Monoprice Monolith™ THX Amplifier
Michael Piskor 2019

Monoprice Monolith™ THX Amplifier & DAC Review

The Monoprice Monolith™ THX Amplifier is a mid-fi priced THX certified DAC/Amp combo featuring dual AK4493 and up to 2W of power. It is priced at $499.99

Disclaimer: The Monprice Monolith™ THX Amplifier sent to us for this review is a paid-for sample. We thank the team at Monoprice for giving us this opportunity.

To read more about Monoprice products we have reviewed on Headfonics click here.

Monoprice Monolith™ THX Amplifier & DAC
If you love neutrality, this is something you should consider. It has a ton of power via balanced mode and an internal EQ option that can fix problematic treble when the problems do rise up. The imaging factor is pleasantly set up and viable for near-perfect matching with the T1 mark2.
Slide here to add your score on the gear!110 Votes
Reader's Score

Monoprice is a bit of a newcomer in our audiophile world, I am always happy to take a listen to whatever they have on hand. Recently, I was sent a care package that included their Monolith THX so I will be diagnosing and detailing the Monoprice Monolith™ THX Amplifier, designated model number 24459, which sells for $499.

The realm of Amp and DAC products, which happened to also be excellent deals, is a hefty tier to place a product into these days. Let us see how the Monolith THX handles the competition that broods just over the hill out yonder.

Before saying anything, just a shout out to Marcus here at Headfonics for making this review possible. Thanks, buddy! I appreciate it a ton. (Cost me a lot too! – welcome – Editor)

Monoprice Monolith™ THX Amplifier

The Package and Build

Outside of the Monoprice logo and a standard cardboard box, not much else needs to be said. The experience is bare, for the most part, and at the $400-$500, that is just fine for a small amplifier such as this.

A power supply cable is all that is provided. The exterior chassis is made of solid aluminum and offers an LCD display on the front-facing panel. Lately, amps and DAC’s in this price tier seem to get heftier and beefier every time I review something new. This Monolith THX  is an extremely dense feeling. I’d rate the build quality in the excellent tier and something I would absolutely expect of a product with a price tag like this.

As for the LCD, it feels vibrant to my eye, but, very low resolution on the display. Thankfully, I don’t care at all, even on an objective level and the reason why is because of what features are inside that are offered. With that level of detail and fine-tuning potential, I don’t care what the DPI ratio is for the display.

I can say one thing safely, though, and that is I am extremely happy to see a step style volume knob with a gentle clink feel to it. I don’t know if I am spoiled by my Heron 5 Amplifier from Airist Audio and my Hifiman EF6, both of which offer extremely satisfying CLINK’s to each movement of the volume knob, but it feels possible to me. This Monolith has a very soft step feel to it and not a fully gliding and smooth volume shifter.

Monoprice Monolith™ THX Amplifier


The AMP section utilizes a dual THX AAA 788, and side by side with the recent Cavali amp I reviewed, I couldn’t hear a lick of a difference when an external DAC was used two compare the AMP circuits of those two products.

Beyond this, the Monolith offers a single balanced 4 pin XLR output and a standard ¼. Ok, yes, I’ve reached a point in my reviewing, after neigh a decade of such, where I must start asking for a 3.5mm output and not a ¼ only. I don’t want to use an adapter, I hate them, personally. They get lost non-stop, my cats enjoy trying to steal them and hide them in random areas of my home.

I just want a 3.5mm output because, objectively, a lot of us audio nutcases have expensive IEM’s these days. I have some custom CIEM’s that I just want to leave plugged in and not have to worry about my ¼ to 3.5mm adapter. A small gripe, but I don’t see why we can’t have all three instead of just two output types.


On the flip side, you get a USB-B printer style cable output for DAC usage, a standard optical, a coaxial and an AES3. Further, you receive a balanced XLR 3 pin outputs, along with two sets of RCA’s.

Nice! I can have three sources jacked into this bad boy and not have to unplug all my nonsense over and over. That makes me happy and my life as a reviewer just a little easier.

Monoprice Monolith™ THX Amplifier


The USB DAC offered is a dual AKM 4493, which I am not overly fond of in this implementation on a subjective level, but I do regard it as something clinical listeners will enjoy. As a musicality buff myself, I subjectively prefer warmth but I never let that factor into the objective data points of my review. Just because it is clinical, or, just because it is warm, doesn’t equate to lower scoring.

My personal subjective preference never factors into anything at all except that it is important to note that a product could be very clinical and neutral, not suited for musicality enthusiasts. Or, that a product is very warm sounding and not intended for those who want accuracy to the track.

In this case, the Monolith THX 788 is extremely neutral and clinical sounding. Very, very similar to the recently reviewed Cavali Amp from Drop that I had just reviewed.


The Monolith THX 788 offers some fantastic internal EQ options via PEQ and Shelf EQ options that allow you to “tame” certain frequencies that may be bothersome. Let’s face it, very neutral headphones paired with very neutral sources will likely cause some fatigue and annoyance with tracks that are not well recorded or sibilant in nature. Here, you’ll be able to manually adjust and fix the problem if you need to.


The UI itself is just a bit clunky, but it is form-functional and once you mow through menus a few times to memorize what is where you shouldn’t have an issue.

Sometimes, I tend to over cycle past the area I wanted to dive into and then miss it again on the next pass, only to get it right on the third attempt. It gets a bit annoying having to cycle through with the volume dial and the menu button, but it works fine I suppose. I’d prefer a remote for those operations though and at this price, I do kind of expect one.

Monoprice Monolith™ THX Amplifier

Sound Impressions

So, this is a DAC and AMP combo unit, reviewing both individually would make this review way too long, so I am going to try to keep things nice and simple, lightly touch on both via some comparisons and then move forward as quickly as possible.


This, again, is a very neutral sounding DAC, as well as an AMP. The implementation of the 788 is hyper clinical and so is the DAC, clearly intended to be as such through their product description at the very least used as evidence. When dropping in a very neutral DAC, the Monolith here sounds extremely clinical and pure when ran as a pure AMP.

When only the DAC is used and the Monolith is run through an external AMP, the experience is again extremely neutral. It isn’t until I introduced an extremely warm Burson Conductor SL 1793 into the mix, that I got more warmth out of the experience. But, even then, it was still in the realm of neutral for my ear.

That means this product is extremely stubborn with alteration of tonality, but that is a common trait to have with very neutral sounding gear. They don’t play with warm gear very well at all and that is okay and not a problem. You aren’t buying this product for the warmth, you are buying it for purity and precision.

I had a very difficult time getting this product to pair well with anything very warm. However, all my neutral headphones and other products sounded fantastic with it. This is a neutral champ, undoubtedly.


The Monolith 788 offers an extremely pure feeling bass experience, one that would require massive amounts of DSP to alter into the realm of warm feeling. Again, this is a great trait to have for clinical enthusiasts out there.

Liquid and crystalline in physical tactility, the Monolith here pairs exceptionally well with the Sennheiser HD800, especially so in balanced mode. The extra fullness is very appreciated with proper driving power behind it, top that off with the potential to dial-up or down some problem areas via the EQ onboard and you have a great recipe for some truly amazing dynamism.

I would not call this Monolith THX 788 a bass head product, but you can get a bit more if you so desire. The product seems more tuned for treble EQ response than the low end. Meaning, bass response to EQ is just good, treble response to EQ is excellent.

With a lot of neutrality comes a potential for a lot of dynamic impact and strike factor. If the track is hostile, it will be portrayed as such. Wince factor can get very high on this, as it does with very pure sounding and accurate rigs. This isn’t an issue if the track is well recorded and lacking a harsh dynamic kick in the first place.

Monoprice Monolith™ THX Amplifier


The vocal experience is physically placed in a moderately relaxed position. It is what I would consider relaxed and not forward. A/B comparisons with an older HA160 from Burson, for example, and even my Hiby R6 portable player, showcase a much more forward and intimate feel to the midrange placement factor compared to the Monolith.

Again, if you own the HD800, this is a hell of a DAC and AMP for you if you are looking in the $500 and under price tier. The relaxed tendency of the midrange is not a recessive one, merely, just relaxed and enjoyable.

Intimacy and forwardness is found elsewhere, usually not ever in neutral or accurate products to begin with. I think most of the audiophile world knows that already. But, general consumers may not. So, if you want a very forward and intimate feel, this isn’t for you.

In terms of only placement, headphones like the LCD3 and similar vocal-centric headphones are better suited elsewhere. However, the expansive HD800 type headphones with a relaxed midrange are extremely well suited for this Monolith.

As a Pure DAC

As a pure DAC, the experience is increased when suitable AMP’s are paired with it that exceeds what the internals of the Monolith would be capable of. You can do that if you want to run this only as a DAC, you’ll achieve better things.

As A Pure Amp

As a pure AMP, you won’t get much better. My Heron 5 is still my primary home desktop Amp (it has no DAC, just an amp) and I’ve yet to trump it in the warm sounding field. However, I’ve trumped it repeatedly with neutral and purity factor. Raw clarity in some cheaper models, such as this Monolith, seems to be getting more common over time. By that, I mean that cheaper AMP’s are now sounding like yesteryears best.

This Monolith may very well exceed my Heron 5 in both power and raw fidelity. At nearly 6w in balanced mode, that trumps the 4.5 to 5w of the Heron 5 which tends to introduce some noise at that high of a gain level. I hear nothing of that on the Monolith even at a higher gain level via balanced mode. That is awesome.

Monoprice Monolith™ THX Amplifier


The highlight of the Monoprice is without a doubt its responsiveness to treble alteration. Dropping or adding more in results in an audible flare to the experience, one that can be less potent or more potent depending on your preference. Their internal EQ system is set up nicely for this and unlike the low end, the top end will response “more audibly” when you play with the internal EQ system.

Used as a pure DAC, and when paired with an external AMP, the Monoprice Monolith shines as one of the most clinical experiences I’ve heard in a long time. Especially so in the price tier sub $500. When used as a pure AMP and then paired with another company’s DAC, the experience is only something I would operate in balanced mode for. Not many amps out there can rig pair in the $500 tier and do balanced right. This one does, thankfully.

What I mean by this is that the 4 pin XLR option is sublimely clean even on high power, which is something I want to hear more of in this price tier and have not heard much of lately. Usually, with voltage this high (wow, near 6w I am told!) is just crazy quiet on the ground noise potential.

As mentioned, my Heron 5 AMP maxes less than this Monolith and can’t do balanced, to begin with, and I can hear more noise at max volume pot on the Heron 5 vs the quieter nearer to 6w Monolith in balanced mode.


As mentioned, with clinical tonality comes the immense potential for harshness. That is not the fault of the product, it is the fault of the track. What you hear is what you really are going to hear with absurd accuracy.

90% of audio out there is poorly recorded (subjective statement here, that is my opinion) and the remaining 10% of albums and even online podcasts are produced with amazing gear. With that in mind, that smaller percentage sounds so good, that it makes it worth it to avoid the very bad recordings.

Everyone knows that clinical products will sound harsh if the track is harsh. So you need to avoid that and at least try to tame that with the internal EQ. You won’t be altering much but the physical strike factor, so Eqing the treble experience is a lesser evil than bass equalization, in my opinion.

Monoprice Monolith™ THX Amplifier


The Monoprice Monolith THX 788 is just good at imaging overall. Again, coherency these days is what the game is all about and not an expansive sound. What is offered in terms of height, width and depth of field factors are enjoyable enough for pretty much every headphone I own.

I don’t own a pure DAC that exceeds it in spaciousness, but I can safely say the pure AMP’s out there like my Heron 5 absolutely sound noticeably larger, fluffier and more aired out by comparison. For $500 though, this is a combo unit and I don’t expect it to offer huge staging prowess. Especially not with the internal functions this thing already offers.


Coherency is steadily becoming more prevalent in the audiophile DAC and AMP world, which makes me happy when I pair with certain headphones. Of all the headphones I’ve available to test with, the best suited for usage with this Monolith was the Beyerdynamic T1 v2.

The staging is not expansive, but it is very clean. It is not overly physically impacting, but it can be if you demand it to be. It is tonally perfect for this Monolith and both do not respond that much to bass alteration, to begin with, but both respond immensely well to treble fixes via DSP and EQ.

Beyond that, physical space and coherency, the ability to sound correct and not lopsided, or overly lacking in any one area and playing well in every manner possible, is something both products do well. In that regard, the Monolith is a very, very good sounding unit when we are regarding Imaging as a whole.

It is not the most expansive sounding, but it is one of the better dynamically natural-sounding and feeling products I’ve reviewed recently.

Our Verdict

If you love neutrality, this is something you should consider. It has a ton of power via balanced mode and an internal EQ option that can fix problematic treble when the problems do rise up. The imaging factor is pleasantly set up and viable for near-perfect matching with the T1 mark2.

Beyond that, the Monoprice is extremely well built, and both a DAC and AMP combo in one. For $499, this is a great clinical sounding product. In fact, it might be the best overall neutral-sounding combo unit I’ve reviewed in recent years.

Monoprice Monolith™ THX Amplifier Specifications

  • Model 24459
  • Amplifier 2x THX AAA™ 788
  • DAC 2x AKM® AK4493
  • Analog Inputs 1x unbalanced RCA, 1x unbalanced XLR
  • Digital Inputs 1x Optical, 1x Coaxial, 1x AES/EBU, 1x USB
  • Playable Frequency Response 1Hz ~ 40kHz ±0.5dB (96kHz input)
  • Signal-to-Noise Ratio (A-Weighted) > 120dB
  • Dynamic Range > 120dB
  • Total Harmonic Distortion < 0.0005%
  • Crosstalk < 100dB

Total Output Power


Balanced (mW)

Single-Ended (mW)

16Ω   1960 1560
32Ω   3120 1360
150Ω   1160 290
300Ω   580 150
600Ω   290 73
Maximum XLR Input Voltage 5.2 Vrms
XLR Input Impedance 20 kilohms
Maximum RCA Input Voltage 2.6 Vrms
RCA Input Impedance 10 kilohms
Optical Sampling Frequency 96kHz
Maximum Optical Resolution 24 bits
Coaxial Sampling Frequency 192kHz
Maximum Coaxial Resolution 24 bits
AES/EBU Sampling Frequency 192kHz
Maximum AES/EBU Resolution 24 bits
Supported Sampling Rates 32 ~ 192 kHz
Direct Stream Digital™ Support DSD64, DSD128
Input Power 16 VDC, 1.25A
AC Adapter Input Power 100 ~ 240 VAC, 0.5A, 50/60 Hz
Dimensions 8.7″ x 7.8″ x 2.0″

Sharing is caring!