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Headphones sensitivity, impedance, required V/I/P, amplifier gain

Discussion in 'Sound Science' started by xnor, Jun 15, 2013.
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  1. Meremoth
    Oooo, sweet thread.
    Could you add Audio Technica's ATH-AD900X? 
  2. xnor
    You're welcome and I'm sorry. Yeah the comma is our decimal separator and I totally missed it. Will change it asap.
    110 dB is what the peaks may come near to if you turn up the volume to the max. The RMS amplitude of music is always lower than a full-scale sine wave. How much lower depends on the type of music you're listening to.
    I'm still working on verifying the loudness calculations in my previous post, and I will also put up a warning.
  3. Wildstar
    There's something wrong there, surely the PX200s don't pull double the current of the K701s...
  4. xnor
    All analog pots suffer from some degree of channel imbalance.
    Especially at low volume the imbalance is bigger, gradually decreasing with increasing volume. At 10 o'clock, if you're unlucky, you can still have 1 dB imbalance but in that case I'd consider switching the pot.
    Rod Elliot writes:
    If the volume control is not an analog pot and does not suffer from channel imbalance it still makes sense to have such a broad usable volume control range, because higher gain will just add more noise, distortion. The volume control will also become touchy, so turning it a bit too far in the wrong direction could hurt your hearing.
    Stepped attenuators, for example, have fixed steps which you want to be able to use. Too high gain and you'll probably be forced to use some close to zero positions which are far apart in terms of step size.
    With digital attenuation you will reduce the effective number of bits quite a bit. Again higher noise etc.
  5. xnor
    I don't have measurement data on the X version, but added it based on manufacturer specifications.
    You are right. I still haven't had time to double check all the numbers. The problem with the PX200 seems to be low frequency leakage and high distortion at higher levels. Changed measurement frequency to 1 kHz.
    All these quirks are pointed out in the last "Notes" column.
  6. KamijoIsMyHero
    I'm not entirely convinced that argument is enough to have an ideal placement of 10 to 2. I might be missing some extra assumptions of the kind of amp that this ideal placement should be true of but a decent hi-fi amp shouldn't have this problem past 8-8:30 assuming 7 is the starting position.
    For the bolded part, my amp has 2 gains available http://www.audio-gd.com/Pro/Headphoneamp/Compass%202/Compass384EN_Specs.htm and I don't hear any audible noise that changes the music. I experimented with 16 vs 24 bit and I did hear an audible difference, a bit less with 24 vs 32 bit. So based on my experiment, I think this has to do with what the DAC is like as much as the amp, I set mine to 32-bit to minimize the noise as much as possible.
  7. xnor
    If it works for you I guess it's fine.
    The suggestion still stands though. The volume control should have a wide usable region, closer to max is better than closer to zero for reasons mentioned above.
    I know that many headphone amps have way too high gain. That's one reason I started this thread in the first place.
  8. Steve Eddy
    No such thing as too much gain. Gain is good. Tarzan want gain. [​IMG]
  9. vertical
    You're dating yourself :wink:
  10. xnor
    Sure, nothing wrong with driving PX100's with monoblocks with ~27 dB gain. 50 volts of headroom really make this headphone shine and sound better than an HD800!
  11. Steve Eddy
    Why not? I'm a cheap date and I put out. [​IMG]
  12. vertical
    Well, I hope to never partake in the experiment to prove those claims, but am happy to attest to your sense of humor...yes, I know, a subjective opinion
  13. ab initio
    "When you give to the poor, do not let your left hand know what your right is doing"
    -Matthew 6:3
    I do not mean to blaspheme in the science forum, but it was too funny I couldn't help myself!
  14. HalidePisces
    Can you add the following headphones?

    Audio Technica ATH-ANC7B (noise cancelling)
    Skullcandy Aviator
    Skullcandy Crushers
    Skullcandy Mix Master Mike
    Somic MH463
    Sony MDR-XB700
    Sony MDR-XB1000
    Superlux HD669
    Takstar Hi 2050
    V-Moda Crossfade M100

    The impedance of the Bose QC15 is very high...

    If you don't mind me asking, how was the gain calculated? It seems to be 104 - S@1V.
  15. stv014
    The gain calculation assumes a source output voltage of 2 Vrms. For lower voltage (portable) sources, obviously more gain is needed.
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