EMS filter construction

[Paul Maddox]

Blandon,


   I built this VCF... to be honest I wish I hadn't wasted the
time or money on it.. It sounded awefull.
I even did a PCB foil for it.. Check out my web page, in the 
back issues section.

   Anyway, I used a TL074.

  Paul

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-----Original Message-----
From:	Blandon Ray [SMTP:arp2813 at home.com]
Sent:	Wednesday, September 08, 1999 9:37 PM
To:	Synth DIY
Subject:	EMS filter construction

I originally sent this to AH, but at the suggestion of a listmember
I'm forwarding it here as well...



greetings all,

Now that I have been able to build several Paia kits with reasonable
success (most recently a Fatman, with which I am very pleased), I
want to increase my skills and tackle a true DIY project. For
starters I thought I would try to build this EMS filter, just as an
exercise:

The schematics can be found at music machines:
http://machines.hyperreal.org/manufacturers/EMS/schematics/emsfilt.gif

This specifies 741 opamps, but knowing the conventional wisdom on
that part I thought I'd try to use something better. I did check the
archives, but I found a wide variety of opinions on what to use as a
replacement, so I thought I'd seek some feedback on this particular
application. If I read the schematic right, IC1 and IC2 are buffers,
and IC3 is in the signal path as part of the Resonance circuit (I
don't know enough to look at these things and exactly tell their
function; that's partly why I want to try building this). Also there
are these BC109C transistors, which from what I've read seem to be
obsolete as well.

So if anyone has any recommendations on these issues (or in
general), I'd appreciate it.

blandon