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

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

  1. cskippy

    cskippy Creamy warmpoo

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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.
     
  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.
     
  3. johnjen

    johnjen Doesn’t want to be here but keeps posting anyways

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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 Red eyes from too much anime

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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.
     
  5. mrflibble

    mrflibble Friend

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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 Traded in a unicorn for a Corolla

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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
  7. johnjen

    johnjen Doesn’t want to be here but keeps posting anyways

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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 Traded in a unicorn for a Corolla

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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.
     
  9. johnjen

    johnjen Doesn’t want to be here but keeps posting anyways

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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 :)
     
  10. TomHP

    TomHP Facebook Friend

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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 Doesn’t want to be here but keeps posting anyways

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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 Traded in a unicorn for a Corolla

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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.
     
  13. Justin S

    Justin S Friend

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    Super cool! I found this thread from a basshead.club article on the RME ADI-2. I am trying this in the nearfield setup at my suite right now.

    W10 Roon>HQP>USB>Intona>USB>RME ADI-2 DAC fs>BAL>Schitt Freya>BAL>Neumann KH120As

    I reversed the polarity of the right channel in the rme interface and inserted a polarity reversing XLR adapter (Whirlwind IMP) on the right channel of the RME.

    I think the difference is subtle, but it's there. I feel that it adds some depth to the staging, and more presence/detail in the lows and lo mids.

    Like @Luckbad , I will put some more time into listening and report back.
     
  14. Elmer Danilovich

    Elmer Danilovich MOT:Earmen, HeadAmp, Bricasti; AKA:MShenay

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    Ah I forget I never got a chance to chime in here, I too think it does make a subtle difference and have found the difference to be pretty consistent in both fully balanced all in ones and running balanced out from a DAC into a Balanced Amp

    I also felt while it did make small improvements to staging it also helps to flesh out low frequency spectra, so small but noticeable improvements to texture/slam.
     
  15. Justin S

    Justin S Friend

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    So I've tried a couple of variations on this over the past week: reversing the polarity of the right channel in the RME and then installing a polarity reversal adapter on the right channel of the DAC output (very subtle) and then moving the polarity reversing XLR to the output of the Freya (bigger change in the sound - makes sense).

    It is subtle if you try A/Bing it quickly. I found the biggest difference comes when I have been listening to the system with the single channel phase reversal + adapter on the Freya output for a while and then I remove it. Everything becomes flatter, the bass is less interesting. The overall sound is less engaging.

    This is an effective tweak in my work suite. It is effective enough that I am going to keep my RME ADI-2 DAC fs (long story short, I was ready to put it up for sale - perhaps a topic for the RME ADI thread). Total cost was $30 for the XLR phase reversal adapter (which I purchased many...many years ago).
     
    Last edited: May 23, 2019
  16. k1arg

    k1arg Facebook Friend

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    If I understand correctly (not to be trusted), for a fully differential end-to-end (or whatever terminology) amp, this could be implemented internally to the amp itself, right? That is, couldn't it be done by just changing the wiring of one input XLR connector and analogously on one channel of the output XLR connector. Does anyone know if this is effectively done already by any existing amp topology? It seems like an easy to implement circuit optimization, so surely someone must have thought of it several decades ago. :)
     
  17. dllmsch

    dllmsch Friend

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    Resurrecting an old thread.
    Have been using this method for quite some years, didn't really compare to anything since I'm using vali 2 with one tube and assume it just being better, chain was:
    Shitty laptop>foobar2000>modi multibit v1>vali 2>Atticus

    Now that I got the BHA-1 and finally have the time to create a balanced HD6XX cable, I did some comparing today. Might totally be placebo but I think listening to HD650 with single channel polarity reversal I got a tad bit better instrument separation. It was extremely subtle tho. chain was:
    Pi2AES>modi multibit v1>Bryston BHA-1>modded HD650
    music file converted with foobar2000 dsp vs normal music file

    Since this is just a do it once and never have to look back mod, it's worth a try even if it does nothing, at least it won't hurt!
     
  18. wormcycle

    wormcycle Friend

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    The same amplifier, and the same impressions like yours. I tried with HD800S and HEKv2. And just marginally cleaner bass.
    But taking into account the "theory" behind all this, see the quote below, why would it make any difference on a balanced amplifier?
     
  19. dllmsch

    dllmsch Friend

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    I am no electrical engineer but my guess would be both normal and inverted signal on one channel needs voltage to drive it actively? Hence flipping one channel balance it out even the signal is +- -+? I read somewhere that balanced output have double the voltage swing compare to SE.
     
  20. wormcycle

    wormcycle Friend

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    Some more experiments with phase reversals on RME ADI-2 Pro balanced headphone out.
    Phase reversed in Roon, right channel, reversed back in the RME to 4 pin XLR adapter.
    Very different results with different headphones and also different than on BHA-1.

    1. HD800S - immediately very fatiguing, no improvement in bass
    2. HE500 - sound more open, that effects is very obvious, slightly brighter , not fatiguing but loose a lot of their smoky magic.
     

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