[linux-audio-dev] [ann] unmatched - a LADSPA amp tone

[Tim Goetze]

Steve Harris wrote:

>Thanks for doing that, I haven't had the time. Can you produce a spectrum
>plot for the current s/w chain?

http://quitte.de/sine-spectrum.gif
http://quitte.de/straight-spectrum.gif

the first is generated by this chain:
  Sine (1046.5022612023945), # c'''
  Valve (.3, .7),
  HiPass (200),
  Inverter(),
  Rect (.5, .6),
  Inverter(),
  SineShaper (2.),
  Valve (.7, .8),
  HiPass (30),
the second is the same chain with the SineShaper left out.

>It would be more efficient to just calculate the corect chebyshev in
>realtime, the problem is that they have lienar CPU cost with the number of
>harmonics, 20 harmonics for example will be pretty expensive. As we are
>building on the existing harmonics generated by the valve sim though we
>shouldn't need that many.

there's one problem i see: if we employ a chebyshev, it is going
to create harmonics no matter what amplitude our incoming signal
is iiutc. this is unlike the real thing, which will produce a
different spectrum if one is playing softly, or with the volume 
control set low. (i'm fond of this effect because it allows me to
change the sound pretty drastically without having to walk over
to the amp.)

tim