Audinst HUD-mini

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Me: I am a 21 year old Engineering student living in a small town in India. I would like to call myself a music enthusiast, rather than an audiophile. I was inspired by music since childhood, and as the time passed, the passion of music grew in me, and that subsequently led me to join Head-Fi. Eventually, I found the pleasure of listening to music mainly by the HD600 and recently, by the seductive LCD2 headphones, and realized the true components of recorded music. I usually like to listen to Indian Classical Music along with Bollywood songs. My main listening genres include classical, vocal, instrumental, jazz and sometimes pop.
 
Intro:  Audinst, is a renowned Korean headphone amplifier manufacturer. They are based in Incheon, South Korea. The brand was established in 2009. All their products are made in Korea.
 

 
Specifications of HUD-Mini as per Audinst:
 
Interface: USB 1.1/2.0  SNR: 113dB
 
Sampling Rate: 16/24 Bits 44.1/48/88.2/96 KHZ
 
Output: 6.5mm/3.5mm headphone Jack,
RCA Line out & Optical out
 
Headphone Impedance: 16-300 Ohms
 
Weight: 160 grams
 

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Let us see what the HUD-Mini has got for us,
 
Packaging and Accessories: The HUD-Mini arrives packed inside a large colourful cardboard box (typical Audinst Style), on which features and other information have been mentioned upon. Once the box is opened, the main unit and all accessories are put in a foam packaging.  Accessories are found beneath a pseudo-bottom compartment. No complaints here. Nothing special to mention about either; all accessories have a good quality, build and feel to them.
 

 
List of accessories in the box, which include the following: 
 

 
USB Cable: Standard black coloured USB A to B cable, 1.5 metres long.
 
RCA Cable:  Audio cable for Line out function, about 1.5 metres long.
 
Rubber Feet: For attaching to bottom surface of HUD-Mini, thus making it scratch and skid resistant.
 
User Manual: Detailed and informative Instructions about operation, also contains warranty information.
 

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Design and Build: The HUD-Mini has a very good overall build quality.
 

 
The outer case is made up of aluminium, and is painted in greyish silver. Front panel is black coloured; volume knob is rubberized, and has a grippy feel to it. In pictures HUD-Mini looks larger, but in real, it is quite compact in size.
 
On the front side, we have Volume control knob, an output toggle switch (between headphone out and Line out) and an output headphone jack is present in both 6.5mm & 3.5mm format. An active colour changing LED indicator shows the status of operation.  The LED turns green once songs/signal start playing from the source, and stays orange incase there is no signal incoming. On the rear side, we have USB input port, RCA Line-out jacks & Optical output port.
 
 Speaking of Internals, HUD-Mini has a double sided PCB with no wirings. All components used are of premium brands; including all dale resistors, Alps pot, premium caps. The HUD-Mini employs a 24/96 VIA Chip (which obviously has 88.2 support over the popular Tenor’s) There is only one user replaceable part on board the HUD-Mini: The DAC output Op-Amp (which is by default LME49860 in DIP8 format) other op-amp is AD8397 but it is permanently mounted on PCB. Audinst has always been a strong contender in the field of Build, interiors, components and PCB. The HUD-Mini stays & operates very cool no matter what.
 

 
The HUD-Mini is powered solely off the 5V USB line. This makes it also to work straight off an android smartphone, which is a definite advantage for travellers. The HUD Mini also has Line out for speakers or external amps, which again works quite well with crisp and clear output. But the volume control will no longer function when line-output is selected.
 

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Sound:  I feel the HUD-Mini is neutral, detailed and accurate in sonic presentation. Sound-stage width is moderate. Depth is pretty good. Absolutely zero audible hiss/noise. No channel imbalance, and zero EMI pickup & pops.
 
Lows are strong and accurate and go fairly deep. Infact, Mids natural and clear, slightly intimate if I must say; Highs are clean, airy and non grainy, just right amount of sparkle to keep the music alive.
 
Soundstage on HUD-Mini is very good, and realistic and to some extent, lacking in width. Depth is fair. HUD-Mini does not give a fully circular imaging, instead gives out an elliptical stage (with comparatively more depth and lesser width) Detail retrieval, and dynamics are decent enough. Overall the sonic presentation is very much neutral. Also, the final sound impressions of HUD-Mini can be manipulated by using different op-amps.  I have changed to Op-Amps and I could observe that the current op-amp (LME49860) does a very fine job, and I feel there is no need for op-amp rolling to increase sound quality. But the HUD-Mini scales very well with any op-amp installed.
 
As per my observations & comparisons, The HUD-Mini is going to be the most ‘clear & neutral’ sounding amp/dac from Audisnt. Its higher end counterpart MX-1/2 did not quite please me, owing to their dark-sound character.
 
Comparison: The only competitor for the HUD-Mini is its fellow Koran amp/dac: Audiotrak’s Prodigy Cube (99$), which too has very similar functions, features and circuit design. But the Cube will have slight edge & advantage over the HUD-Mini in terms of features (Coaxial and microphone support) but in terms of sound quality, both are neck-to-neck, with Cube providing a slightly warm, smooth and laidback sound character, and HUD-Mini providing a little more upfront and clear signature.

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Conclusion:  HUD-Mini is a great sounding portable amp/dac in its price point, Infact, the sonic performance is the best one can get in sub 150$ portable amp/dac’s. This device is actually pretty great on features and practical aspects. At the price point of 120$ shipped, HUD-Mini stands as best option for travellers with smartphones or laptops.  I can recommend HUD-Mini for any music enthusiast who wants a handsome portable USB amp/dac to drive low impedance headphones.
 
The Pros: 
 
1) Design and Build: HUD-Mini has very well designed and implemented build. It can run off 5V source, eliminating the use for a separate power supply. The HUD-Mini can also run directly on android smartphones. It is also very compact, with practical features.
 
2) Sound quality: The sonic presentation on this little unit is neutral and vastly uncoloured. Default op-amps LME49860 & AD8397 perform very well, I can imagine it would pair well with almost any headphones.
 
3) Value: The HUD-Mini unit carries a great price to performance factor, which is hard to beat in this price range. Perhaps the HUD-Mini is the best portable amp/dac in this price range.
 
 
The Cons: 
 
1) Fixed Volume in Line-Out: Alright, so this is not really a flaw, but it would have been perfect if the HUD-Mini had volume control working even under Line-out mode. Thats it, apart from this I am unable to find any drawback or flaws.

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I am new to headfi and i apologise if review is not very helpful.
 
This entry level dac-amp is quiet a deal from audinst.
 
Disclaimer: I am currently building my rig and have only entry level models, Sennheiser HD448, Audio Technica WS55 to evaluate this amp. I will update this review after using much better cans with it (will probably start a thread as am confused).
 
As one might expect, entry level cans sound almost same regardless source quality. As I found out, this is simply not the case with HD448 and ATH WS55 that I mentioned above. Am using lossless from my laptop to this amp via USB.
 
I would rather not comment on its sound signature as this is my first amp, but I believe all frequencies have received considerable boost is sound quality. Bass is tight and well defined, treble has sparkle and detail, mids are rounded and lush. All this in comparison with my on board sound card and sony discman. All instruments are better separated and are individually well defined.
 
Overall I urge you to try this product if you are using onboard sound or portable device to drive your cans. Its affordable and brings enough to the table so that you can never go back to those sources.
 
One con I would like to mention in comparison to my on board sound card is, it does not sound very open. Instruments are well separated but overall soundstage seems narrow. Will update review with more use.

I just finished writing about the HUD-Mini for my blog, I will paste it in here for easier viewing. Enjoy
 
 
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[size=medium] The HUD-Mini is Audinst's second ever combined DAC & headphone amplifier. The relatively new Korean company may be unheard of in traditional hifi circles but for afordable USB audio their first ever DAC/amp (the HUD-MX1) has made quite an impression. [/size]
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As the name suggests this new model is smaller than their first. Apart from the size the main external change is the lack of a mains power connection. Internally the DAC chip has been changed to the PCM1791a (the HUD-MX1 used the Wolfson WM8740). Compared to the HUD-MX1 the Mini's price is nearly 30% less (£82, compared to £115), but it retains both the small & large headphone connections as well as the RCA line-outputs. With a very low THD+N distortion value of 0.00003% the Mini seems like a refinement of the HUD-MX1's specification. So does it all square up to make the HUD-Mini better value for money, or is it just a cheaper alternative?[/size]
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    SOUND[/size]
[size=medium] Like the HUD-MX1, the HUD-Mini sounds nicely neutral and transparent for their price. Compared to a PCs on-board sound every element of audio quality is improved with the HUD-Mini. The bass is more powerful without becoming boomy or flabby, the detail throughout the frequencies is tighter and more focused. The midrange / vocals get more clear and musical, without feeling overly forward (louder). Treble is well Controlled, but perhaps lacks a little sparkle compared to some of the competition. The soundstage gets wider and deeper making music feel more three dimensional. Volume wise there is not a lot available here, it obviously can't compete with a mains powered DAC/amp, but in the volume department this is by far the least capable, even of all the other USB powered options that I've tried. My laptop managed to get louder at 50% volume compared to the HUD-Mini @ 100%. Plugging in the 600 ohm Beyerdynamic DT880 produced modest volumes for most music (not Classical) with the HUD-Mini at maximum, as long as the surroundings are quiet. [/size]
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After reading Mike's review of the HUD-Mini, on Headfonia.com, I decided to try a couple of different op-amps in the Audinst HUD-Mini*. The above sound impression is with the default LME49860 op-amp installed (out-of-the-box). Here are my impressions of the Audinst HUD-Mini with two different op-amps installed...[/size]
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    SOUND: (OPA2227p op-amp) - £5.90[/size]
[size=medium] I noticed a small change here, the sound seemed to open up a touch (better soundstage). The bass got a little nicer too but this was slight and the problem with comparing here is that you can't do it too quickly. After unplugging the USB, switching the chips, restarting your software and then listening to the same track again you tend to forget the little details. I also liked to put the chassis back together again before listening too, but maybe I'm crazy.[/size]
[size=medium] Unlike others, who have commented on this op-amp switch, I didn't notice any change in volume between this and the default one.[/size]
[size=medium] NOTE: You can now buy the HUD-Mini directly from Audinst (eBay) with the OPA2227p already installed here and only for a couple of £ more, that's nice! [/size]
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[size=medium]     SOUND: (OPA2111KPG4 op-amp) - £10.60[/size]
[size=medium] This op-amp is described as a 'Dual Low-Noise DIFET**' whereas the OPA2227p was a 'High Precision Low Noise'. Make of that what you will, but I noticed a bigger change here than with the OPA2227p. As well as the soundstage opening up a bit more I found the midrange to get a bit brighter / more forward. The bass got more plump and the treble gained a healthy sparkle. Generally this was my favourite presentation of the three. It seemed to give the biggest improvement to Electronic, Metal and anything with strong vocals. The volume also improved with this op-amp, enough so that even the 600 ohm Beyerdynamic DT880 became usable. Classical music was also capable of acceptable volume, as long as background noise was fairly minimal and the HUD-Mini's volume is near, or at, maximum. These are open back headphones after all (OK so technically they're semi-open but really they sound more open than closed). I still advise caution with tough to drive headphones though, I would not describe the maximum volume as 'loud' here, even with this op-amp, and there are people who prefer higher volume levels than I do.[/size]
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** DIFET = Dielectrically-Isolated Field Effect Transistor (just in case you're curious, I was )[/size]
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    MUSIC[/size]
[size=medium] Previously I've avoided talking about specific music tracks in the DAC and amplifier reviews. I was worried that it would get confusing, but I'm going back on this as I feel it will help better describe certain sound characteristics. [/size]
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1. Tony Bennett: "I Left My Heart in San Francisco" - This has an enjoyable vibrancy to the mix of vocals and piano. Tony's vocals come through clean, crisp and well rendered. The soundstage is a bit flat. With the OPA2111KPG4 op-amp the mid-tones feel more forward but also a little sharp / lack a little smoothness.
2. The Crystal Method: "Born Too Slow" - Feels lively from the get-go. Like before the vocals feel clean and well defined, but with more going on here it's even more impressive that they still hold up through all the punchy electronic elements. 
3. Deftones: "My Own Summer" - I quite like how the guitar sounds grainy and quite forward here. Again this is mostly true of the OPA2111KPG4 op-amp, it also feels like it's making the presentation faster. There isn't an abundance of authority here, but clarity, detail and midtones are all quite impressive.
4. Mozart:  "Clarinet Concerto in A, K.622 - 2. Adagio" - This performance felt very engaging. The delicate notes from the clarinet feel solid and smoothly presented. When the strings come in there is a nice feeling of space between the instruments.
5. Ramin Djawadi: Medal of Honor "Watch Your Corners" - This track starts with some nicely presented soundstage elements. There is a nice slam and texture from the low frequencies throughout the track that does well to immerse you into the action. The HUD-Mini also does well not to get too congested and overwhelmed towards the end of the track when the full orchestra comes in hard. 
6. Black Sun Empire, SPL: "Wasteland" -  I was a little disappointed by a slightly flat feeling from the few opening instruments, but when the everything kicks off thing gets a bit more exciting. It impresses with punchy bass and quite a dynamic sense of depth.

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[/size] [size=medium] I own most of these songs on CD, they are ripped as lossless files and played on a PC. The audio is output through a generic USB cable, using WASAPI - event style on JRiver's MC17 - buffering from the RAM. I also chose these songs because they're on Spotify, so if you have a premium subscription you should be able to find them easily and check them out for yourself in decent quality.[/size]
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    COMPARISONS[/size]
[size=medium] The Fiio E17 shares a similar footprint to the HUD-Mini. At £100 the Fiio is a little bit more expensive, but can be bought in Europe. Ordering the Audinst directly from Korea is highly likely to bring you a customs charge which will most likely bring it over the price of the Fiio so for now I will say the prices are roughly equal for arguments sake.[/size]
[size=medium] The feature sets for these two units are quite different. The Fiio E17 has a S/PDIF digital input that takes 24bit/192khz and a battery for using the amplifier only so makes more sense if you want to boost the sound from an iPod too. Lastly the Fiio E17 has bass, treble and gain control, changed via it's on-screen display. I don't put a lot of stock in the bass and treble manipulation but the three levels of gain make the Fiio E17 a better option if you have hard to drive headphones. The Audinst has a nice analogue volume control, a S/PDIF digital output (a bit niche perhaps) and RCA outputs. The latter of which make it easy for connecting the DAC up to an external amplifier and speakers. [/size]
[size=medium] Sound wise I found the Audinst to outperform the Fiio E17, this was reasonably noticeable even with the default op-amp, with either of the other two op-amps it gets better still so if it's purely sound quality you are after here is where my recommendation would be.[/size]
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The HUD-MX1 has a bit more sparkle, a greater presence and a more impressive soundstage. If you are willing to change the op-amp in the HUD-Mini then the audio quality will improve but it won't do miracles. The OPA2111KPG4 gets the closest to the quality of the HUD-MX1. The HUD-Mini makes a great budget alternative to the HUD-MX1 whichever way you slice it.[/size]
[size=medium] Feature wise the two Audinst DACs are similar. The HUD-Mini cannot be mains powered. It also lacks the gain control from the original model so it's not a great option for demanding headphones (300-600 ohms are mostly out). Also note that the RCA line-outputs of the HUD-MX1 are controlled via the volume dial whereas the ones on the HUD-Mini's are fixed. If you have active speakers with no volume (or volume controls on the back) then the HUD-Mini is not so useful.[/size]
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    BUILD[/size]
[size=medium] The chassis quality is not going to give Fiio anything to worry about but the strength and design are respectably solid, simple and clean (especially on the inside). I really appreciate the analogue volume control over buttons here. The dial is almost identical to the one found on the HUD-MX1, which is a precise feeling, rubber coated dial with an nice 'Alps' potentiometer at the core. [/size]
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I really like not having to use adapters when I use headphones, especially with the larger (6.35mm / 1/4"), so I prefer it when amps use the larger connection. Admittedly most headphones use the smaller one, its much easier to convert up rather than down. No need to worry either way here as both sizes are included natively. If only more of the competition followed Audinst's example.[/size]
[size=medium] The S/PDIF digital output here seems a bit superfluous. I can't imagine many people buying the HUD-Mini, only to avoid using it's DAC and headphone amplifier just to pass-through the digital signal to another format. It's useful if you have an older DAC that doesn't have USB sure, but there are loads of cheaper & better options for this. An alternative digital input would have made more sense to me but then they would have to put the mains power option back in, or included batteries like the Fiio E17. [/size]
[size=medium] The RCA outputs are a very welcome addition for anyone with desktop speakers or an integrated amplifier and a desire to connect it to a computer. I plug these straight into my AE desktop speakers and it brings a nice boost to their sound quality too. Audinst even include a basic pair of interconnects in the box to get you started too, brilliant! [/size]
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* Taking the chassis apart is very easy, which is great because of the op-amp switching (mentioned above). There is only one op-amp in the HUD-Mini to play with so it's not going to break the bank, or take long. If you want to experiment here are some instructions:[/size]
[size=medium] Remove all four screws (2 front & 2 back), the back panel will fall off but the front one will not. The easiest thing to do then is - grab the front panel and slide out the PCB (Printed Circuit Board). Once out a little way you'll be able to hold the PCB by it's sides and pull it right out.[/size]
[size=medium] You will probably want an IEC Extraction Tool for pulling out the op-amp, otherwise it's a bit tough to remove. The pressure needed to remove & install the op-amp barely flexes the PCB as it's pretty thick. This operation feels pretty low risk, this was my first attempt and it wasn't too scary.[/size]
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[size=medium] OK one other thing I have to mention... The indicator light on the HUD-MX1 was 'orange' when plugged in and 'green' when playing something, this was fine. The HUD-Mini however flashes between both colours continuously when playing. Apart from being a bit distracting it doesn't interfere with the user experience, but what hell is this about?[/size]
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    FINAL WORDS[/size]
[size=medium] The HUD-Mini is a great performer, giving a substantial audio quality boost to a computer's on-board sound. With great connectivity (both inputs & outputs) and a small & light chassis it makes a great companion for a laptop too. Both of the Audinst DAC/amps are a good buy for their respective prices but with a bit more to spend they soon work their way off the top of my recommended list. For around £150 things get a lot more interesting, but lets be more sensible for a second...[/size]
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The HUD-Mini betters the already impressive Fiio E17 on sound quality. It might end up costing less too (depending on customs). If you can live without the Fiio E17's other features then the Audinst is a clear winner. Comparing the HUD-Mini to it's bigger (and older) brother is a bit harder. The sound quality doesn't quite better the HUD-MX1's, even if you change the op-amps, but then it is cheaper and smaller. If you can afford the HUD-MX1 then it makes sense to ignore the HUD-Mini. If however the HUD-Mini just fits into your budget then it makes a great choice. You can always spend a few extra notes later down the line to play with op-amps if you're that way inclined.[/size]
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[size=medium] Here are some images comparing the Aundist HUD-MX1 to the HUD-Mini...[/size]
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[size=medium] As you can see the size has changed a bit. Apart from the Mini having less writing it only loses the power adaptor socket. The chassis of the HUD-Mini hasn't come down to the realms of the Fiio units, but they they do still have the larger USB, both sized headphone connections and RCA line-out's which make it great for desktop use.[/size]
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[size=medium] Here are a couple pictures of the internal circuitry to show the op-amps and tools...[/size]
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