Review and Measurements of Massdrop THX AAA 789 Amp

[amirm]

My new favorite. Received it from Massdrop two days after ordering.

Two days? Mine took two days for the tracking number to go live. Now it shows deliver on November 28 th or 12 days after being shipped! I wonder if they are walking it to me instead of using a shipping truck....

Congrats by the way.

 

[pkane]

Two days? Mine took two days for the tracking number to go live. Now it shows deliver on November 28 th or 12 days after being shipped! I wonder if they are walking it to me instead of using a shipping truck....

Congrats by the way.

Hope you get it soon! And thanks for the measurements, Amir — they convinced me to try it, even though I already had two other head amps

 

[westyjeff]

My purchases from the "Drop" have always come sooner than the expected delivery date, if that's any consolation.

 

[Jorj]

Two days? Mine took two days for the tracking number to go live. Now it shows deliver on November 28 th or 12 days after being shipped! I wonder if they are walking it to me instead of using a shipping truck....

Same deal here. Paid extra for expedited shipping, and then they took three days to create a shipping label. After that, it seems to have evaporated from the shipping dock, as FedEx claims to have never taken possession and Massdrop could not be bothered to even start a trace. Long story short, five days later and nobody has any idea where mine went, and I'm not alone, quite a few others are complaining about similar treatment.

Regardless, it'll get here eventually (I hope) and then I get to get off the gear merry-go-round for a few spins and just listen to music and offer sage opinions.

 

[helloworld]

For us living in China, in major cities if we order a product from jd(similar to amazon in us) in the morning, we are going to get the products in the afternoon, if we live in other cities, we are going to get the profuct next day. This time ordering from massdrop makes me remembering the days whe I studied in US 10 years ago. It’s just too slow......

Two days? Mine took two days for the tracking number to go live. Now it shows deliver on November 28 th or 12 days after being shipped! I wonder if they are walking it to me instead of using a shipping truck....

Congrats by the way.

 

[amirm]

We have very fast delivery in US. I can send any package in two days using the post office. The problem is massdrop. They have negotiated some cheap FedEx service that is taking this long to deliver.

With Amazon, you can get a package in a few hours and even in our remote area, next day for many packages.

 

[maxxevv]

We have very fast delivery in US. I can send any package in two days using the post office. The problem is massdrop. They have negotiated some cheap FedEx service that is taking this long to deliver.

With Amazon, you can get a package in a few hours and even in our remote area, next day for many packages.

I can attest to that too.

I used a forwarding office based in Oregon for one of my Massdrop purchases. It took 10days to get from New Jersey to Oregon.
Those guys participating ine RAAM (Race Across America ) cover that distance faster on their bicycles !!!

I have used the same office for some Amazon and Ebay purchases before. Usually items get delivered within 48 hours of shipping.

 

[mi-fu]

I can attest to that too.

I used a forwarding office based in Oregon for one of my Massdrop purchases. It took 10days to get from New Jersey to Oregon.
Those guys participating ine RAAM (Race Across America ) cover that distance faster on their bicycles !!!

I have used the same office for some Amazon and Ebay purchases before. Usually items get delivered within 48 hours of shipping.

Not a big deal. It will take 7 days from their NJ warehouse to New York. I just checked google map. It literally only takes 10 hours to WALK there.

 

[Headphonaholic]

We have very fast delivery in US. I can send any package in two days using the post office. The problem is massdrop. They have negotiated some cheap FedEx service that is taking this long to deliver.

With Amazon, you can get a package in a few hours and even in our remote area, next day for many packages.

Yeah I can confirm that Massdrop is the issue. It generally takes at least 2 days from the time the label is "created" to the time it starts moving.

 

[GGroch]

Yeah I can confirm that Massdrop is the issue. It generally takes at least 2 days from the time the label is "created" to the time it starts moving.

Massdrop is a pretty sophisticated outfit; I would not be surprised if slow shipping even for in stock items is deliberate as it supports their brand story. "Our prices can be lower because we make you wait"....even if there is no technical reason for it. If they had generous return policies and fast ship times their sales pitch might suffer.

 

[or965]

Hello amirm , I just bought the THX 789 and I going to use it with my topping d50 DAC ,which gain is the maximum that I can choose without clipping .Also I understand that the output impedance is 1,so is the amp good for low impedance balanced armature earphones ?

 

[Schackmannen]

Hello amirm , I just bought the THX 789 and I going to use it with my topping d50 DAC ,which gain is the maximum that I can choose without clipping .Also I understand that the output impedance is 1,so is the amp good for low impedance balanced armature earphones ?

You can use any gain you like since the max output from the D50 is 2 Vrms but the THX 789 can handle a maximum of 2.1 Vrms input voltage in it's highest gain.

 

[jsmiller58]

You can use any gain you like since the max output from the D50 is 2 Vrms but the THX 789 can handle a maximum of 2.1 Vrms input voltage in it's highest gain.

Is the same true for the DX7S? I intend to pair my 789 with my DX7S...

Thank you in advance.

 

[Schackmannen]

Is the same true for the DX7S? I intend to pair my 789 with my DX7S...

Thank you in advance.

It's the same if you use the unbalanced output of the DX7S, however if you use the balanced output you can't use the highest gain on the THX 789 to avoid clipping.

 

[jsmiller58]

It's the same if you use the unbalanced output of the DX7S, however if you use the balanced output you can't use the highest gain on the THX 789 to avoid clipping.

Thanks! Yes, will be using the balanced connection between dac and amp, so will keep that it mind.

Did I read somewhere here on ASR that the DX7S output clips above -7DB? If I turn it down by that much (by running in DAC-HP mode) in order to avoid the dac clipping would that lower voltage at the 789 enough to run it at the highest gain setting?

A better form of the question would be how low to set the DX7S output to allow use of high gain setting on 789 and would it be OK to just keep the DX7S at that level for all the 789 gain settings to avoid special DX7S output setting just to use high gain on the 789?

 

[Schackmannen]

Thanks! Yes, will be using the balanced connection between dac and amp, so will keep that it mind.

Did I read somewhere here on ASR that the DX7S output clips above -7DB? If I turn it down by that much (by running in DAC-HP mode) in order to avoid the dac clipping would that lower voltage at the 789 enough to run it at the highest gain setting?

A better form of the question would be how low to set the DX7S output to allow use of high gain setting on 789 and would it be OK to just keep the DX7S at that level for all the 789 gain settings to avoid special DX7S output setting just to use high gain on the 789?

I don't know anything about the DX7S clipping above -7 dBFS but reducing it's output to -7 dBFS would cause the output to drop from 4 Vrms to about 1.8 Vrms (If i did the math correctly) which would prevent the THX 789 from clipping in the highest gain.

 

[amirm]

Hello amirm , I just bought the THX 789 and I going to use it with my topping d50 DAC ,which gain is the maximum that I can choose without clipping .Also I understand that the output impedance is 1,so is the amp good for low impedance balanced armature earphones ?

Good answers were given for the first question. In general, almost all amps clip in their highest gains at max volume. That is why you see the hockey stick in power versus distortion curves. I sweep unbalanced inputs up to 2 volts for those graphs and for balanced, 4 volts.

And yes, I don't expect any material frequency response change due to that 1 ohm output impedance (I later measured it at 0.9 by the way with more solid connections).

 

[derp1n]

Did I read somewhere here on ASR that the DX7S output clips above -7DB?

It doesn't.

A better form of the question would be how low to set the DX7S output to allow use of high gain setting on 789 and would it be OK to just keep the DX7S at that level for all the 789 gain settings to avoid special DX7S output setting just to use high gain on the 789?

The general rule is -3dB is half power, -6dB is half voltage, and -10dB is half loudness, although the last is debatable due to psychoacoustics. So -6 dB FS will get you right on 2.0 Vrms.

 

[jsmiller58]

It doesn't.


The general rule is -3dB is half power, -6dB is half voltage, and -10dB is half loudness, although the last is debatable due to psychoacoustics. So -6 dB FS will get you right on 2.0 Vrms.

Thanks! Will run the DX7S at -6dB FS.

 

[TheBatman_Yo]

Hi all, I've been enjoying my 789 for a little while now and decided to do a few tests on my unit. One thing I found is a strange rise in crosstalk vs. frequency when the gain is set to its lowest position (1). Here's a screenshot of what I'm seeing:

View attachment 17717

For gains 2 and 3, crosstalk is practically identical to the soundcard's loopback as expected, but for gain 1, it rises steadily above ~100 Hz. Note that these tests were done unloaded for the best possible results.

Here's my measurement setup:

• Lynx Studio E44 soundcard (balanced output/input) at 96 kHz, 24 bit
• THX AAA 789 (3.5mm SE output -> 3.5mm to RCA adapter -> RCA to XLR cables wired as per LynxTWO manual)
  • Results are identical with the 1/4" SE output
• Volume set to maximum for all tests except for the test at gain 1 (volume set to ~4 o'clock to reach 6 dBV/2 Vrms)
• RightMark Audio Analyzer 6.4.5 software

Other than crosstalk, all other unloaded measurements (frequency response, noise, THD, IMD, etc.) match the soundcard's loopback at all gain settings.

@amirm / @AndrewMason , can you see if you're able to replicate this? I find it interesting that this only happens at the lowest gain setting, and since I use that setting for normal listening I'm a tiny bit disappointed that it doesn't perform quite as well in this aspect, but of course with a single-ended headphone load this is probably inaudible. I don't have the connectors to build an XLR-4 to dual XLR-3 adapter right now, but it'd also be interesting to see if this rise in crosstalk at gain 1 also happens with the balanced output.

Sooo is there any more info on this issue yet? Or did I miss it?