Can a diode/transistor ladder filter be run from a single-ended power supply?

[Sean Costello]

Hi everyone:

I want to actually start building some of the circuits I have on my page
(http://www.seanet.com/~costello), but I would like to make a few
changes.  Specifically, I would like to create a diode ladder filter (a
la the VCS3 or TB303) that can be run off of a single ended power supply
(in this case, a 9V battery).  I just like 9V batteries, OK?

Any ideas how I would go about this?  I know the TB-303 uses a single
ended power supply, so I know that it is possible.  The tricky part is
the transistor(s) that convert the filter voltage control into the
exponential current needed for the diode ladder.  I could just copy the
circuitry from the TB-303 (it is pretty darned nifty, with the "gimmick"
for lowering the cutoff frequency while increasing the envelope
modulation), but I would really like to know what I am doing before I
start.  I really don't want to simply clone the 303 filter; I'd like to
adapt the core of the VCS3 filter (check my page for a reasonable clone
of the VCS3 filter), and possibly use germanium diodes for the filter.

Any other issues I would encounter with running the VCS3 filter off of
+9V?  How about the diodes at the "top" of the ladder (i.e. the 3 pairs
above the main R/C diode pairs)?  What do they do?  

Also, could the TB-303 expo stage be used in a Moog ladder filter?  Can
the Moog ladder filter run off of a 9V battery?  The schematics for the
discrete Moog filters (Minimoog, 904a) seem to only use the negative
supply for the exponential convertor.  Can these be converted to run off
of a single ended supply?  Advantages, disadvantages?

Any advice welcome (answers, directions of where to look for answers,
etc.). 

I'm also interested in creating an MS-20 filter section clone that is
battery operated (I LOVE battery operated boxes - my little x0x boxes
are getting a lot of use nowadays, while I wait for the NM to arrive).
Any advice there?  It seems more straightforward - just using a voltage
divider to create a "virtual ground" that is 1/2 of the positive supply.
Any other tricks?

Thanks,

Sean Costello (who realizes how this post totally gives away his
ignorance of all things electronic.  I was reading "The Art of
Electronics" last night, and learned way too much that I should have
known before.  Apologies in advance for my ignorance, but I really do
want to learn this stuff.)