[sdiy] AN299 and all that !

Tim Ressel madhun2001 at yahoo.com
Tue Jun 11 21:57:23 CEST 2002


Yo Pete,

I prefer the MAT04, because I'm addicted to precision.
The drawback is the MAT04 Ic max is 30mA versus 50mA
for the CA3046. So some twittling of the current limit
circuit is needed, and the temp range is limited
compared to the CA3046. I think its a good trade-off.

In this group you'll find advocates for all three
methods: An299, tempco R, and Jim's elecronic method.
All have pluses and minuses. Its a matter of style and
preference. One thing is for sure: whichever methode
you choose, these guys will help any way they can!

--TR


--- Jim Patchell <patchell at silcom.com> wrote:
>     Hi Pete...
> 
>     As far as the best way to go for expo
> converters, that is a matter of taste,
> somewhat.
> 
>     The CA3046 is by far the least expensive chip to
> make an expo converter out
> of.  I have had good results with it.  The MAT04
> will give you premium results
> at a premium price.  I have used it as well.
> 
>     As far as heat vs. tempco resistor?  I prefer
> neither.
> 
>     I am using an electronic scheme at the moment
> with good results.  The latest
> one I did is located on page 10 of this schematic:
> 
> http://www.silcom.com/~patchell/seqproj/1001013.pdf
> 
>     Don't confuse this with the temp compensation
> scheme that Paia uses on their
> 9720 VCO, which also uses an LM13700.  Of course,
> that is another option (a
> circuit diagram can also be located in the National
> Semiconductor data sheet for
> the LM13700).  In my scheme, I use the temperature
> of the expo pair to adjust
> the gain of a simple two quadrant multiplier (made
> from both halves of an
> LM13700).
> 
>     -Jim
> 
> 
> "Pete G." wrote:
> 
> > Hi Guys,
> > new subscriber here ! - just re-kindling my
> interests in building a Modular
> > - which began over twenty years ago - but which
> still haven't come to
> > fruition ..!. Maybe this time. Anyone remember a
> Babani book of sysnthesiser
> > projects from about 20 years ago by a certain M.K
> Berry ? (thats why my
> > stuff got shelved !!)
> >
> > I'm fairly new to the Web DIY synth resources -
> there does seem to be some
> > really excellent material out there, which is
> great news in a world where
> > analogue design is ever more marginalised.
> >
> > At my last attempt , I knocked up something based
> on the Nat Semi AN299 VCO
> > - had a lot of trouble with the integrator reset
> circuit ( that 'SCR'-like
> > thing). Did anyone ever get that to work reliably
> ? Got a few ideas of my
> > own I'll be trying soon.
> >
> > Whats best ?  - heated CA3046 / heated MAT04 /
> LM394 or SSM with Q81 ??
> >
> > Pete.
> >
> >
>
_________________________________________________________________
> > Chat with friends online, try MSN Messenger:
> http://messenger.msn.com
> 


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