UltraSonic Studios Oblivion Review

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Feb 6, 2020.

  1. purr1n

    purr1n Finding his inner redneck

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    THDN vs dBu (input) into 30-ohms and 330-ohms.
    To arrive at output dBu, add +13.22 gain.
    upload_2020-2-7_19-39-58.png

    We get to around -4dBu input before we hit the knee were clipping starts to occur. That would be 9.22 dBu at the output, which is about 2.2Vrms. I'll let you guys to the power numbers yourselves. Everyone on SBAF should be able to do this.

    Note that the typical use range between -25dBu to -15dBu at the input (about -12 to -2 dBu at the output) is in the ideal sweet spot of the amp in terms of THD+N which is a just a bit better than 60db. While I would have liked to see more margin against 60db some SINAD, the measurements shouldn't really present an issue, unless one listens to bassy headphones or bassy material.
     
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  2. Roget

    Roget Rando

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    [​IMG]

    Purrin, you say from your listening test "Bass quality isn't bad, but I don't it's the clearest and it doesn't quite keep up with the highs."

    Is your opinion the measurement above supports your listening?
     
  3. cskippy

    cskippy Creamy warmpoo

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    Eager to hear about Oblivion on speakers.
     
  4. purr1n

    purr1n Finding his inner redneck

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    Got those impressions in a bit. But before that, some speaker relevant measurements.

    Oblivion into 8-ohm load. 0, -10, -20dBu (red, green, and blue respectively).
    upload_2020-2-9_11-35-53.png
     
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  5. purr1n

    purr1n Finding his inner redneck

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    This time into 4-ohms. Not much different from the 8-ohms results. A bit higher, but same distortion shape.

    Oblivion into 8-ohm load. 0, -10, -20dBu (red, green, and blue respectively).
    upload_2020-2-9_11-49-12.png
     
    Last edited: Feb 9, 2020
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  6. purr1n

    purr1n Finding his inner redneck

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    Oblivion THDN vs input (dBu) into 8 and 4-ohm loads.
    To derive output amplitude, add +13.22 dBu (e.g., -13.22 on the X-axis is 0dBu or 0.775Vrms)
    upload_2020-2-9_12-5-35.png
     
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  7. purr1n

    purr1n Finding his inner redneck

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    It's actually pretty good. Compared other amps, the EC Aficionado cannot drive these big JBLs because the woofers are 4-ohms. The Aficionado OPTs are designed for 8-ohm impedances. I don't like the Studio Jr. without feedback either (too soft and rolled, especially with the 300Bs). The Studio Jr. with feedback is another story.

    IMG_20200209_122555.jpg
    I actually posted the measurements first (not impressive in many ways) because I wanted to demonstrate how measurements need be properly interpreted depending upon use case. With the big JBLs, I get well above 80db SPL at the listening position with 0.2Vrms on the outputs. 0.2Vrms is -12dBu. -12dBu output would be about -25dBu on the x-axis in the THDN + frequency axis above which on the green line (4-ohm) would be 50db SINAD for the 4-ohm woofer and 60db SINAD for the 8-ohms mids and highs.

    Now before something accuses me of double-standards or opposing goalposts, I've already been on record on what constitutes a good measurement here: https://www.superbestaudiofriends.o...ically-incorrect-audio-blog.7261/#post-249242

    60db SINAD I have no problems with. And it would also appear that most members who tried on various listening tests with their own headphone gear can't distinguish better than 35db of THD. Yes, 50db THD is not what I could call good, but in reality only driver past 15" are going to have lower bass distortion than 50db THD.

    I would say however that I as turn up the volume from 80db+, the Oblivion doesn't quite have enough juice. The bass is tight, the transients sharp, but the volume and heft of the bass is less and less as we get louder.
     
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  8. Roget

    Roget Rando

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    The distortion from the amp adds to the distortion from the woofer. Garbage in garbage out.
     
  9. purr1n

    purr1n Finding his inner redneck

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    In the case of the big JBLs, you are right. This is consistent with what I am hearing at higher levels, and again, you would need to prove to yourself through controlled tests that you can hear 50db THD.

    However, I would argue that few people run clean 18" woofers, not even 12". A typical home HiFi speaker will probably have -40db THD woofer. Say the amp is 52db SINAD, it resultant distortion still isn't much higher. The reasons for this is that db is a relative logarithmic scale. It's not like 50db SINAD + 40db SINAD becomes 10db SINAD. You need to convert to voltages, add, then back to db.

    So for the hypothetical example of -40db THD woofer and -52db THD amp. The output at the woofer in theory would be only -38db! It's actually way more complex than that since you would need to sum the amp and speaker FFTs in voltage levels before doing an THD calculation on it.

    I would suggest that you try a controlled listening test to see if you can hear the difference between -38db THD and -40db THD for any signal.
     
    Last edited: Feb 9, 2020
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  10. purr1n

    purr1n Finding his inner redneck

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    Anyway, to follow up, what I heard with the Verite held up with the JBLs at low to moderate volume levels. Good clarity and crispy transients (despite measurements). Wide soundstage, although it was flat. The sound is less like the EC DHTs, Pass XA25, Aegir, M22, etc. and more like the Crown CDi1000, but without the CDi1000s heft, separation, and incredibly layered soundstage. Maybe a bit crispier up high and softer in the lows (even moreso as we crank it up).

    I'll get back to trying out some other headphones with it and report back.
     
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  11. nishan99

    nishan99 Rando

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    That's about 1-1.26% THD and anyone can check this out in the video below.

    And apparently we are way less sensitive for bass distortion, I myself only noticed it when it's about 8% and that's with a test tone and not actual music.

     
    Last edited: Feb 29, 2020

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