xDuoo TA-66 OTL Tube Headphone Amplifier: A Kind of Magic

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Jan 15, 2025.

  1. purr1n

    purr1n Desire for betterer is endless.

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    What sorcery is this? A couple of guys mentioned this little $250 Chi-Fi gem. OMG. This is not only is high-value Golden Schlong, but gets awfully close to an Excellence award if not outright deserving one.

    ta-66.jpg

    The only thing I dislike is the clunky volume stepper - honestly I wished xDuoo just used a cheap pot - however I found the volume granularly acceptable with the HD800. Sure, many of us haven't heard of xDuoo because it's some of those oddball Chinese brands, but they've made decent stuff before: https://www.superbestaudiofriends.o...ble-dac-headamp-review-and-measurements.9655/

    @atomicbob's technical measurements: https://www.superbestaudiofriends.org/index.php?threads/xduoo-ta-66-technical-measurements.14907
     
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    Last edited: Feb 3, 2025 at 6:42 AM
  2. purr1n

    purr1n Desire for betterer is endless.

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    Some bullet points here to highlight what was said in the video:
    • Holy crap, resolving of fine detail. We used the Magni Unity as reference because so many people are familiar with its sound. It's a very good sounding solid-state amp with smooth highs and high engagement factor. Lindsay switched to the TA-66 from the Magni Unity and thought it was broken because she heard some hiss, but only when the music was playing. After a double take, we realized the recording had the same hiss from the Magni Unity too, but the TA-66 just presented it more clearly, a result of it being more resolving and able to layer and separate the soundscape better.
    • Isn't as strong in the lowest bass, but punchier midbass. This is probably something that can be expected from a OTL design with high-output impedance. The Magni Unity wins in the bass control and deep bass department and thus were our preference for various Daft Punk and Aphex Twin tracks. The TA-66 is looser in the lows, but not appreciably so. The bass articulation and control is along the lines of an EC Zana Deux. There's a bit of bloom which is a nice touch. But it's not warmpoo or anything distorted like the WA-2 or Leben CS300 which WTF sound broken with the HD800. This is the kind of tube gear that gives people the wrong impression and enables objectivists who measure distortion at voltage levels capable of killing headphones and definitely making you deaf.
    • For most everything else, Tom Petty Casa Dega, Tracy Chapman, Connie Evingson, Joni Mitchell Blue, Springstein Man on Fire, Fleetwood Mac, the TA-66 was preferred. I was surprised that Lindsay used the word "dry" for the Magni Unity when switching from the TA-66 - as we have often used the words wet and dry. With respect to the wetness, it isn't anything like the obscene overblown shivering wetness of this: https://www.superbestaudiofriends.org/index.php?threads/feliks-audio-elise-tube-amp-review-not.2260/ The TA-66's transients are slightly more rounded, but not much more so, compared to the Magni Unity.
    • The headstage is quite expansive and I think actually on par with something like a DNA Supernaut. It's just a bit smaller than an EC ZDS and definitely has less depth and layering than my EC custom: https://www.superbestaudiofriends.o...-studio-45-custom-headamp-measurements.10073/
    • Compared to the EC custom, the TA-66 takes the edge off the HD800's etch just a bit more. However I would not call the TA-66 rolled in the highs. The TA-66 also lacks that final bit of clarity. Hey, it's OTL and that cap is gonna get in the way no matter what. Still I'm impressed and curious what the designer chose for the coupling caps. The EC custom pulls off better microdynamics, faster micro-swings, and has an overall more refined character.
    • No way the TA-66 should sound this good. Kudos to the designer. Long live Chi-Fi. The TA-66 exemplifies the best of Chi-Fi: non-insipid reproduction of music with solid technicalities at an unbeatable price. Not flat and boring high-feedback designs that measure well but sound meh.
    • Not familiar with the 6NP5 output. Curious if it's plate coupled (instead of cathode).
    PXL_20250115_200503103.MP.jpg

    Very Strong 2025 Contender for Golden Schlong Value and Excellence. Belongs in HD800 Recommended Amps: https://www.superbestaudiofriends.org/index.php?threads/best-amps-for-hd800s-2023-edition.13859/
     
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    Last edited: Jan 15, 2025
  3. purr1n

    purr1n Desire for betterer is endless.

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    P.S. It sucks for orthos. Low impedance Grados are good, fantastic (depends what you are looking for) as long as the bowl pads (not F) are used. Still, high-impedance headphones are the way to go.
     
    Last edited: Jan 15, 2025
  4. Case

    Case Anxious Head (Formerly Wilson)

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    Sounds like what I wanted Valhalla 2 to be.
     
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  5. purr1n

    purr1n Desire for betterer is endless.

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    Single Ended Triode FTW. I found out the 6N5P is the 6AS7.

    The downside for this design is low power. This reminds me of one of Craig's first amps, the HD51 or whatever it was called.

    These xDuoo guys aren't Fing around. Sure, they are not using exotic boutique caps, the caps mean EVERYTHING for these kinds of designs. However, it appears they took time to choose parts that sound good. Something listened to the design... This heartens me because I am assured not all Chinese designers look at AP-555 measurement results to determine what sounds best. I am so happy we have good Chi-Fi. Amir and ASR set back Chi-Fi 7 years.

    ta-66-headphone-amplififer-1.jpg
     
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  6. roshambo123

    roshambo123 Friend

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    @purr1n, any tasting notes in comparison to the DarkVoice OTL? Be nice even to have something similar at the same price without the wrong voltage transformer
     
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  7. Ash1412

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    @purr1n Can you measure the output impedance? They're saying 5.5Ohms on HF but I have a hard time believing an OTL can get that low easily.
     
  8. fraggler

    fraggler A Happy & Busy Life

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    Also requesting some notes vs the SW51, particularly with HD800. I was going to move completely away from tubes since I have the MJ3, but always a bit curious.
     
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  9. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    I'm currently reviewing their TA-84 and it's very good. Microphonic tubes and a cursed stepped pot aside.
     
  10. Wilewarer

    Wilewarer Almost "Made"

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    I was wondering whether there was a good actual budget tube amp to try with HD800, but I'm sort of in disbelief at what this is supposedly competitive with. Is it just that nobody was even really trying to make something like this outside of megabucks boutique stuff?
     
  11. Nick76

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    Ha, knew you would like it, thing is unbeatable for it's price with 800S and 650/600, few build quirks aside. I gotta buy another since my first unit had a relay pot problem that would mute the left channel every couple of steps. And yes that knob is clunky as all hell.
    [​IMG]
    [​IMG]
     
  12. purr1n

    purr1n Desire for betterer is endless.

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    I think it's similar, although don't want to say much because it's been a while. Also I don't think I have heard a DV336 that hasn't been modified in some way. Darkvoice 336 uses the 6SN7 which I prefer over 9-pin types. On the other hand, I feel the TA-66 out of the box has more attention paid to parts selection, which is crucial (it doesn't have to be $$$ boutique parts).

    I didn't care for the TA-84, at least the Drop version. I mean I guess it's not bad. However, TA-84 is PP not SET. PP subtracts information from music at with the advantage of more power. I also dislike the sound of EL-84 tube. Also Triode vs. Pentode. However for planars, the TA-84 may actually work better??? I can confirm that the TA-66 sucks balls for planars - basically unusable with the ZMF Calera. TA-66 Z-out is just too high and power too low.

    With the HD800, no doubt the TA-66. Just wetter, a wee bit more gentle in the highs, and punchier. SW51 I wouldn't necessarily call warm.

    Don't have my multimeter (in San Antonio right now), but can infer from Magni vs TA-66 frequency measurements of HD800 and Grado RS1X. Will report back. 5.5 ohms is possible with some feedback.
     
  13. rlow

    rlow A happy woofer

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  14. Nick76

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    In my opinion yes, having both amps and the headphone in at the same time. Just a better pairing, gives it a nice mid bass thickness and punch.
     
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  15. SofaSamuraiX

    SofaSamuraiX Almost "Made"

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    Dammit, I might be a gear junkie....
     
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  16. rlow

    rlow A happy woofer

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    Dude, everyone here is a gear junkie. :punk:
     
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  17. Biodegraded

    Biodegraded Friend

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    Re. TA-66 output impedance:
    If it's on the low side, those 'phones might not have extreme enough impedance vs frequency curves to allow a very close estimate. If you have a pair of Focals on hand - or better still Andromedas or Aras - better to use those instead.
     
    Last edited: Jan 15, 2025
  18. roshambo123

    roshambo123 Friend

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    We had talked about DV having "oily" timbre. It's definitely a very wet presentation
     
  19. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    Isn't PP requiring a transformer on the output? I seem to remember some otl pp's but they were quite rare and exotic.
     
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    SofaSamuraiX Almost "Made"

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    Oh thank goodness! I was worried you all might tease me!
     

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