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.