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MICROPHONE OF THE MONTH MAY 2020

RTV 'MICROKIT' TUBE CONDENSER MICROPHONE

 

 

The first affordable condenser microphones came on the market around 1990; a solution for semi-pros and ambitious home studio owners.
Until then, good dynamic microphones were their only more or less affordable tool.

Yet, in the sixties, there was an alternative for those who were a bit handy: the Dutch firm RTV (Radio Technique Vollebrecht), from The Hague, had developed a high-quality kit for an omni condenser tube microphone: the Microkit. While a studio microphone cost about 500 guilders at the time, this kit had a much more modest price: 85 guilders.

Nowadays, many will be reluctant to build something like this themselves, but at the time there were many who welcomed the challenge to, for example, built a tape recorder or even an electronic organ.

The RTV package came with carefully machined parts, a preamp circuit board and its components, the capsule, everything for the external power supply and cabling plus a very clear manual. This allowed anyone who was a bit handy to solder the whole thing together in about six hours. Later, a perspex housing was also available.

Manufacturing the capsule was a precision job. For this, a foil sheet of aluminum-manganese-silicon, with a thickness of only 15 microns, had to be glued completely smooth to a pertinax ring. After drying, the membrane had to be tensioned by means of the six adjusting screws. This also had to be done very precise: too stiff a membrane gave bad bass and poor sound, too tight might result 'fluttering ' or a short circuit. The really skilled amateurs could replace the standard foil with gold foil, which resulted in an even better frequency response.

The microphone was intended for indoor use, but those who wanted could make a battery for outdoor recordings.

Abroad there was also interest in the RTV microphone, which was supplied as the 'Microkit' in countries such as England and Germany. For those who lacked the D.I.Y. gene, pre-assembled microphones could be bought

These and many more types feature in my book Witnesses of Words. More information about that can be found at www.witnessesofwords.com

wow cover

RTV condenser
RTV mic drawing
RTV Frequency chart

RTV see through

photo: internet

Top: the completed RTV Microkit tube condenser

Middle: pre-amp, frequency plot of an average amateur-built Microkit & perspex version

Below: capsule drawing, Dutch ad, UK sales leaflet, review and completed capsule

RTV capsule

Listen to the sound of the RTV Microkit:

RTV UK 1 RTV UK 2 RTV capsule
RTV ad
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