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While Drawbars or Presets control the desired level of each harmonic, the matching transformer is where the harmonic levels are actually set and blended together. The drawbars or presets route the individual harmonics from the Busbars to one of nine input taps on the primary side of the matching transformer. The first tap is grounded and this shunts any harmonics from drawbars that are in the off position. From Hammond's original patent~:

    Taking into consideration Weber's law, the taps on the transformer...are respectively at
    6, 8, 11, 16, 22, 32, 45 and 64 turns.  This series of numbers consists of the nearest
    whole numbers to a geometrical series commencing with 6 and having the square root of 2
    as a ratio. Since voltage is proportional to the number of turns, and since the energy
    is proportional to the square of the number of turns, and it is the energy which determines
    the intensity of the tone...connecting a generator to a tap on the transformer one step
    higher than that to which it was previously connected, will result in substantially
    doubling the intensity of the tone produced.

See HammondPatents.

The patent further states that therre is a 477 to 1 turns ratio between the primary taps and the secondary. This lifts the voltage produced by the tone generators.

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