[sdiy] cheapest DIY phaser. Was: band reject filter.

[tomg@efm]

Works to about 35V, 25-30V to be safe. Work on  the 340/320 pair.
Makes a simple dual regulated supply. Use a 5K pots and it's variable 
+/-5 to +/-25...

Tom
 


> Phasers are everywhere...
> >> I've noticed that using a band reject filter (I use negative gain on
> >> a parametric equalizer) and sweeping the frequency sounds a lot like
> >> a low resonance phaser.  Is this due to the negative interference of
> >> a phaser cutting out different frequencies as it comes in and out of
> >> phase?  How exactly does a phaser work, anyway?
> >>
> >> -Tavys
> >A phaser is one or more notch filters, that have there frequency swept up
> >and down by an LFO, so what you were doing is essentially making a very
> >crude phaser.
> >
> >Seb Carr
> 
> In a phaser, a delayed signal is added to the original.
> The delay is tiny, you usually want it less then a wavelength of the input.
> 
> While adding a delay over an original, you'll end up having a pattern
> of frequencies that are cancelled out, and added in.
> This happens, because a certain frequency might be delayed just so much
> that it appears to be the opposite of it's original. If this happens at -say-
> 300Hz, It will also happen at 600, 900, 1200, etc... if the phaser behaves
> according to the books.
> This is called a combfilter.  _/\/\/\/\/\/\
> 
> As the ear perceives patterns rather then actual frequencies, the
> 'distance' between the cancellations is audible as a tone.
> so if there's a 300Hz distance between each cancellation, you'll hear
> that tone, and not 600, 900, 1200, or higher.
> 
> But if the phasing is not to heavy, it will be perceived as something else.
> If someone is speaking to you at some distance from a wall, you'll hear the
> voice directly and reflected via the wall, which is thus delayed.
> And yes, here is a combfilter as well. But you do not perceive it as such,
> nor would you perceive it as a tone. Your brain reworks it into a spatial
> 3D image of a room with a soundsource in it, and -alas- doesn't lecture
> your concience with mathematical thoughts on combfilters.
> 
> But as soon as the speaking person starts moving about, you might hear
> the combs shifting, you might start hearing not only a moving soundsource
> in a space, but also the fenomena itself: combfilters, phasing.
> And if it happens real close, you'll notice the comb is a tone.
> 
> If you can't talk the speaking person into banging his head to the wall,
> you can also fix the distance of the speaker to your ears
> and move the reflecting wall at a close distance:
> Move your hand to and away from your mouth while you sing.
> If you'll do it slow, you'll hear your hand a moving. If you do
> it fast, you just made the cheapest DIY phaser.
> 
> 
> Dave Krooshof
> 
> 
> 
> 
> Ps.1
> Bigger hands phase better. You can use cd cases or books as
> hand extensions. Do it alone and switch off the webcam, people
> might think you're going mad.
> 
> 
> 
> 
> Ps.2
> Take care: You'll might start noticing that you can hear trees and
> streetlights as you pass them by the filtercharacteristics of their
> reflections. You can't tell anyone about it as people will think you're
> mad. (It all started when he began discussing his synth on the web)
> 
> 
> 
> 
> 
> 
> 
> 
> Ps.3
> "I'm not mad, I was f.i. never aware of moving combfilters while making love.
> Come to think of it, your voice must be phasing while at it. So this is why
> http://www.till.com/articles/moog/patents.html#US03800088 sounds so
> intimate"
> 
> 
> 
> 
> 
> 
> 
> 
> http://www.combfiltersociety.org/psycology-tragedies/freedavenow.html
> 
> 
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> 
> http://www.xs4all.nl/~krooshof
> 
>