Designing multistage signal phasing.

Discussion in 'The Projects Forum' started by E.E., Apr 3, 2008.

  1. E.E.

    Thread Starter New Member

    Apr 2, 2008
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    Hey guys! Just a little backround, I am a student of E.E. working on some projects for my own learning experience. So I am building a circuit called a phasor for a guitarist buddy of mine. The idea is I have a buffer OP Amp(OP07 for low noise) that has its neg. feedback loop connected to 4 Dual OP Amps(8 stages in total). So my question is what kind of timing I should use. I need the signal to be 90 degrees out of phase. With the original signal passing through the buffer, would it be better to use a 555 timer to delay the signal or a 12 bit counter with an alternating reset voltage. Or any other ideas?
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    There is something called a bucket brigade that will delay a signal, but I don't remember much more than that. Both the alternatives you mention are digital, I don't see how they can work. Do you need 90 degrees across the specturm, or just for one frequency?
     
  3. E.E.

    Thread Starter New Member

    Apr 2, 2008
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    Crap, thats right it is digital. Yes the full spectrum 90 degree shift. Thanks for your input man!:)
     
  4. Wendy

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    Mar 24, 2008
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    I'm probably inserting foot at this point, but a 90 degree phase shift would be a different delay for each frequency. I'm not sure how you would accomplish that.

    An RC circuit would do it, but it is also a filter, which sounds pretty undesirable from here. There might be a way to equalize the signal after the shift though.

    The bucket brigade shifts (delays) an audio signal by a fixed number of milliseconds, which isn't quite it either.

    There is probably a way to do it, but I'm not the one to know how.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Check out this page:
    http://www.geofex.com/
    There's a phaser schematic, 2nd link down.

    (Dang, 2nd time today I've referenced that link) ;)
     
  6. E.E.

    Thread Starter New Member

    Apr 2, 2008
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    Hm, well I was thinking about this. I'm wondering if I can use a digital counter as a trigger instead of running the audio signal through it. So I would have a trigger voltage for each OP Amp, if you understand what I am saying.

    The shift does not have to be 90 degrees at all times, just no more than that. I guess I should of clarified.

    Hm, the RC would work, but I do agree with the filter.
     
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I think you need a Hilbert Transformer (Google). Unless you happen to stumble across someone with experience, I think you will have a tough time. I believe digital implementations (but not the ones you suggested) are simpler than analog.
     
  8. E.E.

    Thread Starter New Member

    Apr 2, 2008
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    I've actually referenced that circuit, but I cannot see how it works actually. The thing is, I want to trigger each of the OP Amps(like at the bottom of the schematic) with a slight(nano sec) delay so the signal is out of phase if you understand what I am saying. Thanks though.:)
     
  9. E.E.

    Thread Starter New Member

    Apr 2, 2008
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    Digital is not an issue for me actually. I just want to avoid D/A and A/D conversions for such a small circuit.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Actually, you could do the whole thing in an MPU; there are scads of them around with multichannel ADCs and DACs built right in.

    Your problem then would be reduced to what to do with all the leftover machine cycles. ;)
     
  11. E.E.

    Thread Starter New Member

    Apr 2, 2008
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    I'm sorry, like I said I am a student so what is an MPU?
     
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