Monoprice/Monolith THX AAA Portable Headphone Amp DAC

Do you or have you owned a THX AAA portable Dac/Amp or have you taken one for a tet drive? What did you think of it? How did you like the DIRAC feature?

I got mine less than a week ago and my first thought was; this thing is a nuclear reactor! It drives The DIRAC, the EQ possiblities, DRC and the build everything is wow… but. When I go out and I grab my portable rig, 95% of the time that will include a pair of IEMs and that’s where I found an issue. There’s a hiss or noise that I don’t hear it with on-ear headphones but with my Westone UM3x (which are nothing fancy or really sensitive) I can hear it, I can’t imagine what you can pickup with the likes of Heir Audio 8.A or Shure SE800.

Is my unit defective or does anyone else noticed this?

I never heard hiss on the test unit I had. Was this with any off the Dirac and EQ fuctions on? Or just straight through?

I’m pretty sure I had no options activated and I know the volume wasn’t crancked up chrazy high but just to make sure, I’ll test it again later today and describe exactly what’s what.

I have the Monolith 788 and they do have some decent floor noise (hissing). This is just how it is. The 788 is only good at running headphones balanced.

I honestly thought it was a very nice amp both SE and Balanced.

1 Like

Both SE and Balanced both sound great. Doing a A/B with both the balanced and SE on my Sendy Avia. The balanced XLR has more power going out of them vs the SE and seems to have more punch to it. Because of the long overcurrent protection time and having to adjust the volume may have something to do with it.

So I fed the dogs, the wife and myself, then made sure they would be busy for the next hour or so, leaving me enough time to mess around with the THX AAA and try different conditions where that hiss comes out. I’m all set, but then… F#*K! It appears someone left it on last time I used it. And I knew it didn’t have an auto off because Zeos told me so in his review.
So, I will now be evaluating the charging time

Pros: He-Man grade power
Cons: No auto power off feature

lol ignore everything i wrote. I was talking about the the Desktop Amp. :upside_down_face:

So I have some head cannon going on with this portable amp. Is it possible to connect this bad boy inline from my mixer to my other headphone amps? I’m looking to get DIRAC and EQ that gets sent through to the amps. I’m basing this on on the fact that the amp has to take an analogue signal in and then convert it back to digital and then back to analogue so that it can mess with the signal. I want to try and make my THX AAA 789 into something close to the Monolith THX AAA 788. Im also curious if the SE passthrough on the 789 would also help to change the sound of my other amps that are in-line with the portable THX amp.

Well, first I must say that I felt very depressed unboxing the THX AAA portable due to the commments and reviews I had read on ASR forum, the jist of which is that this device has a hiss and background noise that’s unbearable, just plugging your headphones is enough to make your ears bleed. I was so excited after watching Zeos review this Dac/Amp that, as happens way too often, I went and ordered mine with joy in my heart. That joy died a bloody death with those comments.

Now, after spending hours with the THX AAA trying various sources and outputs and things like; powering on with earphone plugged in or not and DIRC on while powering or not, etc… etc, I can tell you that, yes, there is a bit of noise present with iems starting fat -5.0dB all the way up to full volume ay +16.0dB. With just the earphone in, there’s nothing, it shows up when you plug in the LINE In or the USB input (tried various interconnects including Fiio L-19 to BTG mini cable). But no hiss, it’s more like the background you hear from a record player but wouldn’t call that a hiss nor would I say it’s audible with music playing. Remember that, what I’m describing is only with IEMs at very high volume, damage your earing volume. With headphones, it’s clean, nohiss no noise.

To dismiss the THX AAA portable because of a noise you can’t really hear in normal listening condition is ridiculous. This is a clean, precise, powerhouse of a device with great features like DIRAC, DRC, a whatever you want EQ. USB C would have been nice, auto-shutdown too and I’m sure I’ll find a couple other kinks in it’s armor (certainly not in it’s build which is like a tank with a little bit of leather) but as of now, this is my go to portable and if I didn’t have a desktop setup, this would do the job
there perfectly too.

but that’s just me…


Hi, it seems like there are only 2 portable THX options available for the time being: Monoprice and Fiio

The Fiio seems much costlier package unless one already has the Q5 or the X7. And I think it also has lower output power than Monoprice. Has someone got its hands on both of them for a compare yet?


You mean other than Zeos? :laughing:


Zeos should have Japanese friends!


No hiss on my end either unit portable (24460), tried just default and played with the EQ , DRC, Dirac but could not hear any hiss. I do not have the IEM’s you have, cannot do apples to apples, all i have for IEM’s are AKG from my note9, a cheap skull candy, TIN T3 and Moondrop Kanas Pro tried all 4 no hiss at all.

Addition: just finished testing on USB on the PC using native chipset port no hiss also.

I’m pleased to hear that. Monoprice are sending me a new unit that should be quiet. Thanks for sharing.

Are you happy with the unit, any complaints?

None at all, love it wish it had balanced but very happy with it.

1 Like

Has anyone tried this portable amp with a pair of Verum 1s? These are on my shortlist of amps to go with the pair that should be arriving in the next couple of weeks.

for all people having problems with very sensitive iems

  • have a look at the ifi ie match (2,5 and 3,5 / single ended and balanced options) or the ifi ear buddy

you can use the ie match with Ultra (-24dB) or High-Gain (-12dB) sensitivity adjustment
no noise - black background - more dynamics and better details…

I wondered if those were snake oil but apparently not, thanx

youre welcome - I am only an ifi fan and enthusiast for mid-/hi-fi