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Mu Phone logo

Amroh- (American Radio House), was a trading company, founded in 1929 and located in Muiden.

The company sold radios and radio parts and would later also make tape recorders. Every Dutchman who was interested in electronics knew the Amroh products.

Well before Amroh started producing and selling wire-recorders and, around 1950, the first tape recorders were made, microphones were already being made, to their own design.

The M 419 and M 420 date back to 1942, so they were produced during the occupation by Nazi Germany. Possibly the martial name was also a result of that occupation.

Ball-shaped microphones were introduced in the United States in the late 1920s; they were condenser type microphones for sound film, they were called 'The Bomb', for obvious reason. The round shape was thought to be the ideal design, allowing sound waves to reach the element with as little reflections from the casing as possible.

A decade later a dynamic microphone with a spherical shape was produced: the Western Electric 630 'Eight Ball'.

The variants from Muiden had a diameter of 7.5 cm and were equipped with a crystal element that was spring-mounted horizontally in the casing, to make the microphones reasonably shock-resistant.

Both types were omnidirectional (sensitive all around) and intended for speech amplification.
The M 419, was heavy nickel plated and had a fixed cable, the M 420, in black crystal lacquer and embellished with nickel bands, had an element of 'unprecedented quality' and was intended for 'gourmets', it had an Amphenol MC1 screw connector, so it could be used with interchangeable cables.

Both microphones were probably only produced in small numbers: apart from my copies I have never seen any other M 419 or M 420s, so they are extremely rare, these 'Ears of the World'.

Many more types feature in my book Witnesses of Words. More information about that can be found at

wow cover


Mu Phone M419 & M420
Mu Phone name

Above: Mu Phones, M 419 and M 420 and script on the M 419

Below: sound, Ad from 1942 and the 'floating' element

Listen to the sound of the Mu Phone M 240

Mu Phone ad 1942
Mu Phone M419 element
M419 elemnt back