[sdiy] Unrolling the OBX voice card

[Antonio Tuzzi]

Hi Steve!

Thanks for the infos... (I have the schems...)

> > e10 FRLS VCF ADSR release ?0 -> -5v
> > e9 FDCY VCF ADSR decay ?0 -> -5v
> > e8 FATK VCF ADSR attack ?0 -> -5v
>
> Yes, the attack, decay and release voltages are 0 to -5V (MINUS 5V) and the
> sustain voltages are 0 to +5V (PLUS 5V).

On the CEM3310 data sheet, the attack, decay and release input are
connected with a 10k resistor,  and there is a suggestion to use a 0v
to -5volts swing to go from 2ms to 20secs.

In the OBX , a lot of continuous value are set using pots traveling
between 0V and 5.6V, values are buffered with tl084. For the Attack
Decay and Release values, there is another stage of inverting and
scaling using LM324 (scale -(4.87k/100K)) and on the card there are 10
Ohm resistor connected to the A D R inputs of the CEM3310.
But I really was expectiong a 487 ohm resistor to have exactly the
same range as the one indicated in the CEM datasheet.
Any idea ? (i checked OBXA schematics and there is the same) Am I
overlooking something ?

Thanks
antonio