Phase Shifter Staging

Discussion in 'Effects, Pedals, Strings & Things' started by dmczern, Jul 24, 2006.


  1. dmczern

    dmczern Member

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    Hello All,

    Could someone please explain this concept to me ?? I've done a number of searches and have not been able to find a good explanation for ME.
    What does it mean to have a 4 stage, 6 stage, or 12 stage phaser and how does it apply to guitar effect pedals as I haven't seen those terms in advertisements for phase shifters. Phasers I'm considering:

    Red Witch Deluxe Moon Phaser
    Moogerfooger
    HBE Psilocybe
    EH Small Stone

    I'm really mainly interested in the phase shifter aspect, as I already have a great vibe and tremolo.

    Thanks Everyone !
     
  2. Scrutinizer

    Scrutinizer Member

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  3. dmczern

    dmczern Member

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    Thanks Dave !!! I missed this one,
    will read as soon as "the man" gets off
    my back !!
    :JAM
     
  4. shakti

    shakti Member

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    I would highly recommend adding the Maxon PH350 to your shortlist. I prefered it over the Moogerfooger. *Very* lush, watery phaser sound, *very* vintage 70s Mutron-style sound. I think it's due to the photocells used or something (Non-Digital Tom can probably elaborate). It also has 4, 6 or 10 stages selectable, as well as variable feedback, so you can get anything from very subtle sweeps to wacked out self oscillation. The Moogerfooger has some zany sounds and extremely slow sweeps that are cool, but I don't think the base sound is as good. The bypass on the Moogerfooger also leaves something to be desired, IMO. The Maxon isn't true bypass, but has an excellent buffered bypass.

    I don't have any experience with the other ones on your list.
     
  5. Boogie92801

    Boogie92801 Member

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    I bought a psilocybe this weekend. Killer pedal. Much good tones to be had and covers most of the vintage sounds as well as getting pretty extream.
     
  6. dmczern

    dmczern Member

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    Shakti,
    Thanks for the reminder re the Maxon. I kind of blocked it out of my brain since I bought a Whirligig for the rotary thing. I revisited some of the sound samples and it certainly has the sounds/tones I'm looking for. I also dig on it's stereo output, that could be a lot of fun.

    Have you played through the Red Witch ??

    Thanks everyone for your opinions, this forum is so kick-@*& I can't believe it. Cheers Everyone :BEER !!!
     
  7. Cusack Effects

    Cusack Effects Member

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    Does anybody know why phasers always have an even number of stages? Is there any reason it can't have 3, or 5, or 7? I know the answer, just wondering if anybody else does?

    Jon
     
  8. brian marshall

    brian marshall Member

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    essentially a phaser is a notch filter that uses two equal phase shifts in a row... the phase shifts cancels out the mid frequencies.

    works like this

    .......................stage one..................stage two
    dry......................+...............................+......= +
    phased freq...........-...............................-.......= +

    you see the negatives cancel out each other, and go back to positive... but neg and pos are a misnomer because they are not actually 180degrees out of phase in two stages, and even when back to positive its still out of phase, but if you have a one stage phaser it ends up canceling everything either above or below the frequency center and it sounds like a tremolo... kinda
     
  9. Ed Rembold

    Ed Rembold Member

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    stated most simply......

    Every 2 stages produces 1 notch,

    2 stage phaser (Phase 45) has 1 notch
    4 stage phaser (P90, univibe) has 2 notches
    6 stage phaser (P100, small stone) has 3 notches
    The LFO "sweeps" the notches through the audio range.

    When you have 6 or more stages, especially when adding alot of feedback, your phaser begins to sound like a flanger.

    hope this helps,
    Ed R.
     
  10. Cusack Effects

    Cusack Effects Member

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    A single stage will also create a notch, which is what everyone seems to forget. The difference, and why it isn't done, is that the odd numered stages are out of phase, and when mixed with the original wouldn't sound right, so you would have to run it through a inverting stage before mixing it. Since you would need an Op-Amp stage for the inverting, why not make in another phase stage? I believe that is the only reason for not having an odd number of stages.
     
  11. tocs100

    tocs100 Member

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    Slightly OT, but does anyone have/know of diagrams showing what phasers do to a waveform? It'd be nice to show to non-musicians who want to know what modulation pedals do from a technical perspective.;)
     
  12. brian marshall

    brian marshall Member

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    ive looked at it on a scope before. its easiest to see with a straight up square wave. unfortunately all of my attempts to take pictues of the CRT with my digital camera have turned out really bad.

    if i get bored today maybe ill try it.
     
  13. tocs100

    tocs100 Member

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    Thanks Brian; that'd be great.
     
  14. dmczern

    dmczern Member

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    Quote:
    Originally Posted by brian marshall
    ive looked at it on a scope before....if i get bored today maybe ill try it.

    Thanks Brian; that'd be great.
    __________________

    Yeah, thanks Brian and thanks to everyone that's contributed
    to this thread. You guys are awesome!

    Cheers !!!
     
  15. gez

    gez Member

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  16. tocs100

    tocs100 Member

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    Cool! Could you also post a link to the article called "Digital Phase Shifting"? (My computer won't open any of the articles on the site's homepage, or download the illustrations.)
     
  17. Don Rusk

    Don Rusk Gold Supporting Member

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    well doesnt phase shifting itself involve one thing being 'out of phase' with another - or the relationship between two things?

    like you only get phase cancellations when using more than one amp or speaker etc --- the phase of a single object doesnt matter until it is confronted by another similar object.... sort of like magnetism ~~~ and voodoo :YinYang
     
  18. gez

    gez Member

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    http://www.beitec.com/digphas.htm

    The original article I linked to explains phase/phasers very well (especially if you refer to the diagrams), but will probably take a few read throughs if you're new to some of the concepts.
     
  19. cliffc8488

    cliffc8488 Member

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    Phasers don't *have* to have an even number of stages but in practical use they do. Each stage can contribute up to 180 degrees of phase shift (at infinite frequency). At the frequencies of interest each stage is designed to provide about 90 degrees. Therefore you need at least twio stages to get the requisite 180 degrees of phase shift. The phase-shifted signal is then added to the input signal and cancellation occurs at this frequency causing a notch in the frequency response.

    To get another notch you need to have at least 180 + 360 = 540 degrees of phase shift. Since each stage provides up to 180 degrees you need at least four stages to get 540 degrees at frequencies other than inifinity. The "classic" phasers use four stages to produce two notches. It is speculated that this was done to simulate the high and low rotor of a leslie cabinet.

    You *could* make a phaser with 5, 7, 9 etc. stages but it wouldn't provide any advantage over one with an even number of stages (4, 6, 8 respectively).

    CC
     
  20. fuzzyguitars

    fuzzyguitars Supporting Member

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    1+:rotflmao
     

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