Adjusting Phase from 0 -180 and 180 - 360

Discussion in 'The Projects Forum' started by Sommer, Jun 3, 2011.

  1. Sommer

    Thread Starter New Member

    Jun 3, 2011
    Hey i'm making a Sub Bass Filter.
    And for that I am using a Linkwitz Riley filter for seperating the SW from the W, M and T.
    But I got a problem with the Phase.
    That's why i am looking for a circuit where i can change the Phase of an audio signal with one single Potentiometer. (Trim resistor).
    I found a way, but that is a bessel all-pass filter, that could only give me a delay from 0 - 50 degrees.
    But that is just not enough.
    Any of you know how i can make it?
    An example could be the Hypex DS 2.0
    On that product i can change the phase.
    Anyone know how i can make my own.
    I also found a bessel 2. order all-pass filter. but to change that from low delay to high delay i would have to change 2 resistors at a time. how could i do that with only one potentiometer.? (Trim resistor)
    Or any other helpfull answears is very welcome.
    maybe something completely different.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    One hardly imagines a person can actually hear a phase shift in the sub bass.

    However, if the audio fanatics have convinced you, Wikipedia has a way out -
  3. Sommer

    Thread Starter New Member

    Jun 3, 2011
    Ohh forgot to say that i am using a LR4... with 24dB/octave
    that means there is a 360° phase shift.
    But i really want to find a way to adjust the phase.
    that is the primary question.
  4. williamj

    Active Member

    Sep 3, 2009

    In responding, I am engaging in topics outside of my area of expertise. But many decades ago, in an electronics class, I learned a little about the resistive-capacitive (RC) citcuit. You may have already concidered and rejected this train of thought but here goes.

    I don't remember the math behind it but a resistor and capacitor in parallel will delay the phase of an AC circuit. As long as the components are capable of handling the voltages and currents applied in the circuit a RC circuit can change the timing from zero phase delay to 180° phase delay and beyond.

    By varying the resistance you vary the amount of time it takes to charge the capacitor thus delaying the phasing of the circuit. Atleast I think I remember that's how it works. If I'm worng somebody please step in and correct me.

    Good luck