Review and Measurements of Massdrop THX AAA 789 Amp

[ReAlien]

Biggest issue with low input impedance is decreased volume. As it's still 2k so no concern about distortion or such. My own diy headphone amplifier only has 1k input impedance. Just for the record. And low input impedance also drastically reduces the possibility of interference.

So.
As long as you don't experience volume decrease you are fine. No issue.
But if you experience some issue what i can say is why bother.....
Solutions if you really want to use it:
1 connect input of the new amp to the output of thx.
2 accept it as a attenuator which isn't necessarily a bad thing allowing you better low volume operation range
3 reduce the dac output impedance. 600ohm is indeed really rare, most are 100-200ohm. That depends on how its output is implemented. If it's just resistor you may just change it to 100ohm. Ask people who can help you to do the modification if you like.

Thank you for a detailed reply! So you say that the only real drawback of the combination of low input and high output impedance is a decreased volume? No sound distortions or bass attenuation and such? If so, that's really no bother.

1. I plan to sell THX to finance this DIY amp purchase)
3. I've already found a person to do that, I need to send my DAC to him and he will look into possibilities to reduce DAC's output Ohms.

And this also might not be a problem at all if I decide to buy the DIY DAC from the same engineer, which I am considering since yesterday.

 

[lator]

Better than stock XLR cable? That won't make a difference mate

Don't underestimate before you have experience with stock headphone cable from the likes of Shure or MrSpeakers (before their new Vivo cable). There are stock and then there are stock cables

 

[DeepSpace57]

Don't underestimate before you have experience with stock headphone cable from the likes of Shure or MrSpeakers (before their new Vivo cable). There are stock and then there are stock cables

I have Ether Flow C. THX and Ether Flow C somehow do not like each other in the low-frequency region such as drum kicks etc. I am curious about replacing the stock cable with 4 cores-cable having a pure copper of 20AWG or shorter diameter.

 

[or965]

Hello, I just received the THX 789 but there is weird issue, When I touch the metal case I feel that I get small electric shock, it remind me similar situation, when I charged my laptop in a house with no grounding and touch the metal case, I always got electric shock from it but the power adapter of the THX 789 has no ground pin and I use it in a house that has proper ground .The weird part is when I contact the RCA cable from my topping d50 DAC to the THX 789 I did not get any electric shock from touching the metal case. Is it normal or I got a faulty unit .Also when I touch the right part of the amp it wobble, seems that the feet is not ok .

 

[ZeDestructor]

Hello, I just received the THX 789 but there is weird issue, When I touch the metal case I feel that I get small electric shock, it remind me similar situation, when I charged my laptop in a house with no grounding and touch the metal case, I always got electric shock from it but the power adapter of the THX 789 has no ground pin and I use it in a house that has proper ground .The weird part is when I contact the RCA cable from my topping d50 DAC to the THX 789 I did not get any electric shock from touching the metal case. Is it normal or I got a faulty unit .Also when I touch the right part of the amp it wobble, seems that the feet is not ok .

That's just the ungrounded PSU leading to a very high "zero" potential relative to global earth/ground. you can solve that by replacing the PSU with a grounded PSU, or adding some kind of grounding wire dropping it to global earth potential.

 

[or965]

That's just the ungrounded PSU leading to a very high "zero" potential relative to global earth/ground. you can solve that by replacing the PSU with a grounded PSU, or adding some kind of grounding wire dropping it to global earth potential.

That what I was thinking, but I return it as it wobble on a flat surface after I touch the right side of the amp .I really impressed with the customer service of DROP ,they answer really fast and solve my issue in very short amount of time .

 

[DonMobliano]

Update: I also tested this amp with my LCD-X headphones and I also tried changing the DAC to my RME ADI-2 and the quality on the balanced output was still terrible. As a last ditch effort I ordered a non-Audeze cable from Amazon and it completely fixed the quality issue! I was blown away. The amp now sounds fantastic on the balanced output. I'm really shocked that a brand new Audeze balanced cable was the problem.

For those interested, this is the cable I ended up buying which fixed the quality issue - https://www.amazon.com/dp/B07DD764H8/ref=cm_sw_em_r_mt_dp_U_LO7QDbMK4GG3A

TLDR: I had a bad balanced cable which made the amp sound terrible. Replaced the cable and it sounds great now!

I'll leave my original post below for historical purposes:

So I'm not sure if I should start a new thread for this, but I'm having some issues with this new THX 789 amp I just received. First let me explain my setup and thought process.

I have been running a Topping D70 into a Schiit Lyr 3 with the Treasure Globe 6SN7-SE GF limited edition tube and a pair of Audeze LCD-2 Closed Back headphones. I wanted to try a THX solid state amp with balanced out to headphones, so I picked up the Audeze balanced cable direct from Audeze as well as new in box THX 789 amp from someone on ebay (paid a lot more than MSRP for it too). For an audio source, I'm using qobuz and WASAPI exclusive from my Windows PC over USB.

I received the amp today and plugged it in, first testing the 1/4 SE output. My initial impression was not great in that the warmth, brightness and detail seemed to not be as good as my Lyr setup. I then replaced the cable and went with the balanced cable out to the headphones and the quality took a HUGE dive. Running balanced its hard to describe other than it sounds like the way my old Altec desktop speakers used to sound plugged into my 486dx2 BSD PC back in the early 90's. It sounds like I'm listening through a pop can or something. Absolutely terrible audio quality.

To help troubleshoot, I plugged my Lyr back in and I'm testing the amps side by side where I'm running SE out of the Topping into the Lyr and XLR out in to the THX 789 amp. I went back to the 1/4 TRS cable to make swapping back and forth between the amps easier. I have tested a number of times across a wide range of music and have noticed that the THX amp sounds a lot better than it did initially on the 1/4 TRS SE output and the Lyr3 only sounds slightly better to my ears. I'm thinking maybe there was some warmup time for the caps which has resulted in the SE output to sound better than it did initially, however the balanced output still sounds absolutely horrible.

I'm running the THX on middle gain and about half volume, but have tried it across all three gain settings and different volume levels, but nothing seems to help make the balanced output sound better. I'm hoping I'm just missing something? The most troubling thing for me about this is that the 1/4" SE output sounds so much better than the balanced. I'm using an Emotiva Control Freak as an XLR connection between the DAC and the THX amp. Maybe I need to try the SE input to the amp or a different pair of XLR cables?

Edit: I decided to try running SE out of the Topping into the THX 789 amp and it didn't change anything. After listening some more to the balanced output, I would say that it sounds almost like there is a hall reverb applied, primarily to the mids and highs. This is what I meant by pop can earlier. The soundstage is also more consolidated. Basically it sounds like what I would expect to hear out of some cheap headphones plugged directly into my computer's onboard sound card.

Picture of my setup is attached. Thanks in advance for any help!

 

[RickSanchez]

Back up on Drop for the next 7 days:
https://drop.com/buy/drop-thx-aaa-789-linear-amplifier

No discount, just the regular USD $400.

 

[ReAlien]

1. I plan to sell THX to finance this DIY amp purchase)
3. I've already found a person to do that, I need to send my DAC to him and he will look into possibilities to reduce DAC's output Ohms.

And this also might not be a problem at all if I decide to buy the DIY DAC from the same engineer, which I am considering since yesterday.

Heh, I came to report that it all ended up in me selling THX to finance a purchase of a new DACamp from the same author thus eliminating the impedance matching problem altogether.

This DACamp — S-Audio Focus — is an outstanding device offering quite authentic sound reproduction, which has no peers in the audio world at the moment owing to an unparalleled in-house binaural DSP. I strongly suggest it to anyone looking for a truly neutral/honest sound with 3D soundstage experience (I switch binaural effect off when I use Focus as a DAC-preamp for the speakers' amp).

 

[LuckyLuke575]

I have this idea in my head that I need to buy this amp when I buy a pair of Sennheiser HD 800 S headphones, drop a couple of hundred bucks on a fancy balanced XLR cable, and then hook it up to a nice balanced DAC...

 

[RickSanchez]

This DACamp — S-Audio Focus — is an outstanding device offering quite authentic sound reproduction, which has no peers in the audio world at the moment owing to an unparalleled in-house binaural DSP.

You mean this? http://s-audio.systems/focus/?lang=en

Anyhoo, that's a pretty bold claim considering the recent releases of the Sabaj D5, SMSL M500, and the Topping DX7 Pro. All of those DAC/amp combos measure incredibly well. I think folks here (on ASR) would prefer to wait to see actual measurements of the S-Audio DAC/amp before putting the SOTA designation on it.

And not that there's any correlation, but gives me a bit of pause when I see any DAC using the same case as this guy ...

 

[Hemi-Demon]

Heh, I came to report that it all ended up in me selling THX to finance a purchase of a new DACamp from the same author thus eliminating the impedance matching problem altogether.

This DACamp — S-Audio Focus — is an outstanding device offering quite authentic sound reproduction, which has no peers in the audio world at the moment owing to an unparalleled in-house binaural DSP. I strongly suggest it to anyone looking for a truly neutral/honest sound with 3D soundstage experience (I switch binaural effect off when I use Focus as a DAC-preamp for the speakers' amp).

Where do you buy this DAC? I read the Porta review and now I am curious. Also what is the price?

 

[ReAlien]

You mean this? http://s-audio.systems/focus/?lang=en

Anyhoo, that's a pretty bold claim considering the recent releases of the Sabaj D5, SMSL M500, and the Topping DX7 Pro. All of those DAC/amp combos measure incredibly well. I think folks here (on ASR) would prefer to wait to see actual measurements of the S-Audio DAC/amp before putting the SOTA designation on it.

And not that there's any correlation, but gives me a bit of pause when I see any DAC using the same case as this guy ...

Yes, I mean exactly this one.

You have probably read me wrong, my claim is that it has no peers in terms of its in-house binaural DSP. As to the measurements, I would love to see Amir's review on it. IMHO, this is the best natural and pure sound I have heard in my life but who am I with my limited experience?)

I think it considerably surpasses THX in the authenticity and purity of the sound throughout the entire frequency range, it produces much more emotion yet adds completely nothing to it. Quite critical to the quality of your recordings as it will reveal all inherent problems. With the great records it sounds awesome.

The binaural effect is a thing to hear, it is not like headphones and still not like speakers, something in between, I love it, it is something completely new. Works differently with every record depending on the attention producers paid to the soundstage details. IMHO, especially suits jazz and classical music.

 

[ReAlien]

Where do you buy this DAC? I read the Porta review and now I am curious. Also what is the price?

Directly from Nazar from S-Audio. Write him an email.

The price is 800 USD for a device with no box and no cable. Just Focus and nothing else.

 

[Hemi-Demon]

Directly from Nazar from S-Audio. Write him an email.

The price is 800 USD for a device with no box and no cable. Just Focus and nothing else.

Whoa $800? Yeah thats a bit pricey, without a review. Guess I will wait

Directly from Nazar from S-Audio. Write him an email.

The price is 800 USD for a device with no box and no cable. Just Focus and nothing else.

Would you be willing to pop the top of yours and take a few pics of the internals? Taking a leap of faith at $300-500, is cool, but at $800 thats a pretty big leap based on the website detail.

Also the CM6631A chip is the same one Schiit uses, I wonder how clean the usb input is?

 

[ReAlien]

Whoa $800? Yeah thats a bit pricey, without a review. Guess I will wait


Would you be willing to pop the top of yours and take a few pics of the internals? Taking a leap of faith at $300-500, is cool, but at $800 thats a pretty big leap based on the website detail.

Also the CM6631A chip is the same one Schiit uses, I wonder how clean the usb input is?

Yeah, I've bought it after the extensive 3-day test at home.) I wouldn't spend 800 USD without a listening test. The test piece is still in my city but it will not go abroad, I'm afraid. Though I will try to talk with Nazar about sending one unit to Amir for a review. Maybe he would agree, who knows.

I'm not willing to open my Focus yet, I've just received it.)

If I'm not mistaken Nazar wrote a custom firmware for CM6631A chip to make USB input flawless.

 

[yapst38]

I checked monoprice website, there's stock now for their 887.
Wonder if i should get this and not wait for MD

 

[Veri]

I checked monoprice website, there's stock now for their 887.
Wonder if i should get this and not wait for MD

? Why wait for MD at all. 887 is a hair cleaner measuring & longer warranty. Unless you like the look of the drop one, monoprice is simply more competitive.

 

[RickSanchez]

? Why wait for MD at all. 887 is a hair cleaner measuring & longer warranty. Unless you like the look of the drop one, monoprice is simply more competitive.

+1 on the warranty. The build quality for equipment -- especially newly released equipment -- can be tough to judge. So the warranty period and how the manufacturer handles warranties is really important, and not often discussed when we talk about measurements and features for DACs and amps. From my own personal experience Monoprice customer service has been top notch so their warranty period in particular would carry weight with me.

 

[ReAlien]

Would you be willing to pop the top of yours and take a few pics of the internals?

I have found the photo of the Focus internals on the Nazar's forum: http://www.audio-perfection.com/forum/showthread.php?tid=608