An Electro/Hydraulic Amplifier

Gallery opened 26 July 2018

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This is a probably unique electro/hydraulic amplifier, in the sense that you put an electrical signal in, and get an electrical signal out, but at least some of the process of amplification is performed by hydraulics. It is based on the Vanni hydraulic microphone.

Left: Amplifier based on the Vanni hydraulic microphone: 1909?

H is a standard carbon microphone. The electrical signal from it, produced by modulating the current from the battery, passes through a transformer marked P S and applied to the coils E-E, which vibrate the diaphragm M. This process is purely electrical.

This movement is communicated to the pillar N and the lever L, so that electrode A is wiggled about, modulating the resistance of the acidulated water stream between A and B and giving a variable impedance to ground. The pointy thing at the top is the aerial, and the coil in the connection to it is the secondary coil of an arc or Fessenden continuous-wave transmitter.

I do not have high hopes for the audio performance of this arrangement. Whoever drew it seems to have misunderstood the principle of operation; the liquid column is shown breaking up into separate droplets that would surely have created a horrendous noise far greater than the audio signal.

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