Moog HP #1b

[tomg]

> Hello Tom,
> 
> The wav sample of your new version HP sounds much improved.  The demo
sequence
> cracked me up - I liked the weird accidental countermelody that the
harmonics
> were playing (in part 2) while you swept the cutoff.  
> 
> The resonance oscillation section sounded kind of distorted, not very
sine-
> like.  Is that how the filter sounds, or is your bench amp adding some
"funk"
> to the mix?

It's the bench amp more than anything else. Don't you just love that
aluminum panel rumble....;-)
> 
> I wonder if it's possible to increase the upper frequency range of the
filter
> without sacrificing its lower range?  Maybe using a slightly higher value
for
> the caps? 

I started using a 0.1 this gives a higher range but you are correct in 
assuming the lower range suffers. 

> It'd be nice if it could climb right up into the squeakiest
> harmonic ranges, kind of like the MS-20 filter does - great for nasally,
> annoying, squelchy stuff. 

I don't think it ever will. It's much less overpowering.

> I notice that the original Moog HP had a 3-position
> switch for setting the overall frequency range of the filter.  It
switches in
> three different sets of caps with a 4p3t switch.  I hope this kind of
arcane
> arrangement isn't really necessary.

If you were going to build one for real I would say yes. I think a 0.1 and
0.22 switched would be enough though.
 
> Anyway, I'm having difficulty with my email right now, and I am not
currently
> able to download file attachments.  If you have the time, would it be
possible
> for you to post the new circuit schematic at your website? 
(moog_hp1b.gif)
> Inexplicably, I am able to download files from the web without problems. 
 I
> think my Melissa virus has a Y2K bug or something.  Or maybe it doesn't,
but
> needs one.

Sure it's there now. Enjoy

-tg