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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. Baten
    Because of flat resulting impedance curve due to its very low impedance output, the frequency response will be much more linear and well-behaved, yes.

    It's the only real flaw of the Aune, too high output impedance which will cause a mismatch with efficient/sensitive headphones like the fostex, like iems.
  2. Oublie
    I'm scared!!

    I've been demoing some new toys specifically Sennheiser HD 600'S and Audioquest Nighthawks and the 789 is intermittently switching off and on the unit itself isn't but the sound switches off and the led goes red for a second then sound comes back and led goes white. I've switched it off for now, it could be the input source causing an issue or maybe its that stupid power button and associated electronics causing the issue. I'll leave it a while and try again.

    In the meantime has anyone else experienced this? BTW the only thing I've done is switched gain for the different headphone impedences and used the xlr or 3.5mm connectors. Volume control hasn't exceeded the 12 o'clock position.
  3. AndrewM888
    Hi Oublie,
    Is this happening only when you plug/unplug the headphone?
    Plugging/unplugging the 3.5mm or 6.35mm TRS will momentarily short the amp, and due to AAA very small output impedance triggers overcurrent protection to invoke for a few seconds.
    If not, please tell us more about the conditions immediately before/during shut down.
    Thanks, Andrew
    maxxevv and Baten like this.
  4. Oublie
    Hi I turn the volume to 0 switch off the unit then swap unplug and replug different headphones before switching the unit back on so there is no live switching I set gain before switching on and adjust volume after the unit is running. No shorting would be possible because of the way I use it this is how I change headphones on all my gear .
  5. Oublie
    The unit is essentially cutting out during playback sound switches of, light goes red, sound comes on light goes white. It may do this a few times then not do it again for a few minutes. It's not high decibel transients I.e. Sudden high demands on the amp causing it as its happening with vocals and dubstep so heavy duty bass and light midrange vocal music.
    Last edited: Nov 20, 2018
  6. Oublie
    OK I've powered everything back up the current rig is

    Computer USB, smsl sanskrit dac, rca out to 789, nighthawks on 3.5mm connection gain on 2 volume at about 10 music variable acoustic e.g. Damien Rice flac and mp3 320. let's see what happens for the next couple of hours.
  7. Oublie
    OK 2hrs Acoustic followed by bassotronics Bass Vibe. Not a hiccup switching to HD 600's xlr output everything else the same except very slight increase in volume control. I'm starting to suspect electronic brainfart :)
  8. Oublie
    Panic over for now!

    No more glitches the amp hasn't missed a beat so far I haven't been able to replicate the issue phew!

    So my technical report is electronic brainfart :)

    Phenomenal amp sound wise it is as good as it gets unless you have the hearing of a dog!

    It's truly a wire with gain technically its the most transparent amp I've ever passed a signal through.

    Build quality wise absolutely fine apart from the power button, it's flimsy, wobbles and I don't trust it to last. When you design v2 of this amp give it a button that goes clunk and changes physical position!

    BTW Audioquest Nighthawks rule but need a little bit of dsp in the form of a high shelf from about 700hz not much maybe a couple of dB. More comfortable than HD 600 by far with some of the best bass control and accuracy I've heard. HD 600 mids are better without eq. But the bass isn't in the same league. So far I think the nighthawks have it. BTW I bought both pairs 2nd hand for almost the same price so both have been run in.
  9. MacMan31
    Well I don't care for IEMs so that is not an issue. But basically the THX 789 is better overall for a wider spectrum of headphones.
    Baten likes this.
  10. MacMan31
    Now I'm concerned about the power button. Is this a known issue on this amp? Are other buttons or knobs affected? Does the headphone jack have a firm connection when plugging in headphones?
  11. CEE TEE Contributor
    Hey MacMan31,
    Power button is fine and working as intended. The button does not stay depressed when on because there is an "auto-sleep" feature and if you do not use the amp for a period of time, it will turn itself off. You can bypass this feature if you like, there is a switch on the back. If you bypass the "auto-sleep", then it will remain on forever.

    If you want to turn your amp back on, just push the button again.

    Please note: If you are checking out the power button when you get it and you press on/off quickly a number of times...there is about a 3-5 second delay built into the circuit to protect the parts from fast power-cycling. This was not communicated at launch and has caused some confusion, we apologize for this. Just to be certain, we have checked some reports and amps in the field, they are all working as intended!

    Thank you all for your interest in this amplifier, we're very pleased that so many of you are already enjoying them and spreading the word. :dt880smile:
    Drop Stay updated on Drop at their sponsor page on Head-Fi.
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    Baten and omniweltall like this.
  12. Oublie
    Here's a suggestion CeeTee bin the autosleep and give it a normal power button the first thing I did when setting up the amp was disable that feature. I have personally never needed or used a sleep function on anything electronic apart from my file server and that's because I can use wake on lan and it's in a server rack in a different part of the house. Most of us sit near our headphone amps from my experience so switching it off is not a great hardship it's not like it's an electricity drinking 200w class a tube amp system!

    I understand when you say it's functioning as you the developers intended I know I've been there with software development and don't get me wrong I absolutely love the amp. On the scale of things it's a pretty minor 'feature' as Microsoft would say but it's literally the only negative thing that I have found with the amp.

    I've just ordered an lps for it - not that it's necessary but I've never liked using wallwarts and at the price you could hardly expect to have one included.

    Thanks for releasing such a fantastic piece of gear just one question when are you coming to Europe? I had to pay over £100 import duty, it was worth it but isn't it time massdrop broadened their geographical horizons I know monoprice have. In many instances it's cheaper for Europeans to import directly from China rather than via massdrop.

    Thanks loving my 789 :)

    P. S. LPS in the same style case? If your sticking with this form factor I would buy one also for my CTH. or make the empty cases available for purchase with no predrilled holes for diyers or case transplants.
    Last edited: Nov 21, 2018
    MacMan31 likes this.
  13. alphanumerix1
    Missed the drop this time hopefully there will be another one soon.
  14. smallcaps
    Think it's a regular product now. I see that the drop is active again...
  15. alpovs
    Baten likes this.
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