	cardioid	Weight	400 g
Acoustic operating principle	pressure variation transducer	Dimensions	185 mm x 43 mm
Frequency response	40 to 18,000 Hz	Mains voltage	115 V or 230 V
Sensitivity at 1 kHz	15 mV/Pa +/- 3 dB	Mains frequency	50 Hz or 60 Hz
Nominal impedance	200 ohms	Controls and connectors	power on/off switch, 7-pin Tuchel connector (microphone), 3-pin XLR connector, integrated mains voltage selector
Noise level	CCIR 468-4 24 dB	Long cable run recommendation	beyond 50 meters, have the filament voltage adjusted by a technician to 5.8 V
Signal-to-noise ratio (1 Pa at 1 kHz)	CCIR weighted measurement 70 dB	M 990 tube microphone in wooden case (length x depth x height)	275 x 90 x 70 mm
Maximum SPL for total harmonic distortion <= 0.5%	119 dB	Dark bronze finish	reference 211160
Total dynamic range of microphone preamplifier	106 dB	Satin nickel finish	reference 211136
Continuous voltage supply	120 V	Matte black finish	reference 211137
Anode current	1 mA	Windscreen W 92, anthracite	reference 202402
Filament voltage	5.8 V	Black pop filter PO 70	reference 600018
Filament consumption	200 mA	Dark bronze microphone stand MH 80	reference 202322
Tube	EF 86	Connection cable with swivel mount C 92.1 S	reference 202206
Output connector	7-pin Tuchel connector C 70/A	Aluminum transport case Case 1	reference 702001