> > I read (a fairly scholarly) paper on modular synthesis
Oww.
I sprained my tweaky finger when I read this.
Hope you don't mind if I comp along in the background while you engineers go on
a bit.
[Hhreene breenay whooommple plink. Plakelee pladaa squeeedle deedle doodlee
oomple.]
[DC al Coda]
Ed Edwards
Leader: Ezekiel's Wheel »»»»Retro-Progressive Rock««««
http://www.ezekielswheel.comhttp://www.untiedmusic.com/ezekielhttp://www.headholemines.blogspot.com°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°
> -----Original Message-----
> From: AN1x-list@yahoogroups.com [mailto:AN1x-list@yahoogroups.com]On
> Behalf Of Dan
> Sent: Monday, April 18, 2005 5:10 PM
> To: AN1x-list@yahoogroups.com
> Subject: Re: [AN1x] Aliasing
>
>
>
>
for the
> Nord
> > Micro Modular and it said unequivocally that digital oscillators
> have
> > more energy above 10,000 Hz than their analog counterparts
> ============================
> Here's part of the article that I was referencing:
>
> http://www.cim.mcgill.ca/%7Eclark/nordmodularbook/nm_oscillator.html
>
> > "Rob Hordijk has developed a very nice sounding "analog" style
> filter. His filter avoids the "buzzy" sound produced by many digital
> resonant filters. The buzziness arises because digital oscillators
> contain a relatively large amount of energy above 10kHz. Most analog
> oscillators have less energy in this region, as the analog circuitry
> itself filters part of it away. Imagine a sawtooth set to 200 Hz,
> therefore having overtones 200 Hz apart from each other. This means
> that in the area between 10 kHz and 20 kHz there are 50 overtones
> present, all crowded together within a single octave! When using,
> for example, 3 slightly detuned oscillators you're talking about 3 ∗
> 50 = 150 overtones all in that one high octave, and all phasing fast
> with each other. The amplitudes of these overtones are very small,
> but there are a lot of them and very high sounds are perceived quite
> well, so there is a distinct buzz in the high. If the cutoff
> frequency is set to this area the buzziness is increased even more
> at high resonance levels. The resonance band of a 12 dB filter is a
> bit broader than that of a 24 dB filter, so the 12 dB filter suffers
> a bit more from the buzz.
>
> The problem with this buzz is that it can mess up those other sounds
> that have by nature lots of energy in the same band, notably hihats
> and cymbals and some dipthongs in the vocals. Thus it is a good
> practice to filter everything above 10kHz away from all instruments
> when there are hihats and cymbals in the rhythm track, or if you use
> vocals from someone with a clear voice. Otherwise these hihats and
> the s's and t's will drown in the high of the other instruments. Its
> even worse if the 10kHz+ area gets in a reverb with a very bright
> tail. That will start to produce lots of noise.
>
> For most synth sounds, especially strings, its not the 10kHz+ area
> which is important, but the area between 3.5kHz and 10 kHz. So
> filtering away all above 10kHz but slightly emphasizing the 3.5 to 8
> kHz area greatly improves the warmth and depth of stringsounds. A
> single 6 dB LP filter set to 10kHz won't do the job, the cutoff
> frequency should be set to 2.5 kHz or less to effectively remove the
> buzz. Even the cutoff frequency of a 24 dB filter should be set to
> something like 5kHz. But in both cases you would also lose part of
> the important 3.5 to 8 kHz area. The most useful solution is to use
> a dipfilter with a notch around 12 kHz.
>
> The filter is composed of two 12 dB filters that are cascaded to get
> a 24 dB filter. On the first filter a little bit of the HP output is
> mixed to the LP output. This is tuned by a MasterOsc module. As it
> apparently needs some bizarre overexponential control to get
> everything right, the grey signal is raised to the power of two and
> mixed with the grey signal to control the amount of HP. This creates
> a notch at the top end of the spectrum, which does three things:
>
> 1) it attenuates the very high end, making the filter less "buzzy ".
> 2) it reduces the resonance at the top end of the spectrum relative
> to the rest of the spectrum, especially at high resonance settings.
> This also makes the sound less buzzy.
> 3) the notch increases the filter slope slightly.
>
> The messing about with that grey signal is just to keep the notch at
> the right place, which is tuned to taste by ear.
>
> The second 12dB filter increases the filter cutoff slope to 24 dB.
> The feedback from the LP output of the second filter increases the
> bottom end of the spectrum, giving the sound a little bit more guts.
>
> This filter can give good analog bass sounds with even a single
> sawtooth oscillator. "
>
>
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