Here concept MIDI-in of the device for Hammond is presented.

Principle of work following:

Each key is replaced with nine analog keys, instead of contacts. Certainly, it is possible to be connected to contacts directly, but it is very difficult for realizing technically. It is easier to use additional resistors. Moreover, there is an opportunity to change tapering and foldback (1 +) optionally, adjusting sounding of organ. There was an opportunity to use MIDI-keyboard with 60 keys on spinet models (2 +)! 5 absent tones can be partially compensated by foldback. But there are still more advantages. Details further.

Fig 1 sets an example of connections for one note. Each note has 9 analog keys (4016 or FET) which are controlled simultaneously by the MIDI-controller (MIDI-decoder) signal, 9 resistors and wires for connections according to the table foldback, or to your own choice.

It is possible to nominate initial values of all resistors 100 ohm (** fig 1), and  you can  reduce up to 50, 34, 24, 15, 10 ohm. by connecting the parallel resistor.

Values of resistors can be changed by connecting of other parallel resistor. This is very important feature since now you can easily change sounding of the organ (3 +).

Besides this principle gives an opportunity to add new drawbars (4 +), i.e. new harmonics (* fig 1). By the way, it is possible to involve non-used drawbars from pedalboards, and to create, for example, quart-intervals in the low and high register. On Fig 1 the probable variant of it is shown. You can even make up to 18 drawbars (2*9) for one manual!

The MIDI-controller also forms up a signal for controlling percussion (one touch). The mode of forming a signal by each pressing a new key, with other pressed, (every touch - trig) is also provided.

As for me, the absence of the click-effect is the serious lack (1-). But it is possible to achieve by simulation of a tinkling sound, and with adjustment of amount.

On Fig2 the possible kind of the switchboard is shown.

I tested the given concept in the form of experiment for several notes. I‘ve used TG (M3 model), drawbars and matching transformer. BTW, MIDI-in – is a good variant for construction of portable models (5 +).

Igor D.

november 2006

email: choplab@yandex.ru