Wiardgroup

There is a trimpot in the top center of the PCB labeled "Peak Q". This controls how much 
the Q gain is backed off with increasing frequency. You can turn it off, to eliminate the 
constant Q "feature".

For filters with Red LEDs, you can patch constant Q. Assuming an Envelator "O +"(positive 
envelope) output is driving one of the filter frequency control inputs, patch the "O 
-" (negative envelope) to the QMOD input. The setting of the QMOD attenuator then 
controls Q backoff with increasing frequency.

With a lot of Q backoff, the filter goes to zero Q at high frequencies, a complete reversal of 
normal behavior.

--- In wiardgroup@yahoogroups.com, "waveform100" <googol@g...> wrote:
> Yes, Constant Q is something to think about. I have one early Omni-
> Filter without constant Q and one newer Omni, with Constant Q (and 
> Blue LED's). Of course, a constant Q Filter is somehow easier to live 
> with, but I don't want to miss my older Omni. In fact the sound of my 
> older Omni is slightly different from the newer one and its not only 
> the Q-behaviour. Its really hard to describe.
> 
> The voltage controlled Filter-Mode is also hard to describe. Its 
> morphing not mixing and between the modes is really something going 
> on. Dramatic!
> 
> --- In wiardgroup@yahoogroups.com, "Gary Chang" <gchang@c...> wrote:
> > I have to agree with Olivier - the Omni is quite a useful filter - I
> > have a first generation "The Filter" and the last version of "The
> > Super Omni" - after several months of use, it became obvious that 
> the
> > Super was quite a performer, with many features, such as an 
> adjustable
> > "constant Q' circuit, which was designed to control the issue of the
> > filter being more susceptible to oscillatiion at higher frequencies
> > was also noticably quieter.  It is the fastest of the Wiard filters
> > (the Boogie being the next fastest, followed by the Borg).  The
> > bandpass is quite narrow, so Grant has changed the input resistors 
> to
> > provide a bit of input gain to compensated for lower output of the
> > bandpass.  What I like about the Omni is how hifi it is - then you 
> can
> >  drive the input a bit and get whatever amount of grnnge you want.
> > 
> > As Oliver described in his note, the MXR-type phasing produced by 
> the
> > notch is great - the direct input can be summed to the output, and 
> the
> > ouput of the filter has a phase switch, so there is plenty of 
> control
> > to make the filter sound good.
> > 
> > Though Grant has moved on from this design to his voctrol-based
> > designs, I would feel that something would be missing without the
> > Omni.  It is the Wiard Filter that can make great articulate bass
> > patches; while being less "phat" than the Boogie, it's speed makes 
> it
> > a great filter for many bass applications.
> > 
> > gary