V72

V72 Tube Microphone Preamplifiers

The perfect partner for a tube microphone....

DESCRIPTION.
The V72 was developed 1953 at the NWDR (Nordwestdeutscher Rundfunk) as an universal studioamp with a fixed gain of 34dB to compensate the signal loss of passive filters and faders in modular studio mixers. It was designed to be used anywhere in the signal path from microphone input signals (preferably from high output tube mics like the Neumann U47) to full line amp applications. The high quality balancing transformers at the signal input and output and the mains transformer are shielded with multilayer mu-metal/copper technique.
The unit is fully self contained, it includes its own 220V power supply and all connections (as the mains supply and the balanced input and balanced output) are accessible through a single 12pin Tuchel connector. The 1uF capacitor in the input circuit creates a bass roll off and can be bridged for a smooth bottom end. The Pentodes Telefunken EF804S used in the V72 are common types and are still available.
The V72 was designed for exact 220V and is very critical with mains voltage. If used in the UK, AUSTRALIA or another country with higher mains voltage it has to be modified to run with the correct internal voltages. In countries with lower mains voltage a step up transformer has to be used.

THE V72 AS A MICROPHONE PREAMP.
The V72 can be used unchanged in combination with high output tube condenser mics as described above. Because there is no internal gain adjustment, the signal has to be attenuated if necessary either with a pad circuit before the input of the V72 or after the output. If the V72 is used with low and medium output microphones or on lower signals, it is necessary to modify the internal circuit of the V72 to get more gain than the default 34dB. If this is done properly, the V72's original character is unchanged in any gain setting.

SPECIAL V72/55 VERSION.
After long researches and carefully considering existing methods, I developed several modifications for the V72. The idea was to combine the V72's original character and warmth, linear frequency response and excellent noise figures with some missing features of the original unit.

I offer a limited number of V72 as a special version V72/55which includes the following features:
(Please note that all V72/55 are fully restored and tested and come with a test protocol and an individual frequency plot. There is a 12 month warranty on the tubes of this units).

(Sorry, no units available at the moment)

extended gain to 55dB
6-step high quality step rotary switch for gain control, operated from the front panel (+25/+35/+40/+45/+50/+55 dB).
switchable internal +48V phantom power to IEC 268-15/DIN 45596
extended frequency response 8Hz to 32kHz
cable connection from a special 12-pin Tuchel to audio in/out (XLR balanced, pin 2 hot) and mains
240V version on request

contact us here

Supersonic V72/55 special version:

Any V72 for sale? click here to go to the "For Sale" section

Circuit diagram of the V72: See or print V72' s original circuit diagram

Many thanks to:
Graeme J. Cohen (Valve Research) Athelstone/Australia
Institut fuer Rundfunktechnik/Freimann
Bayerischer Rundfunk/Muenchen
SRT / Nuernberg
Walter Niederreith/Stuttgart

Last modified: May 2009