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Audinst HUD-mx2 with Galaxy Note 3

A Review On: Audinst HUD-mx2

Audinst HUD-mx2

Rated # 69 in Amp/DACs
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Price paid: $248.00
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Pros: The sound was quite solid and with good resolution.

Cons: It is a pity that I should have a restraint in the place of use.

Meet HUD-mx2

As years go by, the smart phone became a vital part of our everyday lives and it is not much to say that the smart phone is a part of our lives. Although the smart phone causes many problems such as addiction to the smart phone, lack of conversation, etc., we cannot deny that it is an indispensable device. My life style is also changing little by little due to the smart phone. For example, about PC at home, I had turned on the PC every day before smart phones came into use. Now, however, I turn on the PC fewer times and solve almost all of the matters on the smart phone.


I can read internet articles, watch dramas, movies and play games without turning on the PC. I enjoyed upgrading PC peripheral devices such as mouse, keyboard, PC speaker and sound card. But now, I naturally turn my eyes to smart phone peripheral devices.


While I was watching dramas and movies on this smart phone, the thing that I have not been satisfied with was the sound. I recognized that the sound from smart phones reduced sensation of immersion. Of course, the simplest way is to put on the earphone. But I feel that it is also not satisfying. So I have looked for some audio devices to connect with smart phones, and most of the search results were portable speakers.


In particular, blue tooth speakers attracted my attention, but they cannot but reduce sensation of immersion, comparing with earphones or headphones. Of course, I could be satisfied with speakers. But as the one who enjoys listening through a headphone, I wanted to look for a device to connect with a headphone.


While I was making the search, I found DAC, which is compatible with Galaxy Note 3, i.e., a smart phone sound card, HUD-mx2 of Audinst. 





It is with a small size of 100mm X 120mm X 29mm, which can be held by a hand. The body is made of aluminum case and the finish is relatively good.

I feel that the exterior is in modern design, which is faithful to the basics. 








Headphone output supports 6.3mm and 3.5mm, and they both have the same impedance. Perhaps they made two sizes to prevent the sound from being decreased in case a conversion gender is used. They both support 600 ohm. When gain jumper setting is not made, they basically support 300 ohm. If you have a high impedance headphone of 600 ohm, you can open the case and change the jumper. Anyone can easily change the jumper, reading the user manual. As my headphone is 3.5mm, it seems that I would mostly use the right one.


Output Selection Switch

As you may know when you see the selector, you can select one between headphone and line output.

Line output is located in the back.


Input selection Switch

You can select one between optic input and USB input. They are also located in the back. And also you can select OFF in the middle. If you select OFF, sound output stops and it is converted to power saving mode. In the previous model, HUD-mx1, there is no OFF function. So this OFF function is a new one added to the subsequent model, HUD-mx2. You may think that the OFF selector is not an important one, but it is very useful to make you feel much more convenient. Just next to it, indicator is located. It is an operation lamp that shows current status by each color. 








There are optic input and output ports, and next to them, USB port where PC/notebook/smart devices can be connected. The smart phone can be connected to this USB port through OTG cable.

All devices generate heat when used for a long time, but the heat is not a level to be concerned about. I actually operated it continuously for 2 hours, and the device was warm rather than hot.

There were holes in the both sides and in the center of the back. It seems they cared about heat generation. 





Inside Composition

Relatively strong internal composition

I decided to undress the device. To undress the device, I need to take out the volume knob by using a contained hex wrench. I did not recognize the use of this hex wrench when I first saw the components. First remove the volume knob on the front side, and then, loosen the 5 screws on the back to see inside.  





Push in the volume control knob, and then, PCB pops out to the back side. 




VT1728A of VIA is used for the main chipset. By using EnvyUSB 2.0 Audio Controller, it supports USB input 24bit/96khz and samplerate of 44.1/48/88.2/96/176.4/192kHz. This VIA chipset may use exclusive driver, and can use Qsound and AC3 pass through function, and supports 24bit/88.2kHz, etc. This driver must be useful for the users who do not use it for pure DAC. Driver CD is not contained in the standard package. But an exclusive driver and user manual are in the official homepage of Audinst. 






It realizes dynamic range of 123db and deals with 24bit/192kHz by mounting PCM1796 of Brown company. As the IC is widely used and it is not much to say that the IC is generalized, the IC is quite stable. 


TPA6120A2 of Ti is inserted into headphone part for headphone amplifier chip. The chip is known to be excellent in driving force and ability.


In low-pass filter part, film condenser of WIMA, exclusive regulator, low-ESR and tantalum condenser are adopted for stable power supply. In DAC power part, low-ESR and high performance solid condenser are adopted. And also, high purity TCXO, which minimizes signal instability due to temperature and voltage change, is adopted.


It realizes the best balance, being mounted with LME49860 of National Semiconductor, the fixed SMD type OPAMP, and OPAMP OPA2227 and OPA2134 of Ti, the replaceable DIP type OPAMP, as basic. LME49860, which is in charge of the right and left side, is a SMD type part, so it cannot be replaced easily. But OPA2227 and OPA2134 of DIP type, which are in charge of final output, can be replaced by anyone. So you can easily tune the tone as you like. AS the OPAMP in the final output stage is designed to be easily replaced, you can feel the tone change by easily tuning the tone. Recently, most of the middle class DAC or sound cards are designed with replaceable OPAMP. 








Connection with Galaxy Note 3

To connect with Galaxy Note 3, OTG cable is a must-have item. The way of connection is shown well in the figure in the user manual. Seeing the way of the connection to the smart phones in the user manual, I feel that that they want to stress the relevance between HUD-mx2 and smart devices.

The important thing here is that you must connect an adapter. You may use it through USB, without an adapter, on PCs or notebooks. But when the device is connected to smart phones, it seems that the device works only when power is supplied separately. 












Headphone: ATH-A700 (Impedance 38ohm)

Smartphone: Samsung Galaxy note3


I feel certain that the sound becomes solid and clear when I listen to through HUD-mx2. I feel that the sound is crushed down when I listen to only through smart phones, not through DAC. But I feel clear difference in the sound with DAC.

In particular, I feel that the high-pitched sound is clear and well-arranged without bouncing. High-pitched sound may easily become sharp, but the sound through the device is felt well-arranged. When I listened to jazz and violin music, I could recognize the fact better. While I was watching the movie, I might say that the dialogues hit the ears better as the voice was clearer.

While I was playing the games, effect sound, i.e. feeling of hitting, was not bad.


The sound may be felt differently depending on headphone/speaker, sound source and the propensity of people. But in my humble opinion, people may get the above feeling in common with HUD-mx2.


In conclusion, I am satisfied with DAC in the aspect of doubling the sensation of immersion as I intended in purchasing it. But an adapter must be connected to use it with the smart phone. So I felt inconvenient as I should be around the socket to get supplied with the power. I wish it would be a portable product that can be connected to smart phones without an adapter. Of course, I could understand the point as the device is mainly for the use with PC/notebook, and the use with smart devices is a subsidiary application.

I want to compare it with other OPAMP later, if any. But as I am somewhat satisfied now, I will try later.




HUD-mx2 DAC is mainly for the use with PCs or notebooks. But I use the smart phone most of the time, and so, it seems that I will use the device mainly for the smart phone. I listened to the sound through the device on PC, and I felt similarly as in the case of the smart phone.



In my humble opinion, the sound was quite solid and with good resolution.


As I said above, the sound is evaluated very differently and subjectively depending on the output device and propensity of people. So other people may feel differently from what I felt.



It was an inconvenient point that an adapter should be always connected to use it with the smart phone. In order to use it, I should be always next to the socket. There is no trouble during using it, but it is a pity that I should have a restraint in the place of use.


Considering the use with smart devices, I hope that a portable DAC is made in the next time.


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