Re: [linux-audio-dev] LFO Phaser LADSPA plugin in details

Hi, Fons!

======= On Monday 12 March 2007, you wrote: =======
> On Mon, Mar 12, 2007 at 12:53:28AM +0300, Andrew Gaydenko wrote:
>
> > Will anybody find a minute ot two to explain me how does the plugin
> > work - I mean a user POV rather technical realization details.
>
> (Assuming you mean my plugin from the MCP package)
>
> This is an emulation of an analog phase delay line phaser.
>
> "Input gain (dB)" Just what is says it is...
>
> "Sections", The number (1..30) of first-order allpass filters that
> form the delay line. The phase shift of each section is zero at LF
> and goes up to 180 degrees at HF.
>
> "Frequency", (in octaves) the frequency at which each filter section
> produces 90 degrees phase shift. The range is 12 octaves. Halfway
> is middle C.
>
> "LFO frequency (Hz)" Frequency of the LFO that modulates the "Frequency"
> parameter above (0.01 to 30 Hz).
>
> "LFO waveform". Sets the waveform of the LFO, from falling saw, over
> triangle, to rising saw.
>
> "Modulation gain", The amount of modulation by the LFO output.
>
> "Feedback gain". The gain (-1..1) of the feedback from the delay
> line output back to the input.
>
> "Output mix". The first half crossfades between the inverted delay
> output and the input, the second half between input and the normal
> delay output. Mid position is input, i.e. no effect.
>
>
> So if you set "Sections" to N, the phase shift in the delay line will
> vary between 0 at LF and N/2 cycles at HF. The "Frequency" setting will
> determine the shape of the phase curve and consequently the set of N/2
> frequencies where the delay output is in antiphase with the input.
> Setting "Output mix" to +0.5 will produce nulls at these frequencies.
> Setting it to -0.5 will produce maxima at these frequencies. "Feedback"
> will modify the effect in complicated ways. Finally the LFO makes the
> set of frequencies move up and down, producing the phasing effect.
>

Thanks! I'll play with the plugin having your words in front of me :-)
(have you found a chance to look at the qloud?)

Andrew
Received on Mon Mar 12 04:15:02 2007