[sdiy] CS80 Filter IC schematic

[Roy J. Tellason]

On Monday 24 January 2005 10:18 am, Antti Huovilainen wrote:
> Hi
>
> Does anyone have schematic for the mystery IG00156 IC used in Yamaha CS-80
> filters? The chip has outputs named HP, BP, LP (and other pins) so I'm
> guessing it is some variant of SVF.

As it happens,  I do have a "datasheet" of sorts on this chip.  Says it was 
made by Mitsubishi,  though they don't give an OEM part number.  Says it's a 
VCF...

Pinouts are as follows:

1   AI   Signal input
2   KV   Key voltage input
3   fc   Adjustment of the cut off frequency
4   Vf   Input of the cut off voltage
5   Vcc   +15V DC voltage supply
6   Qo   Qo adjustment
7   VQ   Voltage input of Qo control
8   GND   Ground
9   FB   Q feed back
10  LP   Low-pass output
11  C2   Capacitor2 (fc determination)
12  Vee -15V DC voltage supply
13  BP   Band-pass output
14  C1   Capacitor-1 (fc determination)
15  HP   Hi-pass output
16  FBIN   Input of feed Dack (!)

>From what I can see in the block diagram,  the circuit is three amplifiers 
with two "Variable gm circuits" in between,  and two other blocks labeled 
"Cutoff control" and "Q control".  There's a bit more in another diagram 
labeled "Circuit Illustration" that doesn't really show all that much...

Hope this helps,  some.