[sdiy] Fatman module??

[Motohiko Takeda]

Hi! Tim and all!

I think there is so many kind of people. One wants to make music, and
the other loves electrical circuit design or only wants to build his 
owns.

Separating Analog synth in to parts, brings some benefit to the people
around this list.
Who want to design circuit, may consentrate to the circuit itself.
There is no need for pay attention to summing amps or something that
should to have to have.
It may reduce the time to develop. and make it easy to build. and also
make it easy to check their values or usefulness by the other builders.
And if there is a variations of them, the people have free to choose the 
controller and voice core each other.

Who can get small parts make it so small and smart. but who want to make
it easy to operation, need big knobs. Connect them each other then, 
dreaming things come true easily. 
And this project may easy to join for some kind of people.

Voice board has 3 address line. it will be numbered as follow.

1.VCO1 Tune
2.VCO2 Tune
3.VCO1 PWM
4.VCO2 PWM
5.MIXER balance
6.VCF Freq. cv
7.VCF Res. cv
8.VCA cv

and 1 cv line will multiplex or demultiplex by this address. We 
can do this easily by using 4051 with opamped buffer or something.
And for polyphonic project, We have 1 enable line. if this line off, 
this board can't get cv. if you are on Mono synth then this line 
should be on always. 
I recommend this discreet addressing system, not free run addressing 
with reset system.
This method will make easy to debug when we building voice core.

But now I wonder that there is some other need for the non CV 
line such as VCO sync or switching for sqr or saw wave form. 
I don't want to use 4051 or something for non CV line for their
cost. and I think that there is no need to use it.

At least, we need 4 VCA for CV controllable mixer, VCF res and 
usual VCA, and 1VCF and 2VCO.

And I should add one more story. This idea is originally coming 
from MR. tanaka who living in Japan. He is not only great builder 
but also a great amateur rank engineer. Mine is just a variation 
of his.

Cheers,
Motohiko Takeda
Tokyo Japan.