hybrid synth (was: Looking for the right book ...)

[franck pissotte]

Duane R Balvage wrote:

> > My idea, since a CPU is needed for MIDI, is to build a simple hybrid synth,
> > with LM13700 for VCF and VCA and digital stuff for the rest.
> 
> An excellent idea... I am pursuing such a project myself. I was just
> looking at the ATMEL microcontrollers and the PIC microcontrollers for just

i also downloaded some datasheet for atmel, pic, scenix and few oldies
like 68HC11, ST6, 80C31.
pic and atmel are the cheapest for single chips, but if external RAM, EPROM 
is needed 80C31 seem a good choice, with lot of compatible chip with
extension
(one have 8 channels 10 bits A/D good for a vocoder)
choice is difficult, but one of my requirement is availability of free
DIY programming board with serial or parallel port on a PC.
8051 instructions and memory addressing is strange, risc instructions are 
more regular.

> (in fact, you could probably use the "real small" PIC controllers for
> DCO's one for each voice! They are definitely "cheap" enough...)

yes! several A/D converters in DIP8!
the ADSR in one chip! 4 pots on A/D input. output on PWM.
don't now if the PWM controlled output voltage will be useable.
i see applications notes on digital filtering with PIC.
may be a "PIC synth" could be build?

>    Incidentally, there are a lot better filters than the LM13700 type
>    Take a look at TomG's site... He's got almost every filter type known
>    to man.  http://www.mindspring.com/~vco/

i will take a look at this site (and lot of other) to select schematics.
LM13700 have an advance over other, since they are in my stock. 
for my first synth i don't need the best sounding but a very simple and
very cheap synth. i am sure i will find something.