The Formant VCF (Was: What is the data of this zener?)

Stefan Nielsen 932674 at
Fri Aug 2 18:44:45 CEST 1996

> In message <199608012128.OAA00152 at redshirt.tholian.web> you write:
> > >I'm building the moog ladder-filter found on, and on 
> > >the scematic there is this little annoyance. It's a small zener 
> > >diode, but I dont know the voltage and wattage of this thing. The 
> > >type number is LM329.
> > >
> > >Is there anybody out there who knows the stats for this?
> > 
> > Go to and do a search on
> > LM329.  In case you can't, it's a fancy 6.9V reference with up to 15ma
> > current handling.  I think somebody here mentioned a while back that a
> > 6.9V zener would work nearly as well, it's just that National
> > Semiconductor was trying to encourage use of their more expensive
> > product.
> I'm the originator of that Moog VCF circuit, be sure to fetch the 
> latest schematic from my web page, th eone on is outdated.
> If you're interested there's also a PCB available.
> LM329 is not a regular zener, it's a chip that behaves like a zener
> and delivers a voltage that is not influenced by temperature changes.
> You need it to set the temperature precisely, independent of ambient
> air temperature. For a filter I'd recommend leaving out the heater,
> I added it as a "plus".
> Rick Jansen
> __
> rick at

I went to your homepage, and it is *really* interesting. (Everybody on 
DIY - check it out, guys!)

I have a couple of questions to you, regarding the filter:

    * Is it your own design? If it is, do you know any good books
      about designing dynamic filters? I am myself 1 semester away
      from becoming an electronics engineer, and I have never seen
      this approach before. It is very clever.
    * What program did you use for the schematic? I usually use
      ORCAD (Argh!) or simply draw them by hand, but your method
      is *way* prettier!
    * What program did you use for the PCB layout? I made a PCB
      using Protel Easytrax, but that was downright awful. Plus
      the result is so full of errors that it made wire-wrapping
      seem a tempting alternative. No, forget that - wirewrapping
      is never tempting... :)

Have a nice weekend!

-------- URL: --------
------------- E-mail: 932674 at --------------

More information about the Synth-diy mailing list