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Review and Measurements of Massdrop THX AAA 789 Amp

jawbfl

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Just to note that a headphone amp can't drive speakers. Only a speaker amp can do that.

But if you mean you want the capability to hook up active pro audio speakers, that is a good reason to go with a balanced setup. Some pro audio speakers (e.g. JBL LSR series) are prone to picking up PC noise when used with unbalanced connections. But with other speaker setups, unlikely to help.

As for the notion of being able to drive almost any headphones, the headphone community always moves to the latest, most powerful amp and hypes it that way, as well as promoting the general sentiment that balanced is the only solution for driving difficult headphones.

Single-ended amps such as the Schiit Heresy come very close in headphone amp performance to the 789. And even the Atom has sufficient power to drive 99% of headphones.

So personally, I would not focus on "balanced" since you are looking at the used market. There are many amps, some of which are not balanced, that can meet your needs for driving future headphones. I would look at everything about an amp.

Yes, sorry I meant as preamp.

I understand "balanced" can be a marketing buzzword and many products implement it badly just to slap "balanced" on the box. I generally follow value, living in a country where minimum wage is the price of a new 789 I have some immunity against hype, even if I can afford it, it makes me feel bad :)

For the ~$100 family of amps I wouldn't get them 2nd hand, and to anyone outside the US they're bad deals because:
- Not a significant drop from MSRP, usually go for $80-90
- Currently JDS and Schiit are only shipping express which is expensive
- Require additional 220V plug because you will only find those offers for 110V, so another shipping bill unless you found a kind seller who would do you the favor of consolidating the packages

So not worth it at all 2nd hand, though $250-300 amps like SMSL SP200 and Drop 789 go for $160-220 and take 240V, that's a nice value IMO.
 

bequietjk

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789 is a wonderful piece of equipment and imo shines brightest utilizing the balanced inputs with a dac.
 

bequietjk

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Oh yeah. To my ears, soundstage width is a bit greater and the noise floor seems to be lower. The soundstage being wider could be a symptom of a lower noise floor with balanced input. The best part of balanced in is that i no longer have to consider high gain for either my HD600, T50rpIII or K712.

@jawbfl
 

jawbfl

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Oh yeah. To my ears, soundstage width is a bit greater and the noise floor seems to be lower. The soundstage being wider could be a symptom of a lower noise floor with balanced input. The best part of balanced in is that i no longer have to consider high gain for either my HD600, T50rpIII or K712.

@jawbfl
Thanks, in theory the signal from DAC to Amp is low so very prune to noise thus balanced inputs should be better, but I don't believe an amp can affect sound stage, as you said might be a side-effect of something else.
As long as RCA can output balanced then it's fine for a temporary setup till I get a decent DAC.
 

zepplock

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Oh yeah. To my ears, soundstage width is a bit greater and the noise floor seems to be lower. The soundstage being wider could be a symptom of a lower noise floor with balanced input. The best part of balanced in is that i no longer have to consider high gain for either my HD600, T50rpIII or K712.

@jawbfl

From charts, it has ~150db noise floor. How can you hear that? Not picking on you or anything, just wondering if I can reproduce it on my setup.
 

JohnYang1997

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From charts, it has ~150db noise floor. How can you hear that? Not picking on you or anything, just wondering if I can reproduce it on my setup.
It's actually the opposite. Balanced output has much higher output noise. The slightly excessive high frequency energy causes illusion of wider sound stage.
 

raistlin65

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From charts, it has ~150db noise floor. How can you hear that? Not picking on you or anything, just wondering if I can reproduce it on my setup.

And here are measurements Amir took with unbalanced input and output. SINAD 118db.
https://www.audiosciencereview.com/...sdrop-thx-aaa-789-amp.5001/page-4#post-111966

Seems highly unlikely there should be an audible difference between single-ended and balanced, unless someone has very difficult to drive headphones and listens very loud and is simply reaching the limits of the amp.
 

JohnYang1997

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Wait a minute. You were talking about inputs. I missed that. In that case maybe you avoided the leakage current mains noise by doing that.
 

bequietjk

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THD and SINAD numbers look great for unbalanced in comparison to balanced input. Could this be because of higher voltage?

The lower frequencies look to be much more tamed and smoothed in balanced input vs that of unbalanced input.
 

raistlin65

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THD and SINAD numbers look great for unbalanced in comparison to balanced input. Could this be because of higher voltage?

The lower frequencies look to be much more tamed and smoothed in balanced input vs that of unbalanced input.

Not sure what you mean. Balanced or single-ended with unbalanced input, the 789 measures so well that any audible differences you find are most likely due to perceptual bias.
 

bequietjk

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@JohnYang1997 Right right. Just wanted to be clear that the topic was in regards to switching between the inputs and not the output.

For a frame of reference my listening chain goes:

PC > Motu M2 (balanced TRS - XLR out) > (balanced input) THX 789 (balanced output) > HD600
 

bequietjk

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@raistlin65 Perhaps :)

I'm only one owner thus can only speak for myself.

I wonder what other 789 owners have experienced.

@jawbfl It is also possible that my Motu M2 balanced output has better measurements than its unbalanced so in this regard, please take my comment with a grain of salt!
 
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zepplock

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I was not referring to SINAD, which is limited by 2nd and 3rd harmonics. I was referring to the noise floor. How can anyone claim they hear the difference of 150db vs 140db or even 120db? And id they still stand behind that claim, how can we verify/debunk it?
 

zepplock

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@raistlin65 Perhaps :)

I'm only one owner thus can only speak for myself.

I wonder what other 789 owners have experienced.

@jawbfl It is also possible that my Motu M2 balanced output has better measurements than its unbalanced so in this regard, please take my comment with a grain of salt!

I have 789 and use it with both inputs with my He560. Those are hungry and with non-balanced input, I have to crank the volume knob up more, but still staying in gain II setting.
 

raistlin65

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@raistlin65 Perhaps :)

I'm only one owner thus can only speak for myself.

I wonder what other 789 owners have experienced.

@jawbfl It is also possible that my Motu M2 balanced output has better measurements than its unbalanced so in this regard, please take my comment with a grain of salt!

I'm waiting on drop to ship mine.

But a main reason I went with the 789 is because Amir's measurements show it to easily be noise and distortion free, regardless of how one uses it.
 

bequietjk

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My bad i didnt consider the performance of my dacs outputs.

What i want to clarify is that i find a difference in sound when using the balanced input vs the unbalanced on the 789, but what must also be considered is the performance of the dac being used as time and time again, not all dacs balanced + unbalanced outputs are created equal.
 

zepplock

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My bad i didnt consider the performance of my dacs outputs.

What i want to clarify is that i find a difference in sound when using the balanced input vs the unbalanced on the 789, but what must also be considered is the performance of the dac being used as time and time again, not all dacs balanced + unbalanced outputs are created equal.

Performance is (in 99% cases) FR, power/clipping/loudness, channel imbalance/crosstalk. You have to consider which one changes when you compare A to B. If for any reason you end up with just "listening" you have to make sure your loudness is normalized. Otherwise it's impossible to compare anything just by listening.

edit: lol lowndness
 

Rottmannash

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My chain is PC via Audirvana > D70 > balanced to THX 789. Typically listen balanced to HP's and the power on gain 1 and gain 2 is very impressive, even with power hungry cans. Have never used gain 3. Have never sent the signal from the DAC to the amp unbalanced so can't speak to that.
 

Azeendeen

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Hey guys, after I turn on my 789 amp, is it normal to hear one click sound followed by the led signal turning on? ONLY 1 click sound. I thought the click was to show it had turned on right. I have been using it fine since early 2019

Because I was on another thread for another amp, the L30. I said both the L30 and THX 789 made one click noise after turning on. I was told clicking noise in amps are bad and could mean they're broken and could lead to headphone damages
 
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