[sdiy] 303f - fix

[tomg@efm]

Two things if you are doing a DIY layout for the 303f....

1) I forgot to draw a 1K resistor from the base of the pnp
    transistor under the diode ladder to ground.
2) replace the 22K resistor on the emitter of the pnp 
    transistor used for the saw/(sorta)square converter with
    a 10K trimmer and 10K resistor.

Why #2? This transistor is very important for the 303 sound.
They must have selected each and every one. The truth is any
2n3906 (gen pnp) will work but you have to trim it for a uniform 
square wave. They were selected so the line never had to stop
to adjust it. You could sit down with a bag of 3906s, and find 
several that would work but we are just gonna trim it.

I used a "better" converter for the vco8-3046 do not be tempted
into replacing the 303 version with it. You'll screw up the sound.
I mean it! 

Crank the vco up to about 300KHz and adjust for the best 
square. At lower frequencies it really doesn't look much like
a square wave...sounds 303 though...it becomes a simi-sine
kinda round on the ends and flat on top....Nuff sed?...;-)

I wasn't going to trim the 303f because most beginners do not 
have scopes....but I decided that it can be done by ear reasonably 
well....Anyway there you go...part of the secret to the 303 sound....

Tom