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Massdrop x THX AAA™ 789 Linear Amplifier - Impressions Thread

Discussion in 'Headphone Amps (full-size)' started by XERO1, Mar 1, 2018.
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  1. FunctionalDoc
    That's why my friend I have Glen OTL for tubes and THX for flat as a board solid state sound.
  2. Zachik
    Hey Doc buddy :)
    Yeah... after playing with the Glenn OTL at RMAF 3 weeks ago - I am in the process of ordering one, too!
    For me, the THX is too flat, but I can definitely see a big audience who would love it.
  3. oqvist
    I would have trouble finding that because I am part of the massdrop and subscribed to this thread. This is awesome if mine got the same issue. Nothing say only listening impressions and no build quality impressions is allowed.
    cardeli22 and Alcophone like this.
  4. redria
    Wow, now that would be the perfect combination! You'd definitely have a hard time beating that.
    cardeli22 likes this.
  5. matti55
    I don't have the ADI-2 but am thinking about getting it. Probably gonna try the built-in amp on out of the box but still am thinking about potential pairings. Given the initial impressions you might be right on that one.
  6. seslan
    I wonder how Jotunheim and topping dx7 compare to THX in terms of sound. Can you provide some insight?
    Last edited: Oct 31, 2018
  7. Baten
    Jotunheim is ass, it is rolled off and sounds just "off". In balanced it has okay power, but for the price THX >>> DX7 (it's ok but cheap cinese made) > Jotunheim (noisy and rolled-off).
    cardeli22 and seslan like this.
  8. seslan
    Thanks for the quick reply! I appreciate it.
  9. alpovs
    @Baten, do you have all three of them? That question was for @Alcophone.
  10. Alcophone
    I only use the DX7s as a DAC and preamp. The few times that I tried its headphone amplifier, I found the sound pretty mediocre, but I also never intended to use it for that, so I didn't try for long. Good enough to burn in headphones, though. :)
    With both a DX7s and a Jotunheim handy, I'd use the DX7s as a balanced DAC into the Jotunheim. If the choice is between either a DX7s or a Jotunheim with DAC module, I'd go for the Jotunheim. In comparison with the Gustard H20 (with Sparkos SS3602s) I noticed that the Jotunheim flattened the Yggdrasil's sound stage (with my Ether C Flow - the sound stage with Jotunheim and internal DAC module was plenty big when I tried the Sennheiser HD800). Not a problem with the DX7s as a DAC because there the sound stage seemed flat to begin with (even with the H20). I wish I had a pair of HD800 just for sound stage testing. Still unsurpassed in that area.

    I haven't spent enough time with the THX amp yet to reach a firm conclusion, but I can give you some impressions (that should make someone here very happy!). With a balanced source and balanced headphones, it's doing a fine job. Clean, full, tight sound. Transients still seem slightly rolled off to me, which can be relaxing, but also takes some of the excitement out of certain recordings, especially with guitars. When I used the iFi micro iDSD as a DAC (i.e. single ended), THX as the amp, and using a single ended cable for my Ether C Flow, I was not happy with the sound. The balanced output with the same DAC and headphones was solid. I have to use it more with my other headphones, I did like what it did to my Focal Listen (single ended only), though I mainly use them straight out of my phone, so any proper amp might impress me with them.

    I find it concerning that the THX amp's manual states this:
    That makes proper A/B-ing (with level matching) very tedious at best. It's also very easy to forget. And I can still just barely hear some music playing with the volume all the way down (balanced in, balanced out, medium gain, Ether Flow). Luckily, it has survived all my mishaps so far.
    alpovs and seslan like this.
  11. seslan
    Thank you for the explanation.

    Reasoning behind the power down rule could be an effort to avoid causing any shorts with 1/4 inch plugs. I've heard stories that this happening to people.

    By the way, I apologize to everyone for the typo. "Can you to prove some insight?" What the hell was I thinking? lol
    Last edited: Oct 31, 2018
    cardeli22 and Alcophone like this.
  12. Alcophone
    That I could understand, but XLR does not have that problem, yet it's not called out as unproblematic. I suppose in regular use it's not too big a deal, but still risky given how many amps handle this just fine, and old habits die hard.
    seslan likes this.
  13. oqvist
    Booring shopping question. Just curious if any EU customers got their yet? Seems to be boat shopping from germany?
    cardeli22 likes this.
  14. AndrewM888
    Yes it's no problem to hot plug/unplug 789's XLR-4 headphone cables.

    We recommend pausing the audio whenever plug/unplug 1/4" and 3.5mm TRS since they short T-R or R-S every time a user plugs/unplugs. Due to AAA's miniscule output impedance ~65 mOhms, even a tiny audio signal can cause full current >1A to flow through the short which trips the overcurrent protection, shutting the amp down for a few seconds before auto-rebooting.

    Conventional amps with 1-10 Ohm or higher output impedance don't face this problem. Their output impedance limits the current. But of course, Zout > 1 Ohm isn't optimal for fidelity.
  15. alpovs
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