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

[Tim Goetze]

Steve Harris wrote:

>On Sun, Oct 27, 2002 at 12:23:28 +0200, Tim Goetze wrote:
>> that is great to hear! i can almost see the box glowing from
>> the heat when the valves are turned on. the iir 'convolver',
>> btw, suffers greatly when competing for the cache with other
>> plugins now (8-9% @ 64/44.1). think i'll try the floats again.
>> though the k6 really is cache-starved compared to modern cpus.
>
>Well ,the more CPU you have spar, the more tempting it is to un extra
>stages and the more cache starved it gets.

live and learn. i'm looking into a few other places right
now to see where more cycles can be spared. the alsa out
node looks like a good candidate (i'm driving only one of
the ten output channels but zeroing the remaining nine at
every pass). should turn on -O2 instead of -g for the host,
too. :)

>> >used for all the stages, I suspect a chebychev would be better for the
>> >output, it would also alow us to model different amps with the same code.

forgot to ask ... you mean emulate a 'preamp', filter and
apply a 'power amp' [and filter again] and a 'cabinet' 
stage i guess?

>> >We'd need to calculate the added harmonics from an amp though, maybe by
>> >putting a sin through and FFTing it.
>> 
>> i've uploaded yet another recording, line-sine-16.flac, which
>> contains the line out (left) and the sine that went in. seems
>> our total transfer function until that point needs more work.

btw, the sine was produced by the virus, not the computer. 
thus it is 'sample-accurate', the output at one point in time
directly relates to the sine at the same point.

>I'm sure it does. I've been playing with myb ass and an ecasound chain:
>ecasound -i /dev/dsp -o /dev/dsp -el:valve,1,1 -el:dcRemove -el:amp,4
>-el:valveRect,0.5,0.5 -el:sinusWavewrapper,2 -el:valve,1,1.5 -el:dcRemove
>-el:amp,-10
>
>It needs some filters and more work, but it sounds pretty good to me.

just tried it, indeed it does. what i like especially is that
it sounds quite 'juicy' like good distortion is supposed to.
the attack phase is slightly better than with my previous 
setup, though there's still some auto-wah. still with the 
mixer pre-eq though, it reads '-15 at 80 Hz' so my guess is
the band it attenuates is too low for this purpose. haven't
measured its roll-off yet.

>I'm having a problem than when the input is 0, the output is infinite. I'm
>not sure if its a result of the optimisations I did, or it it would do
>that anyway.

should be the optimization, i'm getting clean zero out for 
zero in with your last public release. 

i still remember the green skies a M$VC optimized POV 
binary produced, since that day i'm a bit skeptical about
compiler optimizations.

tim