Massdrop x THX AAA™ 789 Linear Amplifier - Impressions Thread
Jul 21, 2018 at 5:02 PM Post #137 of 2,613
Hi All,
Thank you for your interest. We didn't have as many listening samples as we wanted at launch but knew this would be a great amp and loved due to early prototypes and the graphs during development.

I just saw some shots of the amps being built...will get a few off the Pilot Run soon and will send a couple of them out for listening impressions.
We also have some measurement graphs from THX we will post.

I have an earlier build that I keep on my desk. The amp is surprisingly natural-sounding, but not "dry". Dynamic, powerful, and clean.

I think we will re-open the drop next month to sell a few that we will have left from the first production run.
Or, the planning team may open it up for more sales with a later shipping date...please keep an eye out next month!
 
Jul 22, 2018 at 12:58 AM Post #139 of 2,613
Hi All,
Thank you for your interest. We didn't have as many listening samples as we wanted at launch but knew this would be a great amp and loved due to early prototypes and the graphs during development.

I just saw some shots of the amps being built...will get a few off the Pilot Run soon and will send a couple of them out for listening impressions.
We also have some measurement graphs from THX we will post.

I have an earlier build that I keep on my desk. The amp is surprisingly natural-sounding, but not "dry". Dynamic, powerful, and clean.

I think we will re-open the drop next month to sell a few that we will have left from the first production run.
Or, the planning team may open it up for more sales with a later shipping date...please keep an eye out next month!
I can confirm that THX-789 indeed sound natural and clean. Plenty power, too. For purists, or people that love very natural sound with no coloration - this one is worth your consideration!
@CEE TEE - thanks for letting me audition it for a few days :)
Good decision on re-opening the drop to allow more people in.
 
Aug 13, 2018 at 9:36 AM Post #141 of 2,613
The drop is on again. Estimated ship date is Feb 15, 2019. This drop is limited to 480 units.

P.S. The drop says "328 Ever Sold". I came here to read the impressions. How come there is none? Who bought 328 units? Am I missing something? Is there another thread about this amp?

P.P.S. Nevermind. I figured the previous drop hasn't shipped yet. I left my flow of thoughts here in case someone else has the same thoughts.
 
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Aug 14, 2018 at 2:28 AM Post #142 of 2,613
This is extremely tempting... Considering the specs and balanced design, the price isn't that bad.

Are the current drop page description gain options accurate? @CEE TEE
 
Aug 14, 2018 at 7:29 AM Post #143 of 2,613
"
This update is for members who joined the drop in March:
Hi everyone,
The Massdrop x THX AAA™ 789 Linear Amplifier is making its way through production! We also have some important updates to share about the gain specifications.
We worked with THX to adjust the gains for the primary use case of the Audiophile community. Previously, the gains were optimized for variance in source output power. Most Audiophiles typically use 2V DAC sources and wish to drive in-ear monitors or hard-to-drive headphones.
With these slight changes there were some updates to the gain specifications, which we have listed below:
General:
  • Frequency response: + 0.01 dB / - 0.03 dB 20 Hz–20 kHz; + 0.05 dB / - 0.15 dB 10 Hz–50 kHz
Balanced Output:
  • THD: -130 dB, 32 ohms, 1 mW: 0.000032%
  • THD: -130 dB, 32 ohms, 100 mW: 0.000032%
  • THD: -122 dB, 16 ohms, 1 mW: 0.000080%
  • THD: -122 dB, 16 ohms, 100 mW: 0.000080%
  • Gain: 0.66x , 2.0x, 6.6x (-4, +6, +16 dB), selectable via front switch"


Damn. The reason I was interested in this amp was the 24db high gain. Going to have to look elsewhere.
 
Aug 14, 2018 at 9:14 AM Post #144 of 2,613
The reason I'm interested is the negative gain. :p It would make my life much easier...
 
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Aug 14, 2018 at 11:08 AM Post #145 of 2,613
"
This update is for members who joined the drop in March:
Hi everyone,
The Massdrop x THX AAA™ 789 Linear Amplifier is making its way through production! We also have some important updates to share about the gain specifications.
We worked with THX to adjust the gains for the primary use case of the Audiophile community. Previously, the gains were optimized for variance in source output power. Most Audiophiles typically use 2V DAC sources and wish to drive in-ear monitors or hard-to-drive headphones.
With these slight changes there were some updates to the gain specifications, which we have listed below:
General:
  • Frequency response: + 0.01 dB / - 0.03 dB 20 Hz–20 kHz; + 0.05 dB / - 0.15 dB 10 Hz–50 kHz
Balanced Output:
  • THD: -130 dB, 32 ohms, 1 mW: 0.000032%
  • THD: -130 dB, 32 ohms, 100 mW: 0.000032%
  • THD: -122 dB, 16 ohms, 1 mW: 0.000080%
  • THD: -122 dB, 16 ohms, 100 mW: 0.000080%
  • Gain: 0.66x , 2.0x, 6.6x (-4, +6, +16 dB), selectable via front switch"


Damn. The reason I was interested in this amp was the 24db high gain. Going to have to look elsewhere.
Hi UFO. The 789 has tons of gain and will still go nearly to clipping with a 2 V DAC. What's your DAC/source rms voltage? And do you use TRS or XLR-4 headphone connection?
 
Aug 14, 2018 at 11:30 AM Post #147 of 2,613
Hi UFO. The 789 has tons of gain and will still go nearly to clipping with a 2 V DAC. What's your DAC/source rms voltage? And do you use TRS or XLR-4 headphone connection?

With the design optimized for 2V inputs, I presume that is singled ended RCA inputs only. Is the design also based on a max balanced XLR input voltage of 4V?
 
Aug 14, 2018 at 11:50 AM Post #148 of 2,613
With the design optimized for 2V inputs, I presume that is singled ended RCA inputs only. Is the design also based on a max balanced XLR input voltage of 4V?

No, it's a bit different...

In gain = 0dB or -10dB position, to avoid clipping internally the max inputs are 7Vrms for RCA unbal or XLR bal.

In gain = +10dB position, to avoid clipping internally the max inputs are 2.1Vrms for RCA unbal or XLR bal

The architecture treats inputs differentially regardless of unbal or bal. That's why the max Vin remains the same.
 
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Aug 14, 2018 at 11:53 AM Post #149 of 2,613
No...

In gain = 0dB or -10dB position, to avoid clipping internally the max inputs are 7Vrms for RCA unbal or XLR bal.

In gain = +10dB position, to avoid clipping internally the max inputs are 2.1Vrms for RCA unbal or XLR bal

The architecture treats inputs differentially regardless of unbal or bal. That's why the max Vin remains the same.

Thanks for the clarification!
 
Aug 14, 2018 at 12:12 PM Post #150 of 2,613
Exactly. We added the -10dB gain setting because it's awesome for IEMs. It permits a large usable range from the volume pot and a really low noise floor.
That would make things much more practical indeed. Since dedicated PC soundcard line-outs pump out 2V (let alone the headphone amp outs), I have always had trouble with the volume control. Currently I'm using low gain on my AE-5 and have set the volume to 18% and I still have to lower the volume further a lot with volume pot (without vol pot I'd have to stick with single digit numbers). It would be the same story with line-out + O2 1x gain mode. While Sabre DACs have pretty great digital volume control but still, this is not optimal...

Negative gain options are great and I wish those would become more popular.
 

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