Support HammondWiki. Donate!

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.

A geometric series is a sequence of numbers where each term after the first is found by multiplying the previous number by a fixed number called the common ratio. In this case, the fixed number is the square root of 2 which is approximately 1.414124... So for each position on each drawbar, moving one number up connects that busbar to the next higher tap on the matching transformer, doubling the volume of that tone. Moving one number down halves the volume. Photographers might recognize the input turns follow the standard f-stop sequence (6 being the nearest whole number to f/5.6).

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

The content of this page is Copyright (C) 2000, 2001, 2002 Geoffrey T. Dairiki and the other authors of the content, whoever they may be.
This is free information and you are welcome redistribute it under certain conditions; see for details.
Absolutely no warrantee is made as to the correctness of the information on this page.