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Overview of Massdrop THX AAA 789 Amp

dragonspit4

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Dec 7, 2018
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I finally got my THX AAA 789 from massdrop. I decided to record my experience down before I forget. The THX amp came in a hard cardboard box, with very well packaged hard foam inside to hold the amp. After setting the amp up, the first thing I noticed is that the DC power plug (the connector that connects to the amp) has some downwards play. The plug itself is not loose at all, but you can press it down and it will move. I wonder if every THX amp is like this, or this is a defected unit?
The THX amp came with a very detailed startup guide that explains everything you need to know about the amp (one of the best write guide I ever seen).

The design of THX is quite nice, and I really appreciate the knob that let you switch between three gain level. (usually amps only have 2 gain level)
For the sound of THX amp, I decided to compare it to my Schiit Audio Lyr 3 amp. Keep in mind that Lyr 3 is a hybrid tube amp.

Sound:
Compared to Lyr 3, the sound of THX is very forward and pronounced. Lyr 3 seems to blend everything together. All the individual instruments are blended together to form a smooth sounding music (buttery smooth!). The THX amp is sharper than Lyr 3. It feels like Lyr 3 rounded the corners of every note, where as THX forces you to recognize every note. For THX, every instrument is more easily identifiable, you can effortlessly hear every note. It just feels like the resolution is higher for THX compared to Lyr 3. You can effortlessly hear more stuff (detail) because everything is not blended together like the Lyr 3. The bass of THX is tighter, where as Lyr 3 is looser. It feels like the sound of THX is more defined where as Lyr 3 is more fuzzy comparatively. Lyr 3 feels more grander, with more space in the room, where as THX is closer and the individual notes of the music stand out more. For THX, I can tell the direction of the sound more easily compared to Lyr 3, probably do to the fact that Lyr 3 blends everything together. It feels like THX is more technical and pitch perfect, where as Lyr 3 sacrifice some of this for smoothness. THX is definitely brighter amp comparatively.

The words that I would associate with THX AAA 789's sound would be: high detail, high resolution, pitch-perfect notes that are very well defined.

Honestly, I wonder how much of the sound difference is attributed to the inherent difference between a hybrid tube amp and a solid state amp?
I feel that THX does live up it's name, and is definitely better than my Objective 2 amp in terms of sound. No wonder THX is quickly becoming the best selling amp unit on massdrop.

This once again reinforced the fact that the amp unit in a given audio system does make a noticeable difference in sound. Where as I doubt anyone will hear a difference between two well designed (measured) dac unit.

(Please remember that generally speaking, people like distortion, that's why tube amp exist.)
The above is subjective overview, for objective Review and Measurements of Massdrop THX AAA 789 Amp:
https://www.audiosciencereview.com/...easurements-of-massdrop-thx-aaa-789-amp.5001/
 
Last edited:

Legion1capone

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Nov 17, 2018
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Good write-up! Thank you for this. I've e
Considered both of these amps and appreciate your opinion of the two.
 

TChang

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Any one experience a scratchy noise when the volume knob is turned when there is no music or pause? The noise is similar to my old (30 years old) boombox volume control but not as load, expecially when pair with a high sensitive IEM like my BGVP DMG that I purchased from MASSDROP. The sound can be heard from all 3 outputs but alot louder from the balanced but ot the gain control, hoever. I called Massdrop and they promptly send a replacement, unfortunately it has the same exact issue.
 

Hemi-Demon

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Any one experience a scratchy noise when the volume knob is turned when there is no music or pause? The noise is similar to my old (30 years old) boombox volume control but not as load, expecially when pair with a high sensitive IEM like my BGVP DMG that I purchased from MASSDROP. The sound can be heard from all 3 outputs but alot louder from the balanced but ot the gain control, hoever. I called Massdrop and they promptly send a replacement, unfortunately it has the same exact issue.


Yes that is the cross talk issue with some of the 789s. Just turn the pot up past 10%. You could just sell it, for more than you paid, since they are so rare, if it is bothersome. I used the 789s with campfire iems and had no hissing at all off the balanced output. I have never used the SE output.
 

GeekyBastard

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Jan 27, 2019
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Any one experience a scratchy noise when the volume knob is turned when there is no music or pause? The noise is similar to my old (30 years old) boombox volume control but not as load, expecially when pair with a high sensitive IEM like my BGVP DMG that I purchased from MASSDROP. The sound can be heard from all 3 outputs but alot louder from the balanced but ot the gain control, hoever. I called Massdrop and they promptly send a replacement, unfortunately it has the same exact issue.
They're using ALPS RK09 (Green) pot inside the volume knob to cut some corners, if that's RK27 (Drak Bule) pot, the situation would be so much better, it's sad to see they saved the money on the wrong part.
 
OP
D

dragonspit4

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Dec 7, 2018
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Yes that is the cross talk issue with some of the 789s. Just turn the pot up past 10%. You could just sell it, for more than you paid, since they are so rare, if it is bothersome. I used the 789s with campfire iems and had no hissing at all off the balanced output. I have never used the SE output.
Does this issue for all headphones or iems only?
 

W2S

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Dec 30, 2018
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Nice write up

Just need massdrop to do another drop
 

BigBeard

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Jan 6, 2019
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thanks for the review. I managed to order one in today's drop...hopefully it doesn't really take till May to ship. How long did you wait for yours, in comparison to the state estimated ship date?

One thing about a DAC sounding different...the different between my schiit Bifrost uber and smsl vmv d1 is unreal. Never listened to music this clear and detailed before. Probably a downfall of the schiit dac - poor design.
 

andrew

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They're using ALPS RK09 (Green) pot inside the volume knob to cut some corners, if that's RK27 (Drak Bule) pot, the situation would be so much better, it's sad to see they saved the money on the wrong part.
Does setting volume to 100% and using digital volume control at the (PC-based) source avoid the issue?
 

DuxServit

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The THX789 is worth the wait. Definitely a keeper.
 

BigBeard

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yeah I got the email too. they gave a $10 credit to use on the next purchase (bs credit).

I can't believe we wont see this till the end of June.

What the hell is taking so long. Even if 1 guy made these solo he could have made these amps in the same time frame.
 

Dialectic

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yeah I got the email too. they gave a $10 credit to use on the next purchase (bs credit).

I can't believe we wont see this till the end of June.

What the hell is taking so long. Even if 1 guy made these solo he could have made these amps in the same time frame.
They can take the credit and shove it where the sun don't shine. No more Massdrop purchases for me.
 

amirm

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What the hell is taking so long. Even if 1 guy made these solo he could have made these amps in the same time frame.
Probably long lead time on a part. That is the problem with trying to fund manufacturing with people's money. They won't order the parts until the drop is finished only to then realize the lead time has changed for some parts.
 

BigBeard

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Probably long lead time on a part. That is the problem with trying to fund manufacturing with people's money. They won't order the parts until the drop is finished only to then realize the lead time has changed for some parts.

I doubt this was the case, as once the drop opened, it was sold out in a matter of hours (or less, I don't remember), and they received the money from all us buyers. Either way, the larger issue is not notifying people until the day it was supposed to ship.
 

MRphotography

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I finally got my THX AAA 789 from massdrop. I decided to record my experience down before I forget. The THX amp came in a hard cardboard box, with very well packaged hard foam inside to hold the amp. After setting the amp up, the first thing I noticed is that the DC power plug (the connector that connects to the amp) has some downwards play. The plug itself is not loose at all, but you can press it down and it will move. I wonder if every THX amp is like this, or this is a defected unit?
The THX amp came with a very detailed startup guide that explains everything you need to know about the amp (one of the best write guide I ever seen).

The design of THX is quite nice, and I really appreciate the knob that let you switch between three gain level. (usually amps only have 2 gain level)
For the sound of THX amp, I decided to compare it to my Schiit Audio Lyr 3 amp. Keep in mind that Lyr 3 is a hybrid tube amp.

Sound:
Compared to Lyr 3, the sound of THX is very forward and pronounced. Lyr 3 seems to blend everything together. All the individual instruments are blended together to form a smooth sounding music (buttery smooth!). The THX amp is sharper than Lyr 3. It feels like Lyr 3 rounded the corners of every note, where as THX forces you to recognize every note. For THX, every instrument is more easily identifiable, you can effortlessly hear every note. It just feels like the resolution is higher for THX compared to Lyr 3. You can effortlessly hear more stuff (detail) because everything is not blended together like the Lyr 3. The bass of THX is tighter, where as Lyr 3 is looser. It feels like the sound of THX is more defined where as Lyr 3 is more fuzzy comparatively. Lyr 3 feels more grander, with more space in the room, where as THX is closer and the individual notes of the music stand out more. For THX, I can tell the direction of the sound more easily compared to Lyr 3, probably do to the fact that Lyr 3 blends everything together. It feels like THX is more technical and pitch perfect, where as Lyr 3 sacrifice some of this for smoothness. THX is definitely brighter amp comparatively.

The words that I would associate with THX AAA 789's sound would be: high detail, high resolution, pitch-perfect notes that are very well defined.

Honestly, I wonder how much of the sound difference is attributed to the inherent difference between a hybrid tube amp and a solid state amp?
I feel that THX does live up it's name, and is definitely better than my Objective 2 amp in terms of sound. No wonder THX is quickly becoming the best selling amp unit on massdrop.

This once again reinforced the fact that the amp unit in a given audio system does make a noticeable difference in sound. Where as I doubt anyone will hear a difference between two well designed (measured) dac unit.

(Please remember that generally speaking, people like distortion, that's why tube amp exist.)
The above is subjective overview, for objective Review and Measurements of Massdrop THX AAA 789 Amp:
https://www.audiosciencereview.com/...easurements-of-massdrop-thx-aaa-789-amp.5001/


I am just wondering your thoughts on the Lyr 3 are you still using it after your purchase of the THX amp? I currently have the SMSL 200THX which measures very similar to your THX amp and many of the sound qualities from your description are similar to what I hear from my THX amp. I am wondering as I am also interested in giving a tube amp a try to see I enjoy the listening experience of them. The Lyr 3 seems to be reasonably priced for this. The headphones I use are the Ananda, Elear and the 6XX. Any input would be greatly appreciated and what DAC did you pair with your LYR 3?
 
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