Hi Martin,
Just coming in after Bruce's excellent overview, I'd just add a little
about resonance.
In theory, a filter's response can be drawn as a nice curve which
eliminates frequencies at a particular rate. So if it was linear it would
cut off signals at an arithmetic rate such as 12db or 24db per octave like
the AN1x emulates. But devices such as capacitors, resistors, coils,
circuit boards and other parameters do not have "theoretical
characteristics". Therefore, the developers of Virtual Analog emulators
(like the AN1x, Roland JP8xxx series the Ion and others) try to mimic the
quirks of old analog electronic hardware design inaccuracies.
Resonance as a synth parameter is usually at the frequency where the
filter starts to cut off the sound. So if you have your filter set to cut
off 1kHz, there is a little more passage of that particular frequency to the
output because of the imperfections of the circuitry. The synth designers
decided that this quirk may be a good thing and produced components and
knobs that emphasized that peak. Due to the way electronics behave, this
filter peak could be driven to the point that it produced a signal on its
own with no oscillator input. This is called self-resonance and can be
pretty cool (and can be dang over used as well). A great example of strong
filter cutoff and resonance is the reknown TB-303.
Anyway, enjoy your AN1x. It's design is still very much useful as a
musical instrument.
Ed Edwards
Leader: Ezekiel's Wheel »»»»Retro-Progressive Rock««««
http://www.untiedmusic.com/ezekielhttp://artists.mp3s.com/artists/227/ezekiels_wheel.html°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°·.·°