Marconi-Reisz Carbon Microphone (circa 1930) Just the job for a Kings Speech or two! Also very popular with other personalities of 1930’s European showbiz!

Using this microphone requires the wearing of a dinner jacket and a black bow tie! (or a Fascist military uniform!)  Designed by the young George Neumann, working for Eugen Reisz, before he saw sense, and went on to make condensers! It is carved out of a solid octagonal block of marble, and filled with carbon granules (coal dust) behind a mica diaphragm.     (Short sound clip.)

Marconi Reisz showing screw holes to top up the carbon granules.

View inside Marconi Reisz Microphone

View inside my Marconi-Riesz with the front cover and wind screen removed. The thin mica diaphragm is glued on to the marble and the chamber containing the carbon granules is clearly visible. The screw holes in the marble have neat little fibre rawl plugs to hold the screws tight.

A great look for a mad Italian dictator!
Eh!… Benito I’m likin’ da mics!

Here is the original Reisz Patent from June 1925

Below is a simple circuit diagram for a pre-amp to power carbon microphones

Carbon Mic Preamp for Blog

CLICK HERE For new sound clip using this pre-amp.

Also an interesting technical article.

6 responses to “Marconi-Reisz Carbon Microphone (circa 1930) Just the job for a Kings Speech or two! Also very popular with other personalities of 1930’s European showbiz!

  1. Pingback: THE VIKING, EXTINCT AUDIO’S BM9 RIBBON MICROPHONE 2018. | Martin Mitchell's Microphones

  2. I wonder how effective just connecting it across a T-power input would be? After all, carbon microphones functioned with 50V in the telephone system – which given a local loop resistance of 50mA, so the 60-ish mA and 12V of T-power should be safe.

    Input impedance would be wrong, but possibly worth a try?

    Also for what it’s worth those rawl inserts are probably asbestos.


    • Hi Douglas, That is an interesting thought. I don’t think that 12v would cause a problem. Yes, might be worth a try. Though it may not sound any better ! Unfortunately I don’t have a source of T-Power at the moment but I have a colleague who might. I’ll investigate.
      And yes, the rawl plugs are probably asbestos. They came in a range of thicknesses and lengths and could be cut to size. When I was a kid my Dad still had loads of them in boxes in the garage! Anyhow, thanks for your comment.


  3. Hello,
    I own a similar model since many years and finally decided a try if it might work. I used an even more simple circuit and got this result:
    My very best wishes


  4. Pingback: Du fun avec des microphones : Neumann - DEVENIR INGESON

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