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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. gtbrown50
    Haven't noticed that...turn it on and off as needed.
  2. Zbell
    Love this amp so far, but does anyone else have an issue where the amp still produces sound when the volume pot is turned all the way down? I can still hear music (albeit at a very low volume) when the pot is turned all the way down, even at the lowest gain setting. I've never had this issue with previous amps, so I'm curious if the volume pot was just installed incorrectly or if this is a common issue.
  3. AndrewM888
    Yes there's a tiny amount of bleed-through in the pot at nil. It's like 83 dB down. One of the unavoidable issue with analog audio.

    DAC volume controls don't face this issue since the DAC can attenuate all the way down to its noise floor.

    If it's still an issue for you, consider toggling the input switch or power switch to completely kill the audio. Or pause the source.
    Last edited: Nov 27, 2018
    Zbell likes this.
  4. Roen
    The amp itself isn't fully differential balanced anyway.

    Any XLR input it gets will be converted to SE within the amp and then converted back to balanced if you use the XLR output.

    You might as well feed RCA into the amp and let the amp do the conversion.

    If you had a DAC with a balanced out into the amp, you'll get a balanced signal in, conversion to single ended internally, then converted to balanced for XLR output.
    Last edited: Nov 27, 2018
    Baten likes this.
  5. AndrewM888
    This isn't a correct analysis of the situation. Differential SE audio is handled properly within the chassis since the negative side isn't corrupted by noise currents. However SE audio on an RCA can be easily corrupted by CM noise current on the RCA shield which, multiplied by shield impedance, gives a noise voltage.
    The OP's RCA to XLR will solve most of these issues by providing a preferred path for CM noise current to flow, leaving the SE negative wire unadulterated.
    See my previous reply to the OP on this issue.
  6. Roen
    Do you have a link to such a cable?
  7. Roen

    I don't see the XLR output?
  8. CoFire
    Seems a silly question given this amps measured performance, but is their a degradation tradeoff by not bring truly balanced throughout the architecture?
  9. Roen
    There's definitely a cost implication.
  10. Roen
    What does Pin 2 connect to?
  11. Roen


    EDIT: What the hell am I doing linking you to something you've already responded to. It's a long Tuesday.
  12. swmtnbiker
    Folks, I'm currently using a Mimby+Massdrop CTH with my Clears and am wondering how this THX amp might pair with my DAC and headphones. Anyone out there using this amp with the Clear? If so how do you like it? I'd love to order the THX 789, but am worried that it's supposedly ultra-revealing sounds might be too much for the ultra-revealing Focal. I'm asking because I searched the thread and couldn't find any mention. Thanks!
    Last edited: Nov 27, 2018
  13. oqvist
    it suits the super ultra-revealing hd800s perfectly for my ears.
  14. swmtnbiker
    Thanks for the feedback!
  15. Malcolm Riverside
    THX 789 works great with my Utopia though I haven’t tried it with the Clear. I think it would be a case of the strong suits of the headphone and the amp complementing each other instead of being too much of a good thing. If you wanted to mitigate that super-revealing nature you might think of getting an NOS dac like something from MHDT Labs as they tend to have a very analog, easy-going sound.
    swmtnbiker likes this.
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