Review and Measurements of Massdrop THX AAA 789 Amp

[ZeDestructor]

Interesting that there's people here with scratchy pots. I've had mine for almost 2.5 years now (delivered somewhere around December 2019) and the volume pot on mine is still wonderfully smooth.

3+ years with mine now and still thoroughly enjoying it. Have thought about trying something else but why bother?

I feel ya! About the only thing I feel needs improving on the 789 IMO is moving to an internal PSU with a generic IEC C6 or IEC C14 socket rather than an external brick, but until my 789 actually fails or I feel I need a second desktop headphone amp it stays. If/when the 789 does fail, I've pretty much settled on the topping A90 Discrete as the replacement of choice (I love a cool display and it has the performance to match!).

 

[Veri]

Interesting that there's people here with scratchy pots. I've had mine for almost 2.5 years now (delivered somewhere around December 2019) and the volume pot on mine is still wonderfully smooth.

You must live in a wonderfully dust-free environment...

 

[f78fk]

Does anyone know the resistance value of the volume potentiometer on this amplifier? Is it 20K ohms or 50K ohms? I want to replace it with an ALPS potentiometer.
I want to buy the volume potentiometer first, and after the parts arrive, I will use a cutting machine to cut off the old potentiometer and replace it with the new one.
The old pot is completely unusable, and I want to find a new metal pot to replace it.

 

[vaidd]

Does anyone know the resistance value of the volume potentiometer on this amplifier? Is it 20K ohms or 50K ohms? I want to replace it with an ALPS potentiometer.
I want to buy the volume potentiometer first, and after the parts arrive, I will use a cutting machine to cut off the old potentiometer and replace it with the new one.
The old pot is completely unusable, and I want to find a new metal pot to replace it.

SANNI RA5029NS1

 

[ZeDestructor]

You must live in a wonderfully dust-free environment...

The layer of accumulated dust on said 789 suggests otherwise. I mean, we're not talking warehouse of raw lumber, but it's certainly not low-dust either.

Maybe the lube in mine is taking longer to dry out thanks to being a more humid environment? (I live on a tropical island vs the drier typical continental climate)

 

[Rottmannash]

My house is the dustiest I've ever known and mine is perfect as well.

 

[Veri]

Interesting. Well, maybe it really is also climate related. Or luck of the draw, volume pot-wise.

 

[ZeDestructor]

Interesting. Well, maybe it really is also climate related. Or luck of the draw, volume pot-wise.

Not necessarily climate, but I reckon environmental factors play a role.

 

[jdjung]

I also have had mine from October 2021 and never had an issue with noisy pots. Mine's been perfect and I absolutely love it. It's as smooth as butter and noiseless. Noisy pots are pretty easy to clean though, just use contact cleaner. There's tons of Youtube videos that show you how to clean noisy pots (search "cleaning pots with contact cleaner"), I would not replace it without first trying to clean it. I would suggest doing it twice, with one day between cleaning.

 

[Diable]

There's no reason to buy something else.

 

[ZeDestructor]

There's no reason to buy something else.

Eeeh - between the integrated PSU, 12V trigger, and neat display; I'd go Topping A90 Discrete these days. 789/887 are still amazing, but QoL is nice to have on something that will stick around on a desk for years.

 

[Music1969]

This amp and this THX tech is true head-fi classic!

A few manufacturers embraced THX amp tech early on, like SMSL - they still sell THX based amps.

But I believe SMSL is moving to their own design going forward in next headamp, looking at the specs of it from Munich hifi show.

So which companies will still be using THX amp tech going forward? We'll have to see.

I love my SMSL SP400 with THX AAA 888 - and relay based resistor volume control - no pot issues !

And unlike Topping A90D - my SP400 has 47k ohm input impedance. nice!

SMSL SP400 Review (headphone amp)

This is a review and detailed measurements of the SMSL SP400 balanced THX headphone amplifier. It was kindly sent to me by one of their dealers, shenzhenaudio. It costs US $630 from them. The SP400 makes an attempt at luxury with glossy plexiglass top and digital display: As you see, there...

www.audiosciencereview.com

 

[drewdawg999]

I just got this amp used. Unfortunately there was shipping damage and all the RCA jacks were broken. Too bad since I was planning to use my SMSL Sanskrit 10th mkII with it. So I'm forced to borrow my SMSL DO100 from the big rig for my bedroom headphone listening system. I also bought a cheap Chinese XLR cable for my old Hifiman HE400 and got an XLR interconnect for my Hart cable on my Audeze LCD-2. I needed the extra power over my JDS Atom for planars since I'm hooked on PEQ now and the signal is pretty low, and at times I had to dime the Atom to reach barely satisfactory levels.

Anyways, I find this is an awesome amp, sounds so clean and detailed with plenty of bass drive. Going balanced output has worked out well for me, plenty of headroom now, even if I have to go to high gain at times. And on bass heavy tracks, the drivers literally vibrate my head like a subwoofer, a wonderful sensation. There's a happy ending too: claim came through with UPS and I got a partial refund, so total outlay for a balanced input only unit was a whole 40 bucks. Pretty happy about that. (I'm in the process of replacing the RCA jacks which I desoldered and removed, we'll see how that goes.)

 

[marses]

Hi all. Wondering if Im using unbalance connection from dac to this amp and then connect from this amp to heaphone via balance cable, do you still get that balance benefits?

 

[unpluggged]

Hi all. Wondering if Im using unbalance connection from dac to this amp and then connect from this amp to heaphone via balance cable, do you still get that balance benefits?

You will get +6 dB of output voltage to your headphones from differential amplification (the word "balanced" is a misnomer when applied to headphone drive), but you will not get any "benefits" of balanced signal transmission (common-mode interference rejection).

 

[marses]

Thanks @unpluggged .

Lastly, to anyone who has any opinion. Im currenly using JDS The element as an amp to my hd650. Im considering to get this...
Any opinion on this upgrade path?

 

[Antagron]

Someone on Reddit recently told me that the 789 has poor bass and that the Schitt Jotenheim 2 was far superior. Assuming this is as claimed, since the 789 distortion measures very low, would any improvement in bass be due to pleasant distortion? Or some other factor of amplifier design? Or was that, like, his opinion, man...?

 

[AVKS]

Someone on Reddit recently told me that the 789 has poor bass and that the Schitt Jotenheim 2 was far superior. Assuming this is as claimed, since the 789 distortion measures very low, would any improvement in bass be due to pleasant distortion? Or some other factor of amplifier design? Or was that, like, his opinion, man...?

Sure, that could play a role, as could some sort of mental bias toward expecting the Jot to have more bass. That said, I definitely perceive a rounnder and fuller low-end when listening to my Emotiva A-100 vs the THX-789. Might be distortion, might be something else, but either way I prefer that sound with a few of my headphones.

 

[SCG]

When was the last time these were available, I always see a wait list on there site.

 

[zepplock]

There are probably better/cheaper alternatives. I doubt they will do reruns.