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Review and Measurements of Massdrop THX AAA 789 Amp

Dana reed

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View attachment 93444


@amirm, in your "Headphone Amplifier Signal to Noise Ratio at 50 mV" graph, you had shown:

"MassDrop THX AAA 789" achieving 90

and also

"Drop THX AAA 789 Bal" achieving 84

Is the SNR of 90 achieved with single-ended headphone output? If that is the case, does it mean that single-ended headphone output has better performance than balanced headphone output?
It just means the noise floor is lower, probably because there’s way less gain. So if you have really sensitive IEMs, use the SE out, if you have Hifiman HE6, use the balanced
 

raistlin65

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Need help with improving my ignorance at reading Amir's measurements.

SINAD and THD+N measurements in the first chart reflect 5.8V RMS input.

In chart #3 when he measures distortion vs. power at 300 ohms, resulting in 0.15 watts for unbalanced, what voltage is that at? In other words, I want to know if Amir's measurements for unbalanced headphone output in charts #3, 4, & 5 what I would experience with a 2V DAC.

The reason I am asking is that I am considering getting the 789 to replace my Atom. I would like a unit that is a heavier, rather than one that easily moves when I plug and unplug headphones. In that regard, I really miss the heavier Asgard 2 and NFB-11 that I used to own. As well as the unbalanced pass through for connecting to my speaker amp so I don't have to unplug headphones just to listen to the speakers (which have their own volume control).
 

maverickronin

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The reason I am asking is that I am considering getting the 789 to replace my Atom. I would like a unit that is a heavier, rather than one that easily moves when I plug and unplug headphones. In that regard, I really miss the heavier Asgard 2 and NFB-11 that I used to own.
The 789 still slide a bit. I had to put stickier rubber feet on mine.
 

catman

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Need help with improving my ignorance at reading Amir's measurements.

The reason I am asking is that I am considering getting the 789 to replace my Atom.

---- Reply----

The Atom and the 789 are completely different products. The former is outstanding for its price, which is lower than the 789. The latter is great too. I own and enjoy them both.

If it is the lack of physical heft in the Atom that you are concerned about, there is a simple fix -- a stand such as this.. https://www.amazon.com/gp/product/B07TV2N62W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I place both the Atom and the corresponding DAC therein, and find the unit to be as solid as a rock. If you want a solution for less than $ 200, this combo simply can't be beat. If you are willing to spend more, then of course, the world's your oyster.
 

raistlin65

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The Atom and the 789 are completely different products. The former is outstanding for its price, which is lower than the 789. The latter is great too. I own and enjoy them both.

If it is the lack of physical heft in the Atom that you are concerned about, there is a simple fix -- a stand such as this.. https://www.amazon.com/gp/product/B07TV2N62W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I place both the Atom and the corresponding DAC therein, and find the unit to be as solid as a rock. If you want a solution for less than $ 200, this combo simply can't be beat. If you are willing to spend more, then of course, the world's your oyster.
Appreciate the suggestion. But like I said, I miss having a more substantial sized amp like the Asgard 2 and NFB-11 that I used to have. It's a luxury I know, but I want something bigger :)

Anyway, since I'm in the THX 789 review thread, I thought you guys were supposed to talk me into it? :D
 

trl

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In chart #3 when he measures distortion vs. power at 300 ohms, resulting in 0.15 watts for unbalanced, what voltage is that at? In other words, I want to know if Amir's measurements for unbalanced headphone output in charts #3, 4, & 5 what I would experience with a 2V DAC.
6.7 V RMS @ 0.000207% THD+N, that would be an approx. 3.35X amplification of a regular unbalanced DAC that outputs 2 V RMS.
 

Rottmannash

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Appreciate the suggestion. But like I said, I miss having a more substantial sized amp like the Asgard 2 and NFB-11 that I used to have. It's a luxury I know, but I want something bigger :)

Anyway, since I'm in the THX 789 review thread, I thought you guys were supposed to talk me into it? :D
Its reputation should sell you on it. One of the most revered HP amps around. Tons of clean power, 3 gain levels, balanced and RCA ins, very low distortion and it's fairly heavy. That enough?
 

raistlin65

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Its reputation should sell you on it. One of the most revered HP amps around. Tons of clean power, 3 gain levels, balanced and RCA ins, very low distortion and it's fairly heavy. That enough?
I was trying to get a good answer about what Amir's charts represent in single ended mode for a 2V DAC (see my previous post). Instead of buying merely on reputation. ;)
 

RickSanchez

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I was trying to get a good answer about what Amir's charts represent in single ended mode for a 2V DAC (see my previous post). Instead of buying merely on reputation. ;)
I think you should buy it, give it ~200 hours to burn in, and trust your ears because measurements don’t tell the whole story.

/sarcasm
 

raistlin65

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trl

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I was trying to get a good answer about what Amir's charts represent in single ended mode for a 2V DAC (see my previous post). Instead of buying merely on reputation. ;)
I am unable to find the unbalanced input measurements; am I missing anything here?

This headamp is very good, I don't see reasons not to buy it at this price.
 

raistlin65

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I am unable to find the unbalanced input measurements; am I missing anything here?
Charts #3, 4, & 5. Chart 6 lets you know he's moved to also measuring balanced.

This headamp is very good, I don't see reasons not to buy it at this price.
Are those measurements at 2V DAC input, or higher? Then I will know how good the amp is ;)

Typically, I think Amir does tend to take single-ended headphone amp power measurements at 2V. Just trying to verify since the review does not explicitly state that.
 

trl

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They are balanced inputs for sure, but feel free to ask Amir is you think otherwise. Just the output is unbalanced 6.3 mm plug.

Although, I'm not sure we're on the same page here. :) I already answered the voltage for the 300 Ohms graph was 6.7 V RMS, corresponding to 150 mW output power, if that was your question.
 

raistlin65

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They are balanced inputs for sure, but feel free to ask Amir is you think otherwise. Just the output is unbalanced 6.3 mm plug.

Although, I'm not sure we're on the same page here. :) I already answered the voltage for the 300 Ohms graph was 6.7 V RMS, corresponding to 150 mW output power, if that was your question.
Thanks. That's what I'm trying to understand. I can see that that graph #3 is 150 watts at 300 ohms, unbalanced output.

But what's the input voltage? I don't know how to tell what it is from looking at the graph :)
 

Jimbob54

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Thanks. That's what I'm trying to understand. I can see that that graph #3 is 150 watts at 300 ohms, unbalanced output.

But what's the input voltage? I don't know how to tell what it is from looking at the graph :)
I would have thought the input would have been the xlr ins for all tests unless otherwise stated. So the 5 plus volts you mentioned in your initial question.
 

raistlin65

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I would have thought the input would have been the xlr ins for all tests unless otherwise stated. So the 5 plus volts you mentioned in your initial question.
If that's true, it makes me wonder what its single ended output is like when you feed it a standard 2V DAC unbalanced input?

Since I don't need the balanced inputs or balanced output, maybe I should just preorder the Drop THX AAA One?

https://drop.com/buy/drop-thx-aaa-one-linear-amplifier

It's hard for me to imagine that it won't measure well. And I would save myself $100.
 

Jimbob54

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If that's true, it makes me wonder what its single ended output is like when you feed it a standard 2V DAC unbalanced input?

Since I don't need the balanced inputs or balanced output, maybe I should just preorder the Drop THX AAA One?

https://drop.com/buy/drop-thx-aaa-one-linear-amplifier

It's hard for me to imagine that it won't measure well. And I would save myself $100.
I might be being naive, but wouldn't it peak at the gain factor x 2V assuming it didn't hit the limits?
 
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