Date: Wed, 19 Feb 1997 11:43:05 +0100 To: Tom Verheyden From: Thomas Michaux Cc: synth-diy@horus.sara.nl, analogue@hyperreal.com Subject: BassDrum 606 sound-change Tom Verheyden wrote: > ... > FIG. 11: --------/\/\---------- > | R2 | > | | > |---||----+----||----| > | C1 > R1 C2 | > | < | > |--|\ v GND | > | \______________|____ Periodic wave out > | / > Pulse in ------|/ > > f = 1/(2pi*SQRT(R1*R2*C1*C2)) > > Q = SQRT(R2/R1)/(SQRT(C1/C2)+SQRT(C2/C1)) The BassDrum sound on the 606 is based on 2 bridged T-network filter like the above. I worked only on one of it made by the components : R59 (R2) = 680 Kohms R58 (R1) = 3.3 Kohms C20 (C1) = 56 nanoF C19 (C2) = 56 nanoF Which gives orignally : F=60 Hz Q=10 What I made is doublin the Q factor to have a longer decay, whitout modyfing the frequency F. You just have to double the value of R2 and divide the value of R1 by 2. Do do this I put a 680 Kohms resistor in serial with R59 and a 3.3 Kohms resistor in parallel with R58. So the new value after mods are : F=60 Hz Q=20 The decay seems to be longer but now the problem I got is evident : Q as increased so the sound level too, saturation comes faster. What I'm searching to do is a kind of feedback just like the one on the 808. Could someone help, anybody already tried to modify BD sound on the 606, related experiences welcome. Thanks. Thomas.