[LAU] Frequency-response analyzer for Linux?

Justin Smith noisesmith at gmail.com
Tue Jul 14 19:13:13 EDT 2009

On Tue, Jul 14, 2009 at 3:56 PM, Fons Adriaensen<fons at kokkinizita.net> 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
> Io lo dico sempre: l'Italia è troppo stretta e lunga.
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I used japa years ago, but forgot its name, thanks for this excellent
piece of software, which I am excited to have rediscovered.

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