Hep me...noise floor...

Discussion in 'General Audio Discussion' started by GoodEnoughGear, Jun 9, 2016.

  1. GoodEnoughGear

    GoodEnoughGear Evil Dr. Shultz‎

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    Hi folks,

    I have a question about noise and noise floors.

    The LG V10 has an ESS 9018 DAC and ESS 9062 amp built in. It has three 'modes' which deliver increasingly greater power: 'Normal' for low-impedence headphones, 'Aux' for external devices and then 'High Impedance' for high-impedance headphones.It auto-senses these modes, but you can trick it into 'Aux' mode by attaching an extension cable, and then plugging in your low-impedance 'phones in. I don't have any high-impedance phones, but you can do a similar trick to get into 'High Impedance' mode by attaching an extension to the phones, plugging them in and then unplugging from the extension which leaves you in HI mode.

    Anyway, I noticed in 'Aux' mode that there is easily audible noise with my IEMs (se215). The track I am using is Stacy Kent's 'The boy next door', and the opening bars of the track reveal the noise easily. With more careful listening, I noticed that the noise actually follows the audio (in this case discrete bass notes), almost like a shadow, swelling and receding with the bass notes. However it does not appear to increase in volume as you turn the volume up. For example if I listen to the opening bars in 'Normal' mode and then volume match in 'Aux' mode, I hear the noise much more clearly in 'Aux' and it's all but imperceptible in 'Normal'. But I can turn the volume up all I want and there's no apparent increase in either mode.

    I always assumed noise floors were white noise type stuff with no structure, related to simple operation of an amp. But the V10 goes black when nothing is playing, almost like they're cutting the amp out. So I tried playing a silence track (generated by JRiver), expecting to hear noise, but there was no noise evident, it sounded just as black as when no playback was happening. So it appears there's no inherent 'noise floor' per se.

    So what the hell is happening here? Is it interference from the DAC bleeding over to the amp, or is it more likely originating in the amp itself but affected by the incoming signal? Is it even correct to refer to this as a noise floor, given it's related to the signal?

    I'm not trying to fix this in any way, I'm just curious what may be going on.
     
  2. T.Rainman

    T.Rainman Acquaintance

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    sounds like the noise floor is in the recording (noise gates used ?)

    Line-out and high-impedance settings probably only differ in gain.
    As the gain is higher the noise floor of the recording is higher in level as well with the IEM's being so sensitive.

    Don't think LG has crappy filtering going on inside .. but who knows.

    If 'real silence' and 'mute' both have inaudible noise levels chances are noise isn't a DAC thing unless signal handling is done very wrong.
     
  3. GoodEnoughGear

    GoodEnoughGear Evil Dr. Shultz‎

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    Thanks for the feedback - you prompted me to do some more testing:
    • It's definitely not in the recording - I don't hear it using either GOV2 or Mojo, and I hear it similarly on any track I try, though quieter tracks make it easier to pick out.
    • It's definitely a 'floor' in the sense that the volume of the noise doesn't increase with volume adjustment, only gain increase between modes.
    • I can actually detect it in 'Normal' mode, though it's almost imperceptible.
    • It definitely is related to the signal (that shadow effect is evident in all cases).
    Either I have a bum unit or my hearing is better than I thought. Certainly better than the se846 users on HF who are claiming the V10 is dead black :). Or maybe I have just learned to listen a bit better.

    Now that my ears know what to listen for, I can't un-hear it. Thankfully it's essentially inaudible in 'Normal' mode, which is good enough for casual use. But it is a pity it's there at all or this would be a serious DAP challenger.
     
  4. T.Rainman

    T.Rainman Acquaintance

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    Having chips like ESS 9018 DAC and ESS 9062 isn't insurance things will sound good.
    Power supply decoupling and PCB layout as well as digital processing implementation can play a bigger role here.

    Possibly the internal software handling the audiostream is at fault here.
     
  5. Jun

    Jun Friend

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    Try it on flight mode.
     

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