Re: [AH] Re: VC EQ (was Cwejman Modular ...)

From Kenneth Elhardt
Sent Sat, Apr 8th 2006, 02:10

It's going to be a mess if I try to cut and paste from a bunch of different
posts.  I'll just try to clear some things up.

While many people don't always think of EQ as a synth module type, they
should.  I use EQ a large percentage of time in my sounds.  Those who bought
my first motm patchbook saw that.  Afterall, part of synthesizing a sound is
that you want to shape it or correct it into sounding the way you want it
to.  That's what subtractive synthesis is about.  Even looking at W. Carlos'
patches in the Box Set shows EQ settings.

Many modular synths have EQ modules.  Polyfusion had both 5 band parametric
EQ and 3 band formant filter (parallel bandpass filters) modules.  Modcan's
filterbank module is really EQ with +16db boost and about -48db of cut (or
something near that).  Modcan also has a single one band parametric EQ
module IIRC.  Roland System 700 had a graphic EQ module.  They're out there.

Q equals resonance on a bandpass filter and Q equals bandwidth on an EQ.
But that's pretty much the same thing because the more Q (resonance) you
have on a bandpass filter the thinner its bandwidth becomes.  Whether the
filter as a side effect or by design might also get louder when Q is
adjusted isn't really relevant.  Some filters do and some don't.  On an EQ
you have seperate control over cut/boost totally unrelated to Q/bandwidth.

It's kind of possible to use a parallel bandpass filter bank like an EQ by
mixing it with the dry signal as mentioned here and in the Doepfer manual.
You will however get a pretty strange filter shape when trying to cut freqs
because the bands don't flip upside down like in an EQ.  However as I have
pointed out many times in the past, it's possible to turn an EQ into
something that acts like a parallel bandpass filter bank by mixing the EQ
signal with the inverted dry signal.  They cancel out when all boosts/cuts
are at zero.  Then by boosting a band it appears from complete silence to
whatever level you set it to just like a synth fixed filter bank does.

The thing is, it's often you have a sound that is already near what you want
it to be but not quite there.  EQ works much better at taking a sound you
don't want to mess up but instead correct into something you want than some
parallel bandpass filter bank will do.  EQ is necessary for the serious
synthesist.

-Elhardt