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Review and Measurements of Monoprice Portable Amp and DAC with THX

JJB70

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I think it depends on your phone and how easy your headphones are to drive. I have a Sony Xperia XZ Premium and I find the DAC and headphone out is very good, the headphone output is a bit anaemic but if used with efficient headphones it does reach a satisfactory volume. To be quite honest I find that the sound quality is as near as makes no difference to the Pioneer DAP I have and so I can't see the point of carrying two devices.
 

graz_lag

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I think it depends on your phone and how easy your headphones are to drive. I have a Sony Xperia XZ Premium and I find the DAC and headphone out is very good, the headphone output is a bit anaemic but if used with efficient headphones it does reach a satisfactory volume. To be quite honest I find that the sound quality is as near as makes no difference to the Pioneer DAP I have and so I can't see the point of carrying two devices.

You're exactly right : one and only device to carry is the best, which also explain the success of the multi-tool Swiss army knife ... :)
I also listen music with my Koss Porta Pro played via my Motorola X Pure Edition (XT1575) when I am on a quick bus or train trip or simply do not want to carry the full artillery.
On longer travels, or on jetliners, 'cause the phone (as any other phone) cannot - in a satisfactory manner, drive my B&W P7 and because I know I am going to have a lot of time available for serious music listening, my iBasso DAP + the B&W P7 are mandatory to be taken on ...
 

Jorj

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Now that I use the Cayin, I almost always use two devices when I'm traveling (even short distances), and I never thought that would happen. With the Hiby app, I can control the Cayin from my phone. It's very nice to be able to keep my DAP in the pocket without dealing with the headphone wires on my phone. Even with the Mojo banded to the Cayin, it's a manageable coat-pocket rig (although I lose volume control). I don't bother with the Mojo if I'm using anything other than CIEMs or the HD6xx.

Given that, and that the Monolith is nearly the equal (measurement-wise) of the Mojo, I'm hoping for it to provide a DSP solution to the 'in-your-head' sound of near-field transducers. I know it's possible, both Smyth and JVC have convincing versions, and the Smyth in particular has been reviewed by people whose opinions I trust and they say the sound is a game-changer. Knowing that, it should not be difficult to create a canned HTRF via DSP, and that is what the marketing of the Sensaround tech seems to indicate. I'd actually give up a bit of inaudible distortion to get a more expanded sense of listening space with headphones.
 

Jorj

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I will listen to Dirac but this is no way the same approach as Smyth. That technology both emulates speakers and tracks your head. None of that is here.

Oh, I'm aware that the Smyth packs a much bigger punch, feature-wise, especially with head tracking and room emulation, which means recomputing the HTRF values in real time. I was just thinking a basic, well designed HTRF should get you a sense of space without hurting fidelity, and that is a lot more sophisticated than just a bit of crossfade. Fingers crossed.
 

restorer-john

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...THX has come up with amplification module with feed forward error correction...

Feedforward is as old as the hills. THX didn't come up with it, and certainly are one of the last to use it, but they've somehow managed to come up with an acronym/name (THX AAA) and persuade people it is something special to pay licensing to have it.

I haven't seen a decent explanation on what it exactly is- have you? Just a combo of FF and something else?
 
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amirm

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Feedforward is as old as the hills. THX didn't come up with it, and certainly are one of the last to use it, but they've somehow managed to come up with an acronym/name (THX AAA) and persuade people it is something special to pay licensing to have it.
I am aware of this. I didn't say they invented it. They do have a couple of patents on it though:

Here is one: https://patents.google.com/patent/US8004355B2/en

And the other:
https://patents.google.com/patent/US8421531B2/en

Yes, they read like classic feed forward designs of early 1980s but there may be some twists in the passive mixing stage.
 

JJB70

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Another example that good implementation matters far more than just assembling good components?

On feed forward, that's not new but really there aren't that many genuinely new ideas. I work in heavy engineering and used to do design work and design verification for power plants and ship power and propulsion systems and most of the new wonder ideas in those fields were anything but new.
 
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Deflates my hopes for the desktop version, unless that Dirac Surround is really something worth having.

Guess I will wait for the Massdrop THX amp to drop again and try to figure out what dac to go with it.

There doesn't seem to be any affordable AKM based DACs with XLR out on the market, other than the SDAC balanced which wont be widely available for quite some time. Hopefully someone puts one out in the near future.
 

rajapruk

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Deflates my hopes for the desktop version, unless that Dirac Surround is really something worth having.

Guess I will wait for the Massdrop THX amp to drop again and try to figure out what dac to go with it.

There doesn't seem to be any affordable AKM based DACs with XLR out on the market, other than the SDAC balanced which wont be widely available for quite some time. Hopefully someone puts one out in the near future.

I do not get why Massdrop does not do a matching dac to the THX 789 Amp. The Airist R2R was a joke from their side, I hope. Hopefully something is in the making.
 

helloworld

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Deflates my hopes for the desktop version, unless that Dirac Surround is really something worth having.

Guess I will wait for the Massdrop THX amp to drop again and try to figure out what dac to go with it.

There doesn't seem to be any affordable AKM based DACs with XLR out on the market, other than the SDAC balanced which wont be widely available for quite some time. Hopefully someone puts one out in the near future.
smsl m10?
 

graz_lag

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There doesn't seem to be any affordable AKM based DACs with XLR out on the market.

# Teac UD-503, which I have not retained for my upgrade as it was not seen by any of the Linux distributions I'm used to
# NuPrime DAC-9, which I have not retained either but due to the poor reputation of the French importers, the DAC had a relaxed sound, but not lean or bleached
 

Jorj

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When a product so significantly underperforms its stated specifications (specifically dynamic range and THD), I'd hope that the community takes a minute to pop in to their website and post some comments. Monoprice is actually somewhat responsive, so perhaps we can get them to RMA the devices that fail to meet spec or, better yet, fix the design to ensure it meets specs.

The cynic in me says that they will do some handwaving about test methodologies, or simply revise their marketing materials and refund those purchasers that were misled.

At any rate, the buying community should make a stink about it in a way that gets their attention.
 

WondrousHippo

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Well, it could be that the THX portion is performing flawlessly, and the DAC portion is holding things back, correct?
 

avatar

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Amirm, will you test other dac/amps from Monoprice ? This one is surely disappointing, but i feel like the upcoming desktop version will be better and meet the specs, like the massdrop version.
I am also curious about the older version of their desktop dac/amp(almost exclusively for the amp part), this one: reddit.com/r/headphones/comments/28pae7/monoprice_desktop_amp_review/
it costs 80$ and could easily be purchased on amazon.
 
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amirm

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Amirm, will you test other dac/amps from Monoprice ? This one is surely disappointing, but i feel like the upcoming desktop version will be better and meet the specs, like the massdrop version.
I am also curious about the older version of their desktop dac/amp(almost exclusively for the amp part), this one: reddit.com/r/headphones/comments/28pae7/monoprice_desktop_amp_review/
it costs 80$ and could easily be purchased on amazon.
Believe it or not, I bought that already. It never came but I did not notice until 2-3 months later. I contacted monoprice but they did not even reply.

Fastrack to now where I have ordered two other units from them and both went to the wrong address due to lousy carrier they use. So I suspect someone else has that amp now. :(

Given this, I am not in a mood to buy it again.....
 
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amirm

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OK, I finally got a chance to test Dirac sensaround in the Monoprice THX amp. The effect is very subtle. It adds a small but pleasant sense of air around instruments and vocals. Strangely, it does nothing for taking the sound out of your head. The image stays more or less in your head but balloons a bit. Playing a track with tapping sound in the left ear and activating sensaround, actually pulled that more to the center than the other way around.

They advertise that this is not something that you get tired of which I translate into not being exaggerated. And that, it is.

It is very cumbersome to turn it on and off since it requires going into menu and then selecting it to turn on and off. For something like this, I like to have a button that is always active for instant switching depending on what I am playing.

Fortunately it seems to have a positive effect on everything I have played.

I would say this is a small bonus on this amp/dac.

Would be nice to see this as a plug-in for Roon so that it can be manipulated quicker.
 

AndrewMason

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Hi @amirm

Thank you for the review.

I think the "spurious noise" you've flagged in the 1kHz and 12kHz plots is a non-issue common to all DACs and if so, unfair to point out. It appears to be 16-bit quantization noise as result of not enabling dither on the AP when using 16-bit source. Perhaps you had dither enabled for the other products you compared against, or you used 48 kHz there instead of 44.1 kHz (which would mask the issue since 48 kHz and 1 kHz have lowest common denominator of 1 kHz that would be masked by the test tone, whereas 44.1kHz and 1kHz have 100Hz lowest common denominator which isn't masked by the test tone).

In any case, hopefully you can re-check these two measurements with dither enabled, and if different update your earlier post graphs.

Dither is already baked into redbook CDs, so this noise is non-existent in the real world. And using higher bit depth sources like 20 and 24 bit audio improves the situation.

Please see attached plots comparing Monoprice portable with 16-bit 44.1 kHz source: dithered vs not dithered. Note the quantization noise reduces when dithering is enabled. I've also included a 24-bit 44.1kHz dithered source for reference.

Thanks,
Andrew from THX
 

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  • FFT 1 kHz 44.1k-16bit no dither.PNG
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  • FFT 1 kHz 44.1k-24bit with dither.PNG
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Jorj

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It's good to see you here, @AndrewMason. I just finished up a preliminary review of the Monolith portable THX DAC, and found the level of hiss to be much higher than from ANY of my other sources with the exception of the headphone jack on my Dell Chromebook. Is this something you can comment on? I really found it made my enjoyment of the device impossible with sensitive IEMs and good isolation. It's kind of in-your-face.
 
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