On Fri, 17 Jul 2009 19:18:30 -0700 Ken Restivo <ken@xxxxxxxxxxx> wrote: > On Fri, Jul 17, 2009 at 05:43:09PM -0700, Justin Smith wrote: > > On Fri, Jul 17, 2009 at 4:47 PM, Ken Restivo<ken@xxxxxxxxxxx> wrote: > > > On Tue, Jul 14, 2009 at 04:13:13PM -0700, Justin Smith wrote: > > >> On Tue, Jul 14, 2009 at 3:56 PM, Fons > > >> Adriaensen<fons@xxxxxxxxxxxxxxx> wrote: > > >> > On Tue, Jul 14, 2009 at 03:25:39PM -0700, Justin Smith wrote: > > >> > > > >> >> Try running a white noise source through the filter, then > > >> >> look at the spectral graph output in your favorite spectrum > > >> >> analysis program. Since white noise should have a flat > > >> >> spectrum, any peaks and valleys in the output are those of > > >> >> the filter. > > >> > > > >> > For a more 'musical' analysis, use Japa. It has either > > >> > a logarithmic or perceptual frequency scale. Pink noise > > >> > source is built-in, and if you set the analyser response > > >> > to 'Proportional' it will show a flat spectrum for pink > > >> > noise. It can also show the difference between two spectra, > > >> > e.g. input and output of a filter, and this produces much > > >> > more stable displays when using a noise test signal. > > >> > > > >> > For the filter, you could try on of the four Moog VCF > > >> > plugins I wrote years ago. Apart from the resonant > > >> > lowpass they will also add some juicy distortion at > > >> > high levels, as does the original Moog filter and > > >> > probably all real analog Wah processors. Frequency > > >> > control is logarithmic, which is probably what you > > >> > want, and there are separate control inputs to > > >> > set the static frequency and resonance and their > > >> > modulation. One problem could be that the modulation > > >> > inputs require audio rate signals (the filter were > > >> > designed for use in AMS) but that can be changed > > >> > easily if you want. If you want to play with them > > >> > use AMS. > > >> > > > >> > But Japa and the filters to be found at > > >> > http://www.kokkinizita.net/linuxaudio/downloads > > >> > > > >> > The filter plugins are in the MCP set. > > >> > > > >> > -- > > >> > FA > > >> > > >> I used japa years ago, but forgot its name, thanks for this > > >> excellent piece of software, which I am excited to have > > >> rediscovered. > > > > > > > > > Mille grazie! I've got JAPA going on two platforms, but I've got > > > to apologise for being a bit dense in figuring out how to use it. > > > > > > The UI looks a bit like an HP oscope, but, alas, i'm not much of > > > an engineer, so I'm not sure to start. Is there a quick simple > > > tutorial somewhere on how to use it? Anyone care to give me a few > > > sentences of advice? > > > > > > I basically want to put white noise through some filters (prolly > > > using JACK-RACK), and view the frequency response of it. Looks > > > like JAPA already has a built-in white an pink noise generator, > > > which is nice. What would I connect to what (using i.e. using > > > jack_connect) and how would I set up the switches and control on > > > JAPA to do this? A simple screenshot of the correct setup might > > > be enough to get me going. > > > > > > Thanks again! > > > > > > -ken > > > > > > > Connect the pink output of japa to the input of the application with > > the filter, connect the output of the app with the filter back into > > japa, the curve you see in japa will be the frequency response of > > the filter. Since japa can overlap displays, you can also try > > putting some musical material through: one input straight into > > japa, one through the filter first, and look at the compared > > spectrums. > > > > Another possibility would be routing the japa pink output to an > > analog wah pedal, and comparing the frequency response of the > > analog pedal coming back in to the digital wah emulator. Or you > > could compare the spectral output of the real and digital wahs with > > musical input. > > > Thanks. > > I did as you suggested, and it worked! But I'm confused by the > results. > > This is straigtht pink noise directly from JAPA's generator back into > its input... but the frequency response appears not to be flat! > http://restivo.org/misc/pink.png Well, as Fons said, if you set the display to proportional you'll get a flat response with pink noise. > The white noise was similarly not flat: > http://restivo.org/misc/white.png White noise will be a straight line as well, but not flat > So, in terms of viewing the response of the filter, do I need to A/B > or A-B to get some kind of estimate of what the filter is doing? > > -ken Seems like there are a lot of things you can do, a lot of ways to handle that, storing in X or Y, etc. Regards, Philipp _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
