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Radsone EarStudio

Discussion in 'Portable Headphone Amps' started by m4rkw, Dec 12, 2017.
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  1. veraideishal
    I think the problem with the USB sound card is different from the problem with the Earstudio. On the USB sound card, it takes in uncompressed PCM data and outputs a voltage. If there is any aliasing, it's due to only that process (PCM to voltage, possibly due to bad rounding and a lousy anti-aliasing filter).

    With the Earstudio, if AAC (and the USB DAC output, if that gets tested) show no problems, then it is not the PCM to voltage conversion that is to blame (testing the USB DAC mode of the Earstudio is probably the best way to confirm this, since it is taking in PCM data directly).
    The problem then lies with the Decoder, which takes in either compressed SBC and aptX and converts to PCM. There is likely to be more problems that result from the decompression process.

    WS is probably asleep; it's the middle of the night in Korea.
     
    Last edited: Mar 5, 2018
    wslee likes this.
  2. SubMash
    I still need to test AAC properly. I don't remember now. I will test USB DAC also for sure.
     
  3. antdroid
    I cant try out your test right now. I have pretty weak LTE coverage at my office and also the phone mic picks up a ton of ambient noise. I dont know how accurate it would be.

    That said, are you hearing audible issues using apt-x with actual music/videos or just the test?

    I just listened to a couple songs and switched back and forth between SBC, AAC, Apt-X and AptX HD and i dont hear any clipping or any issues of note.
     
    wslee likes this.
  4. SubMash
    Ambient noise doesn't matter - if headphone will be at the microphone - it will overpower everything - you can see signal pattern.
    I started searching for the issue with Lana Del Rey and Soulsavers songs - on a high pitch clean tones I can clearly hear clipping.
    Btw, since I have 3 devices - I've tried them all.
     
  5. SubMash
    Some update - I tried AAC from iPhone X. RMAA for it is really bad. And, btw, I found out RMAA doesn't catch this issue well - I will post it later. But - there is NO aliasing or clipping on AAC on EarStudio although sound is not very sharp (and RMAA confirms it), but it's consistent. Look at those. So issue is with SBC/APTX encoders.

    [​IMG]

    Compare it with APTX on EarStudio:
    [​IMG]

    And here is AAC 17.4kHz tone - a lot of smooth harmonics.
    [​IMG]

    Still need to finish USB DAC
     
    Last edited: Mar 5, 2018
  6. SubMash
    USB DAC can't test today - there is -70dBA Noise Level which obviously is a ground loop.
    [​IMG]
    I need to think how to remove it tomorrow. It's midnight for me as well.

    I also probably need to redo the whole RMAA - it was on the 10kHz limit for THD.
     
  7. RobinFood
    Is there a way to get an earstudio in Japan? Amazon US and Canada won't ship here, and I can't find any resellers on ebay or aliexpress either.

    I need some kind of clip-on with bluetooth for my er4 when commuting, and was thinking of this as a solution that can keep the sound quality and let me take out the PtoS adapter.
     
  8. SubMash
    Got THD+Noise for all modes in EarStudio without ground loop issue. Noise in USB is unusually high.
    [​IMG]
     
  9. wslee
    All,

    I'd like to share some ES100 data measured using Audio Precision 2722 right next to my desk.

    [Test condition]
    - ES100 3.5mm output
    - No load
    - EQ, DCT off
    - AK4375a / sharp roll-off / 1x

    aptX (with Galaxy S8 source device)
    upload_2018-3-6_14-58-38.png

    It's just a lossy waveform codec using no psychoacoustic model.
    It uses QMF(Quadrature mirror filter) to split the input into a certain number of sub bands.
    And then it encodes each sub band with the limited bit allocation;
    more bits in the lower frequency band, less bit in the higher frequency band.

    SBC(SubBand Codec) also split the input into sub bands, but it allocates the same number of bits per for all sub bands.
    That's the one of the main difference between SBC and aptX.

    SBC is a very simple codec with low complexity.
    The low complexity nature was the primary reason for having SBC as mandate Bluetooth A2DP codec.

    And CSR released the new codec aptX with the key idea of allocating the different number of bits per each subband;
    more bits in the lower frequency band, less bit in the higher frequency band.

    So typical frequency response of a single tone would be as above.
    The noise floor is not flat across frequency ranges because the quantization noise from aptX codec loss makes the floor.
    aptX-HD performs better but the frequency response is similar to aptX classic.

    AAC (with iOS)
    upload_2018-3-6_14-58-58.png

    It's a complicated codec based on the psychoacoustic model.
    As you see below, the 1KHz and 10KHz tone is not sharp but shaped like a tower or triangle.
    The key idea of the psychoacoustic model is that;
    the signal or noise below the shape(i.e., Masking Curve) is not audible and not critical.
    Eventually we just need to allocate as less bit as possible for the target signal below the masking curve.

    So, the codec like AAC using the psychoacoustic model requires frequency analysis, the masking curve calculation for the time-varying input continuously,
    which cost a lot of processing power and power consumption.

    Since it's not a waveform coder, measuring THD+N for the signal through AAC codec has no meaning.
    Only perceptual domain performance would make sense.
    Anyway, AAC is more complicated than mp3, showing the better perceptual performance than mp3 at the same bit rate.

    USB (lossless, with iMAC USB)
    upload_2018-3-6_14-59-26.png

    It shows the baseline performance of ES100 HW.
    Unfortunately, ES100 USB supports 16-bit only, the overall THD+N is limited by the 16-bit PCM (-96dB), not by H/W.

    Please take a look at them all above.
    You will find there's no such a design flaw or HW defect as SubMash insist.

    If ES100 have any H/W issue, all the BT codecs, and USB would result in the same defect.
    Because all of them use the same H/W resource including DSP, DAC, and Power.
    SubMash mentioned AAC & USB sounds OK.
    Then it's not an H/W issue.

    And if we have the problem with aptX,
    how could we have ES100 in the Qualcomm's official aptX product list?
    They have their own qualification and certification process for aptX enabled products.
    We sent ES100 to them for their testing and finally had ours on the list.

    https://www.aptx.com/products/radsone-earstudio-es100-bluetooth-receiver-headphone-amplifier

    Lastly, I just took a look at the SubMash test results and graphs from his mobile phone screenshot.
    It seems that he ran the test with his mobile phone.
    Anyway, as I see them, those results are showing the tremendous and unacceptable noise.
    If those graphs are indeed real and represent ES100 output,
    the sound would be considerably worse than the expected,
    and everyone would definitely notice the defect right at the start.

    We can't deceive many thousands of ES100 users.
    The users are not fools and would notice the that much of conspicuous defect very easily.

    Thanks and Regards,
    WS
     
    Last edited: Mar 6, 2018
  10. myusernameislove
    I tried it with my Sony xPeria XZ1 BT5 smartphone and Audio Technica AT-PHA55BT receiver with SBC, AAC, Aptx, LDAC support (no AptxHD), and LDAC, AAC, SBC is fine, but with Aptx I hear some sand.

    edit/ I also tried my phone with Inateck BR1006 receiver with SBC, AAC, Aptx, AptxHD. SBC and AAC is fine, but with Aptx and AptxHD I hear some sand again.

    There is two times longer sand noise with Aptx then with AptxHD on Inateck. The length of sand noise with Aptx on Inateck and on AT is about the same. The sand noise appears twice (two peaks) at higher end of the spectrum.

    I have also heard one or two clicks with both units and all codecs (even LDAC) but after I repeated the test the click was gone, so I guess it is OK. Yes, I tested LDAC in all priority modes.
     
    Last edited: Mar 6, 2018
    bidn and wslee like this.
  11. SubMash
    So problem not only sand. It plays in the beginning sound that is NOT the tone itself, but harmonics at the lower frequency instead. And you can understand it, because tone should go linearly down and if instead it's moving up/down or doing steps - it's not the tone you hear - it's garbage.
    I can confirm that sand is everywhere, but with EarStudio it's way stronger - I have a suspicion that load + oversampling influences noise. I need to check it again.
     
  12. tim0chan
    Using the es100 now, no issues with noise etc. With aptxhd it sounds better than with my LG g6 with quad dac
     
    scotvl and wslee like this.
  13. wslee
    @myusernameislove:
    Can I ask the sand noise you're experience is with the test tones or sweeping chirp?
    Just want to check if you hear the noise only with the test signal or also with regular music sources.
    Thanks and Regards,
    WS
     
  14. m4rkw
    @wslee is there any update on UK sales? I was told on twitter that they would begin early this month.
     
  15. wslee
    @m4rkw, @PantsUK:

    I'm so sorry we're still working on it but having some problem with the shipment to warehouse.
    We'll open AMAZON Europe no later than the end of April.
    Sorry and appreciate your patience.
    WS
     
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