[sdiy] A question about phasers/notch filters

[Ben Barwise]

On 7 October 2011 13:20, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
gue world, and may be difficult

> I'm not familiar with the device you mention, but these "infinitely rising"
> barber pole phasing things are usually achieved using a frequency shifter.  If
> you can frequency shift a signal using what the radio hams would call
> single-sideband supressed-carrier modulation, then you have effectively imparted
> a constantly increasing phase shift relative to the original signal.  If you add
> this frequency-shifted signal back to the original dry signal I think you get an
> infite series of notches that continuously rise or fall in frequency.
>
> Frequency shifting is different from musical pitch shifting and is usually
> achieved using a quadrature sinewave oscillator and a pair of ring-modulators
> (four-quadrant multipliers).  Since it shifts every spectral component in the
> signal by a fixed number of Hz it breaks the harmonic structure of musical
> notes.  For this reason it sounds quite discordant for large frequency shifts.
>
> I hope this helps,
>
> -Richie,


Just as a note , I cant help and I dont know if you have seen it Tom,
but heck out Jurgen Haible's Frequency Shifter, he talks about
baberpole phasing

http://www.jhaible.de/tonline_stuff/hj_fs.html
http://www.jhaible.de/fs1a/fs1a.html

-Ben