[sdiy] Rays modules ==8-O

[Tim Parkhurst]

> -----Original Message-----
> From: Tim Johnson [mailto:ifixaudio at hotmail.com]
> Sent: Friday, October 22, 2004 10:21 AM
> To: synthdiy at sdiy.org
> Subject: [sdiy] Rays modules ==8-O
> 
> Hello Group,
> I've decided to cut out some of Ray's modules on my board mill but the VCO
> skeers me.
> Can anyone provide me with the appropriate tempco?
> I don't want to hunt them down only to have to order a thousand of them.
> Also will I have a hard time find LM13600 I.C.'s?
> I was actually thinking of the simpler 4069 osc but it lacks the sync, PW
> and other features I would really like. Could they be implemented in the
> 4069?
> Is there a simpler osc that has these features only simpler to build? I am
> really not concerned about temp stability.
> Finally, would I be able to use rotary switches to "patch" them together?
> 
> (Oh my gosh, I need a Valium!)
> 
> Sorry for all the ?? and as always
> Thanks
> 
> Jim
> 

Hi Tim (or Jim),

As far as the tempco resistor, see the earlier post (just an hour or so ago)
by Jay. He's placing an order for 1K tempcos and is offering them for $2.40
each. Pretty good deal. 

As far as the ICs, I'm pretty sure you'll want the LM13700. These are
available from Digi-Key for $1.43 each and Mouser for $.72 each! Just make
sure you order the DIP or PDIP package (the other packages listed are
surface mount). 

As far as the complexity of the circuit, it's about as simple as it gets for
a 'full featured' VCO. This one has expo and linear CV inputs, Sync, PWM,
and all four 'classic' waveforms. Looks like you could leave off the
circuitry around the sine shaper if you don't need a sine wave, but since
the LM13700 is a dual OTA you already have that IC on the board anyway.

As far as the rotary switches, I don't see why not. Good quality rotaries
are expensive and kind of big (1" in diameter or more), but if you are okay
with those restrictions (or you can find some good surplus units), then I
think patching with the switches should work nicely. 



Tim (about as simple as it gets) Servo
 

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