The instrument
The Hohner Symphonie 30 came onto the market in 1964 at about the same time as the Vox Continental and the Farfisa Compact. The sound is produced by oscillating tone generators. Philips in Holland built the Philicorda AG 7500 tube organ according to the same principle.
The Hohner Symphonic 30 has a range of 4 octaves and is equipped with a 16, 8 and 4 foot register. As different timbres it offers 2 in the 16`, 4 in the 8` and 2 timbres in the 4` range by rocker switch. The rocker switches have an additive effect on the overall volume. The red brilliant switch filters a strong mixture of overtones. The vibrato effect is selectable via rocker switches for tempo and tone strength. (Source: Werner Bothe)
Details
The sound is driven by a total of 12 oscillating tone generators that produce the frequencies of the tones of the top octave. A tone generator is an oscillating circuit and consists of a coil with copper windings and a capacitor as energy storage, which constantly interact with each other. A frequency divider circuit now divides the 12 frequencies in a ratio of 1 : 2 to the lower sounding octaves. The frequency division in the Hohner Symphonic 30 is done by an analogue circuit with glow lamps, which are supplied with a high voltage of 300 volts through the two tubes. Capacitors charge up and when the ignition voltage is reached at the glow lamp, it switches through. By charging and discharging the upstream capacitor, the sine wave of the oscillator is converted into a square wave with the same frequency. The sound of the Hohner is essentially characterised by the non-linear curve due to the glow lamp division. Germanium transistors were used for signal amplification.