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Help me get back in phase!

Discussion in 'Effects [BG]' started by kesslari, Dec 12, 2017.


  1. kesslari

    kesslari Groovin' with the Big Dogs Staff Member Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
    I've got phase issues...
    I put an ACG02 preamp in a stomp box.
    It's a filter-based preamp designed by John East. It has a low-pass filter stack and a high-pass filter stack, and is designed for on-board installation. But I put it in a box.

    So far so good.
    But - I want to blend it with the unfiltered sound of the bass.
    So I got a Boss LS-2, which *seems* like it would do the trick. But the problem is that the output of the ACG is out of phase with the unfiltered signal.

    Oh FX Gurus, hear my plea! Help me get back into phase!
    @johnk_10 - any ideas?

    Thoughts:
    1. Put a pedal that inverts phase after the ACG. Qualities desired - small (1590a), does not modify the sound, high quality, inexpensive.

    2. Build a phase inverter and put it after the ACG. Ideally in a 1590a box. I found this page Operational amplifier applications - Wikipedia but would really benefit from a specific circuit or parts list. This could be an "always on" as it would only be in the loop with the ACG.

    3. Replace the LS-2 with something else. Again, the goal is to be able to take the ACG in or out of the circuit, blended with the natural sound of the bass. The blended or natural bass sound would then go to the other effects in my board.

    Specific recommendations, other ideas, and good jokes welcome.
     
    Last edited: Dec 12, 2017
  2. Fill me in, what’s an ACG02
     
  3. kesslari

    kesslari Groovin' with the Big Dogs Staff Member Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
    Updated original post.
     
  4. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    you'd just need a simple single stage buffer amplifier in a 1590A to use it with your LS2
     
    kesslari likes this.
  5. After looking at the EAST stuff, I would suggest talking to them. Probably more going on than couldn’t be fixed by just a simple 180 phase flip, may be some inherent phase shifting as a result of the EQ and pass filters being used, they can cause phase variances. Probably would need to be measured.
    If you’re noticing audible phase issues, you may not be able to blend the signals that way. Just my opinion, ready to learn if there’s another answer!
     
    Last edited: Dec 12, 2017
    Domespeed and kesslari like this.
  6. How would a buffer affect phase issues in this case, is impedance at fault? :help:
     
  7. kesslari

    kesslari Groovin' with the Big Dogs Staff Member Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
    A single stage op-amp inverts phase.
    Question - how can I tell if a commercial buffer is single-stage?
     
  8. Alien8

    Alien8

    Jan 29, 2014
    You can't unless they advertise it specifically. Most buffers do not invert the signal, based on the design, but some certainly will. You could contact the builder too.

    If you want to build your own, check out this page, at the bottom: Basic Buffers

    Otherwise, I'd sell the LS-2, and look to the OneControl Mosquite Blender to save space Mosquite Blender with BJF Buffer. Pricy, but usually found for reasonable price used.
     
    johnk_10 and kesslari like this.
  9. kesslari

    kesslari Groovin' with the Big Dogs Staff Member Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
    I was just coming to that conclusion myself after doing some reading this morning. Thanks!
     
  10. Depends how its wired. It can be inverting or non-inverting.
     
  11. kesslari

    kesslari Groovin' with the Big Dogs Staff Member Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
    Just bought a Mosquite Blender. I should be set.
     
    Tom Bomb likes this.
  12. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    great choice!
     
    kesslari likes this.
  13. micguy

    micguy

    May 17, 2011
    I was gonna suggest that, but got beat to it - I have one, and it works really well. Good choice!
     
  14. non

    non

    Aug 4, 2015
    not that i know anything about phase problems but could it be that the acg02 preamp is taking a ever so slightly longer time to process the signal than the ls2 so you are actually getting lag from the preamp. just a thought.
    i use the ls2 with no problems.
     
  15. bumperbass

    bumperbass Supporting Member

    Jun 19, 2012
    Lag is still a sort of 'phase thingy'.
     
  16. Gizmot

    Gizmot Supporting Member

    Mar 22, 2009
    Nashville area
    Let’s be technically correct and precise here - you keep saying PHASE and what you really mean is POLARITY - right?
     
  17. superheavyfunk

    superheavyfunk

    Mar 11, 2013
    Toronto
    Many blenders have this option. I used the Xotic X-Blender for a long time for this purpose
     
  18. boomertech

    boomertech Frank Appleton Supporting Member Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    Phase inversion is also technically correct.

    -Frank
     
    Loring, ddnidd1 and johnk_10 like this.
  19. Gizmot

    Gizmot Supporting Member

    Mar 22, 2009
    Nashville area
    Sorry Frank -it isn’t. In audio engineering terms, phase equates to time. What’s happening in this case is that the plus and minus of the signal are being electricallly reversed.
     
    aborgman likes this.
  20. boomertech

    boomertech Frank Appleton Supporting Member Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    Sorry Gizmot- it is! I have been an electronics engineer since the 80's and "phase inversion" is a term that was used in my text books in college. Phase inversion does not involve time, it is the same as flipping the polarity. Goggle it.:thumbsup:

    -Frank
     

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