Product Description

The UM 900 is the first switchable pattern, tube condenser microphone that can be connected to industry standard 48 Volt phantom powering using a regular 3-pin XLR-microphone cable. This is made possible by an advanced circuit design for the amplifier and internal power supply.

The pickup capsule uses a traditional, proven design with two large, gold plated plastic diaphragms.

Three switches are located around the body of the UM 900. The switch in the front selects the polar pattern: omni, wide cardioid, cardioid, hyper cardioid and figure 8. Located 120 degrees to each side are switches for gain adjust and low frequency roll-off.

The unusual shape of the microphone’s body is especially designed to minimize undesirable sound reflections toward the pickup element.

Acoustic influences that could result from the housing resonance and/or mechanical vibration are reduced by the robust construction and by a special fixture within the microphone’s housing that dampens vibration.


The high sensitivity and low noise of the UM 900 make it especially suitable for vocal and speech pickup in professional sound recording studios, scoring stages and broadcast studios. The 5 pickup patterns allow the microphone to be used for a wide variety of applications. E.g. the microphone can be used as an overall pickup for a large orchestra or as a solo or spot mike for individual instruments. It can also be used as an announcers microphone where its proximity effect is desirable.


The direction of maximum sensitivity is radial to the microphone body, i.e. side addressed. The front of the microphone is indicated by the model number and the pattern selector switch.
The pick-up capsule is mounted in a large, acoustically open headgrill that prevents mechanical vibration interference.

This gives the microphone a clean, colourless sound characteristic.


The internal vacuum tube amplifier of the UM 900 can be powered by any external 48 Volt phantom supply that can provide at least 4 mA of current.

The amplifier uses a specially selected vacuum tube.
An internal transverter provides all the necessary voltages.
The low impedance output is implemented with an operational amplifier and balanced output transformer.

The UM 900 can be connected with cables up to 150 m length without any effects on sound quality.

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Additional Information

Polar patterns

omni, wide cardioid, cardioid, hypercardioid, fig-8

Acoustical operating principle

Pressure gradient transducer

Large diameter diaphragm capsule

dual diaphragm

Frequency range

40 … 18000 Hz

Sensitivity at 1 kHz

25/ cardioid 40 mV/Pa

Level selector switch

-10/ cardioid +4 dB

Switch position "reduced bass roll-off" at 70 Hz

-10 dB

Output impedance

30 Ω

Dynamic range

114 dB

Current consumption (P 48, DIN 45596, IEC 268-15)

4 mA

Output connector

3-pin XLR-connector
goldplated contacts

Sub-miniature tube

low-noise version



Dimensions (L x )

200 mm x 75 mm

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