In a Hammond, the "chorus" effect is generated by mixing the "vibrato" signal with the straight or "dry" signal. The amount of ''vibrato'' signal included in the mixture is referred to as the chorus ''depth''.
-In a stock Hammond, the chorus depth is set by a fixed resistor (R44 in an [AO-28] organ). (The lower the resistance, the greater the depth of chorus.) It is interesting to note that different organs use different values for the chorus depth resistor --- in particular
, A-100's typically
have deeper chorus than B-3's
.
+In a stock Hammond, the chorus depth is set by a fixed resistor (R44 in an [AO-28] organ). (The lower the resistance, the greater the depth of chorus.) It is interesting to note that different organs use different values for the chorus depth resistor --- instruments built after the December 1957 vibrato system redesign have a metal linebox and the 12K chorus mix resistor rather than the 22K mix resistor found
in the earlier wood-linebox organs. Confusion results often due to the fact that the B-3/C-3 service manual never incorporated this design change. For example
, it is sometimes assumed that
A-100's have deeper chorus than the
B-3/C-3. Actually they indeed have deeper chorus than the earlier wood-linebox organs, but this is a matter of vintage, not model per se. The A-100 has the metal linebox and 12K mix resistor because it inherited the post-1957 design change having been introduced in 1959. Any console or spinet with the small metal open-frame vibrato linebox will have a 12K chorus mix resistor as built
.
A common modification is to replace or augment the chorus depth resistor with a potentiometer so that the chorus depth may be varied.
The following write-up on the modification was written by BradBaker. (This write-up describes a ''fixed'' chorus modification, but the ''variable'' chorus modification follows an obvious extension of this procedure.)
