Hammond XK-3C, Owner'S Manual

Page: 77 / 126

Setting the Parameters
77
Fundamental diagram of VIBRATO equipment
VIBRATO AND CHORUS OF HAMMOND
ORGANS
On string instruments, the vibrato effect is created by changing the string tension by ones
fingers. On wind instruments, by changing the strength of breath. On electronic instruments
with analog circuitry, by modulating the oscillator. As the rotation of the tone-wheels of the
B-3/C-3 is stablized by the synchronous motor, you can not obtain the oscillation accompa-
nied by a vibrato effect. So on these models, the vibrato effect is obtained by modulating the
tonal signal having passed through the drawbars.
The vibrato & chorus system of the B-3/C-3 consists of a phase-delaying circuit by plural
coils and a part called “scanner”.
When a tonal signal is passed through a coil, the phase delays. If plural coils are connected in
tandem and taking the output out of each tap from the top to the last by turns, the sounds
which pitches gradually lower are obtained. By taking the output out of eack tap from the last
to the top by turns on the contrary, the sounds which pitch gradually rise are obtained. These
operations are automatically made by turning the scanner by the motor.
The scanner is a part used to select one of multiple input terminals by the static connection.
As each terminal is selected by the “blades” which approach each other, a popping noise like
that of a switch does not occur and the signals of neighboring terminals cross-fade and switch
themselves.
The mode-selection of vibrato effects is made by changing the range of the connecting tap.
As this system modulates the produced tonal signals and not the oscillator, you can take out
the original sound without vibrato effect. By mixing the sound with the vibrato effect and the
original sound, the chorus effect is obtained.
On this model, these operations are simulated by the DSP.