Twisty/Turn-y Things: Single Channel Polarity/Phase Reversal

Discussion in 'Modifications and Tweaks' started by Torq, Oct 3, 2016.

  1. cskippy

    cskippy Friend

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    Ah, the cable IS wrong. I retested today and was just looking at the pins but forgot that they MIRROR each other on the other end, and to make sure, like you said, to follow pin 1-1, 2-2, 3-4, and 4-3. So channels are reversed as well as polarity between channels. Damn. I'll get it rewired and post back.
     
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  2. Garns

    Garns Friend

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    I'm getting the bits in to try this out. What really pushed me to try it is @atomicbob's comment over in the system synergy thread that this can work with a completely single ended system.

    This probably bears repeating here for those who didn't see it. The only balanced part one actually needs is a 4-pin XLR termination to the headphone. To use with a SE headphone amp, plug the phase reversal cable into the headphone, then use a balanced to SE headphone adapter to plug the other end of the phase reversal cable into your headphone amp. Finally, reverse the phase of one channel in software and you are done.

    I will be trying this with Valhalla 2.
     
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  3. johnjen

    johnjen Friend

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    I'm always interested in reading what other people hear while using this tweak.
    For me personally I have never had it NOT make a difference, and what I find interesting is to come to know what changes, others hear as well.

    JJ
     
  4. Grahad2

    Grahad2 Friend

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    Well if you're on old 2pin IEMs then it's easier, since the connector is reversible. A simple plugin that offers L, R, and L&R invert for foobar2000, then you just flip one side of the connection on the IEM side.

    So technically you get audio path of (L invertR) from the PC all the way till the driver/crossover.
     
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  5. mrflibble

    mrflibble Almost "Made"

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    I have yet to makeup the cables and try this out yet. But I have been playing with Linux and ALSA to invert one channel, here is the relevant excerpt from my ALSA configuration:

    Code:
    # Invert one channel
    pcm.invert {
      type ladspa
      slave.pcm "plug:bit_perfect"
      path "/usr/lib/ladspa"
      channels 2
     
      plugins {
        0 {
          id 1429
          label inv
          policy none
          input.bindings.0 "Input"
          output.bindings.0 "Output"
        }
       
        1 {
          id 1181
          label amp
          policy none
          input.bindings.1 "Input"
          output.bindings.1 "Output"
          input {
            controls [ 0 ]
          }
        }
      }
    }
    
    pcm.invert_plug {
      type plug
      slave.pcm "invert"
      
      hint {
        show {
          @func refer
          name defaults.namehint.extended
        }
        description "Invert One Channel"
      }
    }
    It could probably be optimized to remove the amplification of the second channel (I haven't figured that out yet), I'm using it with a value of 0 as a dummy conversion for the other channel. The bit_perfect plug is my plug for bit perfect playback, substitute your own plugin or mixer depending on your configuration.

    The configuration utilizes the LADSPA plugins, and you will need to have these installed (probably via your package manager).
     
  6. Luckbad

    Luckbad Thinks this is blogspot.luckbad.com

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    Decided to do this today since I was already soldering in some power caps on my Orchid DAC and had the iron out.

    I can certainly convince myself that I'm gaining something in headstage. Or it could all be in my head. Initial impressions are definitely not that it hurts anything, so that's a good thing.

    Maybe a little cleaner in the low notes.

    I feel like I'm perceiving more than this, but I've also decided I'm probably suffering from confirmation bias.
     
    Last edited: Aug 30, 2017
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  7. johnjen

    johnjen Friend

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    My advice is give it time for you to hear more of your music and acclimate, then undo this PRT and then compare again.

    Some times the changes this tweak makes are close to the ToP (Threshold of Perception) and a bit of 'training'/experience helps to focus in on and reveal these details.

    It should be most especially evident in the very bottom end where the bass should gain additional details and impact.
    IOW the visceral impact should be enhanced.
    This of course means that only the music that still contains the very lowest couple of octaves of musical information will be helped by this tweak.

    But also the mids can become more detailed with tighter focus resulting in hearing into the music to a greater degree.

    JJ
     
  8. Luckbad

    Luckbad Thinks this is blogspot.luckbad.com

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    I've been using the PRT as described in this thread for a couple of weeks now.

    At this point, my standard HD650 cable has been hard modded to just have right channel inverted. This tweak is now virtually indispensable in my main setup.

    If I go for a few days using it all the time, then go back with my adapters, everything gets worse. Soundstage, bass, cleanliness.

    This seems like snake oil with a side of pseudoscience and a dash of expectation bias, but I like it. A lot.
     
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  9. johnjen

    johnjen Friend

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    This tweak lends itself to redefining just what is and isn't unadulterated Snake Oil™©®.

    No purchase necessary, not available in stores, void where prohibited, actual cash value 0.1¢, no snakes were harmed during the making of this tweak, satisfaction determined by the end user, your mileage may vary…

    "Try It you'll Like It"™©®

    JJ :)
     
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  10. TomHP

    TomHP Almost "Made"

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    Would this at all be measurable? E.g. THD vs. output level on a single channel but feeding the same signal either in or out of phase to the second channel?
     
  11. johnjen

    johnjen Friend

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    It might be, but most tests use simple wave forms and this tweak can yield subtle differences when using music (complex wave forms), so the measurements I would tend to think, would be even less obvious/harder to detect using test signals.

    But really this tweak either results in a beneficial change, or not, for you in your system.

    JJ
     
  12. Luckbad

    Luckbad Thinks this is blogspot.luckbad.com

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    Of potential interest: phase reversal is non-destructive, at least according to the Sonic Frontiers' HDCD detection light. If you change anything about the signal, it doesn't light up. For whatever reason, phase reversal on one channel doesn't cause the dac to complain.
     
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