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Review and Measurements of Monoprice Portable Amp and DAC with THX

amirm

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#1
This is a review and detailed measurements of Monoprice Portable Headphone amplifier and DAC with "THX AAA" technology. I purchased this earlier in the week for USD $279.99. With tax it came to little over $300.

For those of you who don't know, THX has come up with amplification module with feed forward error correction which serves to lower distortion in amplifiers. My review of Massdrop THX Headphone Amplifier showed it to have exceptional performance, far and above anything I have measured before. So excitement has been built up for the same technology (but not identical part) used in Monoprice version. Here, we are treated to a portable headphone amplifier and DAC all in one.

The Monoprice Monolith THX has a very serious, business-line appearance:

Monoprice Monolith THX Portable DAC and Headphone Amp Reviews.jpg


It is similar to a modern smartphone but much thicker and heavier. It has dual USB sockets as you see, one for charging and one for data access.

There are buttons on the side for selecting menus options. A low resolution display does the job of showing what is going on. It is lacking in style but it is functional and much better than not having one.

The volume control is analog but controls the level digitally as you will see later. Here, I ran into a bug in its implementation. I was testing the unit when I realized the output level was jumping up and down. I looked a the display and it was rapidly switching between 9.5 and 10.0 dB. By chance the level was set between those two steps, causing it to randomly be read as either 9.5 or 10.0. This should be fixed. Fortunately I could not repeat the issue so may require precise positioning of the volume pot to make it happen.

The unit is plug and play and that is how I tested it using USB input. The line-in and Toslink input testing will have to wait for a later installment. As does coverage of a handful of DSP functions such as filters (both shelf and parametric), dynamic range compression and crossfeed. In other words, I am focusing this testing to just a normal USB DAC and headphone amplifier in the interest of getting this review out as fast as possible.

So let's get into measurements and see if this is a groundbreaking portable DAC and amp as its much larger desktop amp was.

Measurements
I used the volume control to roughly get the output to 2 volts as I normally do for dashboard measurements of DACs and this is what I got:
Monoprice Monolith THX Portable DAC and Headphone Amp Measurements.png


Ah shoot! Yes, this is competent performance but SINAD of 105 (signal over noise+distortion) is not state of the art at all. Indeed, it puts the unit solidly in the middle of second tier of many products I have tested recently:
Monoprice Monolith THX Portable DAC and Headphone Amp  SINAD Measurements.png


It falls in the same category of Topping NX4 DSD for example, but that unit retails for just $160 or nearly half the price.

Ignoring distortion and just measuring dynamic range, we get similar performance:

Monoprice Monolith THX Portable DAC and Headphone Amp Dynamic Range Measurements.png


To put this in context at the risk of creating another golden cow as I have done with my SINAD graph :), here is how the last few products with this measurement rank:

Monoprice Monolith THX Portable DAC and Headphone Amp Dynamic Range Table Measurements.png


Let's look at intermodulation distortion:
Monoprice Monolith THX Portable DAC and Headphone Amp IMD Measurements.png


Noise is disappointingly higher in the part of the graph where it dominates (downward sloping). It is worse than recently reviewed Topping DX3Pro for example.

Let's look at noise and jitter:

Monoprice Monolith THX Portable DAC and Headphone Amp jitter Measurements.png


I was unhappy to see that parade of spikes below our test frequency of 12 kHz. It seems to be a constant and shows up in other test such as the spectrum of this 1 kHz tone:

Monoprice Monolith THX Portable DAC and Headphone Amp 1 kHz Measurements.png


As we see, none of it exists in Topping NX4 DSD. This could be from the DSP or the controller running the display. Either way, it should have been better isolated from the sensitive analog output of the DAC/amplifier.

Fortunately linearity is quite good:

Monoprice Monolith THX Portable DAC and Headphone Amp Linearity Measurements.png


Switching to headphone amplifier part (together with DAC), we see a nice low output impedance of 0.7 ohm:

Monoprice Monolith THX Portable DAC and Headphone Amp Output Impedance Measurements.png


Power output at 300 Ohm is rather low in my book:

Monoprice Monolith THX Portable DAC and Headphone Amp Power at 300 Measurements.png


And here is output power at 33 ohm:

Monoprice Monolith THX Portable DAC and Headphone Amp Power at 33 Measurements.png


For a unit with such strong emphasis on its amplification technology (i.e. THX), I would have thought they would push the envelope on power availability. Such is not the case. We have higher noise too until we get to limit of power before clipping.

Channel imbalance is non-existent due to digitization of volume control pot and using that to control gain:
Monoprice Monolith THX Portable DAC and Headphone Amp channel imbalance Measurements.png


Finally for you geak heads, here is the filter characteristics for the default setting:

Monoprice Monolith THX Portable DAC and Headphone White Noise Filter Measurements.png


As an aside, I got a kick out of it rejecting out of band signal better than Chord Mojo whose claim to fame is filtering!

Anyway, we can stop here as the performance characteristics of the unit are quite clear.

Listening Tests
I started my testing Sennheiser HD-650. Unfortunately I was easily able to push the unit into clipping distortion with my standard test tracks. That said, there is nice headroom here with respect to gain allowing me to get pretty loud levels out of my "audiophile tracks" that are recorded at much less than max. There, music performance was fine.

Things improved a lot with Hifiman HE-400i where I had much more power. I could still get into distortion category but overall, it was a more enjoyable experience.

So other than lack of power, not much at issue here audibly.

Conclusions
The Monoprice Monolith THX Portable DAC and headphone review reminds me of the famous line from Voltaire: perfect is the enemy of good. Here, I would paraphrase that to: expectation is enemy of good! I went into this review thinking I would see incredible measurements but that was not the case. What is there is instead good performance with some flaws such as excess noise bleeding in the middle of audio band. No angels sang in my head as I was expecting.

Power is rather anemic and missed opportunity to showcase this amplification technology. There are better choices for less money both for desktop and portable use.

Overall, the Monoprice Monolith THX AAA misses the mark created by the hype and anticipation for the product. On the other hand, it is a fine unit if you don't have high expectations of volume (as I do). Normally I would recommend such a product but on the basis of what we all expected, I am left lukewarm in that regard.

-------------

As always, questions, comments, recommendations, etc. are welcome.

If you like this review, please consider donating funds using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 

amirm

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#3
The topping NX4 DSD is a portable unit. So is Chord Mojo.

The Topping DX3 Pro is also portable but not battery operated. That one is in my new measurements template to provide a reference point of performance. To the extent something doesn't outperform that combo of DAC+amp, it is not groundbreaking. And such is the story with the Monoprice.
 

Veri

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#4
Somewhat disappointing, since the NX4 and Mojo seem to pull it off in portable format (minus the Mojo's vibration weakness I guess?)
 

amirm

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#5
One note here: this unit, together with the last two from Monoprice were delivered to completely different address. Both street and house numbers were one digit off. Monoprice uses some company in California for their delivery service which apparently has not heard of google maps. Fortunately that person who received it knows me and called and told me about the package. And complained fair bit about having to deal with this.

I sent feedback to Monoprice and no response has come back. I know I won't be ordering anything else from Monoprice in the future.
 

Blumlein 88

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#6
Most monoprice gear can also be purchased via Amazon. Maybe that is a better outlet. Price is slightly higher but with free shipping usually it becomes a wash.
 

TimW

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#9
If I’m traveling with my phone as a music source will a external device like this actually improve my listening experience? Assuming I’m using ear buds or fairly normal/easy to drive cans.
Wouldn't it depend on what phone you have? If you have an LG phone with their quad DAC then you wouldn't be getting better performance with the Monoprice unit. I use an external amp with my LG G7 because it gives me more power and a rotary volume control. That improves the listening experience for me.
 

Veri

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#10
@amirm Is this lowering the expectations on the future Monoprice AAA desktop amp/dac for you? Or do you think that one will be SOTA?
Maybe the other features will provide more of a clue, especially the line-in:

The line-in and Toslink input testing will have to wait for a later installment. As does coverage of a handful of DSP functions such as filters (both shelf and parametric), dynamic range compression and crossfeed.
 

mindbomb

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#11
Is there something about a portable dac+amp that inherently lowers performance? This and the chord mojo both failed to excel.
 

Sythrix

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#12
How's the tension on the volume knob? It looks like it would turn easily in a pocket if it's loose. Had to return the Oppo HA-2SE a year or two ago because it would randomly catch the knob while I was walking and blare the living hell out of my ears. :p
 

pwjazz

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#13
If the dsp features work well and are something you need, this doesn't seem like a bad unit.
 
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#14
OKish for the price, but I expected much better performance to be honest.

Seems like the NX4 DSD remains the rival to beat in this category.
 

Jorj

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#15
I'm still hopeful, even though the measurements are not SOTA, that the Dirac Sensaround II is worthwhile.
 

pwjazz

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#16
Wouldn't it depend on what phone you have? If you have an LG phone with their quad DAC then you wouldn't be getting better performance with the Monoprice unit. I use an external amp with my LG G7 because it gives me more power and a rotary volume control. That improves the listening experience for me.
I have an LG V20 and my NX4 definitely provides more juice to high impedance cans like the HD58X, especially in high gain mode.
 

amirm

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#17
@amirm Is this lowering the expectations on the future Monoprice AAA desktop amp/dac for you? Or do you think that one will be SOTA?
Let me say I will be more sober going into the review of that one. :)
 

Veri

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#18
Let me say I will be more sober going into the review of that one. :)
At this point it's starting to look like it won't even release this year, anyway :rolleyes: very sober indeed. Let's hope these delays will be positive on QA/quality... maybe the portable was rushed. Maybe? :D
 

TimW

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#19
I have an LG V20 and my NX4 definitely provides more juice to high impedance cans like the HD58X, especially in high gain mode.
I've got a Fiio A5 double sided taped to the back of a spare case for my phone. When I'm walking around the house with my HD6XX on the volume knob is just within reach at the top of my pocket. What app do you use for music?
IMG_72801.jpg
 

graz_lag

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#20
If I’m traveling with my phone as a music source will a external device like this actually improve my listening experience? Assuming I’m using ear buds or fairly normal/easy to drive cans.
Sure, however your travel experience is much more relaxed in terms of music enjoyment with a DAP.
On a jetliner, you put your phone in airplane mode and you forget it, but most of all, you do not drain it's battery. :eek:
The DAP assures the rest.
A DAP let's you really enjoy the music, there is no Facebook or Instagram or WhatsApp or whatever application distracting you :mad:, voluntary or involuntary, from the enjoyment of music listening.
 
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