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The Hopelessly Derailed ODAC/Objective DAC Anticipation/Discussion Thread

Discussion in 'Sound Science' started by maverickronin, Apr 29, 2012.
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  1. briskly
    To follow on another thread:
    The ODAC will hook up to a computer vs. the Clip+, which can only work off its meager internal storage and and attached micro SD card. Can be made to fit into the O2 and/or ODA and has a higher output to decrease the needed gain on associated amp.
  2. kiteki
    This is hopeless.  Verify that with an NwAv comment then, I'll ABX the ODAC and Clip+ for you!  Or my AckoDac AKD-23S.
    They don't all sound alike.  Repeating transparency over and over is only detracting from this project, people can most likely get the same price/performance ratio for cheaper from China anyway.
    Have a nice day.
  3. FoxSpirit
    Just to chime in, the Clip+ is NOT transparent. There is quite a bit of crud in there, obscuring very fine high level detail. In electronica, the "seams" of sounds will be much rougher. Basically distortion covering a bit of the signal. But it DOES still sound very good.
    With my M2C buds the sound is pretty wild when I go around shopping and need full blown setups of 5k+ to judge them favourably.
    Also, this: http://www.nosminidac.nl/sample__squarewave.html
    is a gross misrepresentation. But as is intended.
    Let's say ringing of this magnitude would generate a lot of noise whereas noise=imprecision of any kind and source from the tech side.
    The 0.04% THD compared to the 0.003% is easily explained, as nwavguy said, NOS designs have problems with IMD:
    CCIF IMD: This 19+20 Khz twin tone is a difficult test for many DACs running at 44 Khz. Old style (NOS) non-oversampling DACs especially struggle due to aliasing problems. In addition the output buffer (or I-V stage) in many DACs contributes high frequency distortion because the RC filter can be a challenging reactive load at these frequencies. If you look back through my reviews, you’ll find lots of products struggle on this test. Even the E10 turned in a marginal result. The ODAC, however, due to careful optimization of the output filter, and the superior digital filtering of the ESS DAC, does very well here with everything in the audio band well below 100 dB (both channels shown). Note also the 19 and 20 Khz tones are visibly equal in level which is not the case for many DACs:
    A atrocious filter nosminidac showed off may give bad results but something like the Sabre?? Whole different ballpark.
    Really looking forward to getting an ODAC+O2, I have a Mini-i to compare :wink:
  4. stv014
    A minor problem with NOS DACs is that the ringing they try to eliminate may already be present in the digital signal as a result of anti-aliasing anyway. Of course, on the graphs used for marketing, the edges are aligned to exact integer sample boundaries to hide this issue, however, with real signals that is often not the case. Here is a comparison of a 1 kHz anti-aliased square wave resampled from 44100 Hz to 352800 Hz with a simulated NOS-like effect, and sinc interpolation (ultrasonic content filtered out):
  5. AstralStorm
    I suppose one coould measure the AMP in parallel to the more real load of certain reference headphones, just in case the design is specifically broken.
    (e.g. at specific capacitance, impedance and/or phase)
    I wouldn't care too much about ringing anyway - many headphones ring far more on their own.
    In other words - these small amounts of ringing should be impossibly hard to notice on any headphone.
    However, they might cause oscillation issues in other parts of the circuit (assumiing there are any) - that's where proper design is required.
    You'd need something like really high end balanced armatures to even measure that. (Just see the frequency of the ringing; I assumed the square wave is 30 Hz, yes?)
    Or perhaps very high end electrostatic or orthodynamic driver - and that's really, really far yet from being able to discern this effect with both synthetic and live music.
    This is unlike THD+N or frequency response issues, since those effects are straight additive.
    DO IT THEN. Without all the necessary, expensive and validated (as in precisely described) setup of a double blind test, all you do is trolling.
    And not exactly for cheaper - the closest product out there that is about as good is probably FiiO E17 - and it's twice as expensive, has more features, but lower power output. It won't be able to drive the least sensitive (highest impedance) headphones reasonably.
    The other amps FiiO has made (I've singled out this manufacturer because they're one of the cheapest yet good amps) have non-transparent amounts of noise, minimally noticeable but still there.
    Yes, most people can hear -90 dB wideband noise with well isolating IEMs. It's even easier to hear a peaky noise - sounding whine-like.
    (Even highly isolating headphones don't have enough isolation and sensitivity to do this in the local environment for me.)
    The -96 dB is about the threshold of audibility of wide-band noise - part of the reason it's been chosen for the CD Audio. Note that ATH curves show the tone curves which tend to be less sensitive by at least a few dB.
    Note that I'm using 0 dB = 2 Pa - anything louder is really unhealthy for even short term. (Actually I calibrate loudness with multiple speech samples to sound properly loud, since I'm too lazy to measure this.)
    However, it's a very mild artifact compared to frequency response issues caused by high output impedance (common issue), or compared to larger amounts of IMD, which sounds really harsh.
    (Also what with many people are not measuring IMD right,)
    IMD and (huge) jitter issues are what can be perhaps attributed to sound "glass-like".
  6. kiteki
    I don't think I need to clear an ABX on the Clip+ versus ODAC in order for us to discuss the differences in sound.  Have you compared them yourself?  Have you connected both to a stereo receiver or portable amplifier?  That voids the potential output impedance issues.  I really don't think the vital differences in sound are in -96dB noise or jitter ...
    Ok ...
    - http://www.jdslabs.com/item.php?fetchitem=39
    - http://www.ebay.com/itm/AUDIOTRAK-Prodigy-CUBE-External-USB-Sound-Card-/110775770600
  7. AstralStorm
    Not ODAC unfortunately, I don't have one. However, I have compared Rockbox Clip+ vs same + FiiO E7; they're quite comparable, with E7 variant having noticeably lower noise floor.
    This difference alone voids any attempt at ABX, since you'll know which source is which just by the noise floor. Perhaps and ABC/HR grading test of multiple amplifiers would be in order? (this includes ABX of each)
    Could be fun to set up at a meet... Of course make sure to match levels precisely.
    Audiotrak Prodigy Cube - I didn't know of it, looks quite promising. I'd love to see some more info about it; esp. whether it's correct output impedance and about the driving power. (probably not too high if OPA2134 is running off 5V) It's pretty hard to mess up an OPA2134 design though, should be a great device indeed, perhaps I'll buy one.
    However, it's strictly for desktop usage.
  8. kiteki
    Here's one with external power then, you can listen directly from the RCA and adjust volume via software.
    Here is your ABX switcher device.
    I never asserted the Clip+ or ODAC total transparency, neither the price / performance ratio.  I still think the naked ODAC for $99 and DIY O2 are nicely priced though, as long as the Clip+ is not transparent.
    If it is
    - the ODAC hasn't achieved anything audible
    if it isn't
    - It should be outlined exactly where in the dScope - since the dScope can easily identify everything which is audible (another assertion).
  9. Raines
    is the ODAC que best DAC at its price?
  10. maverickronin
    What's your definition of "best"?
    I don't think there's a bus powered 24/96 USB DAC avalible for less and it's clean, clear, and neutral.
  11. kiteki
    Well it's certainly the most measured DAC at it's price.
  12. AstralStorm

    I'd love someone to take a stab at measuring the abovementioned Audiotrak Prodigy Cube before I commit my cash, I do need something nice desktop (but man-portable).
    Esp. output impedance. (The test is done with a multimeter and a r.) I'd like < 1 Ohm.
    I can pretty much assume rest is not broken - the lowpass could conceivably be, but it's unlikely, so a frequency response graph would be useful.
    TI TE8802 chip with the high quality DAC and output stage they put in there should be very high quality and low jitter, perhaps even comparable to Audio-GD's NFB-10.2.
  13. maverickronin
    Never heard of that one before.  Looks interesting.  Playing the odds it's not likely to have a low Z out but who knows.  If it does it would probably be good for IEMs and more efficient full sizes.  Can't do much more on USB power though.
    Also did AGD ever make something that measures well?  That's actually a serious question since they brag about not caring on their site.
  14. HaVoC-28
    Frequency response At least are fine [​IMG]
  15. maverickronin
    Well it's debatable how audible and how important -2.5dB@20khz is but filters can do a lot better than that.
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