The Yamaha AN1x Synthesizer mailing list

> The LPF refers to the fact that most tube amps lose high end when they're
overdriven at the output stage.  The harder they're driven, the more the
high end rolls off.  This LPF is a fixed amount, unlike the VCF in the AN1x.
It helps to take the edge off the sound.  There is a balance that must be
struck between the VCA level of the patch, the Gain setting of the tube
simulation, and the LPF frequency to get the right tone.

Agreed --- now here's the hard part --- the LPF effect in a tube amp is
dynamic.  That means that at lower volumes the treble portion is let through
but at high volumes the "scoop" effect kicks in proportionally to the amount
of volume.  Most synths can't properly simulate this audio effect.

The LPF property of overdriven tube amps falls under the "happy accident"
theory.  Similar to Leo Fender's production of the Telecaster, which is sort
of a hard body banjo, therefore the twang sound... Fender was more
interested in profits than sound in his design but stumbled on a useful and
different musical instrument.  His happy accident was that he created a
sound which was previously difficult to produce.  The LPF property of a
Marshall or whatever amp which has been fed voltage beyond the design's
parameters is a happy accident.  The Marshall amps were designed to provide
"clean" guitar sounds.  Players found out about the overdrive through
experimentation.  Legend has it that when Eric Clapton played his overdriven
Marshall sound in the studio the engineer was very angry and said that the
sound was bad, and said that nobody would listen to his record.  Sorry Mr.
Engineer.  Maybe the "cabinet emulation" section of the AN1x might be able
to provide a similar filtering effect.

Ed Edwards
Leader: Ezekiel's Wheel      \ufffd\ufffd\ufffd\ufffdRetro-Progressive Rock\ufffd\ufffd\ufffd\ufffd
http://www.untiedmusic.com/ezekiel
http://artists.mp3s.com/artists/227/ezekiels_wheel.html
\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd\ufffd.\ufffd\ufffd