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Portable Amps item created by jacksonchansf, Aug 27, 2012
Pros - Warm and slightly bassy sound with decent detail
Cons - Boomy in the bass departement and while detailed, lacks depth.
Here we have MIU Audio’s or Miu Tech’s semi new MRB headphone amplifier. It is in the $100+ USD price range. IT is an intermediate level DIY kit where you put all the parts together. Surface mounts are already done. The op amps just pop in.
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The DIY of the MRB was pretty easy if you know how to solder. As with any build, you would need to get all your parts straight, measure them to make sure they are the correct values and meticulously put them into their locations on the board. IT was quite straight forward. The board was a bit small and there were many components. As a result, I’d call the build of intermediate difficulty. There were some problems however, with the DIY of the build. The biggest part was that the paper that came with the MRB telling you where each part goes was actually incorrect in one part. This caused three of us reviewers to each get a very big channel imbalance after it was complete. Head-Fi’ers Tilpo, b1o2r3i4s, and Deadly Lover were able to rectify the problem after receiving schematics from MIU. The problem was that the instruction sheet that indicates what components go where had a misprint. A resistor was switched. The correction has since been made. But this however does raise questions on quality controls at MRB. Another problem with the DIY build itself is that since it has a premade chassis and holes drilled, this ultimately leads to some holes not matching. This was not a big problem as some small soldering of the main parts like the volume part got it so that all three of us reviewers were able to get the main portions sticking out near perfectly. A bit cumbersome to some, but overall not exactly the hardest thing to do. However the back power recharge port does not match up properly. I have confirmed that all three of us reviewers had the power recharge port being slightly higher than the hole. Plugging the cable in however is not a problem and the port will lower down. Both a pro and con of DIY’s pre made chasis is that while you do get one that is nice and premade and nice looking, it may not fit some holes. But then we get the problem that all three of us reviewers had the power recharge port slightly raised nearly the same amount which again brings up quality control and if the manufacturer built even one unit after finalizing it.
WARNING: One of the last pictures in the set shows me with a pic of a regular non rechargeable Energizer battery, and the recharge cable adapter and an A/C adapter I had.YOU CAN NOT DO THIS. I was only putting them in the picture for pictures sakes. You NEED a rechargeable battery to use with the A/C adapter.
The build quality of the MRB is in my opinion pretty good. It is a pre machined metal chassis. It is very smooth and looks very nice. There are some rough spots and uneven screw parts that don’t 100% match and swallow into the chassis but that in itself is what I believe to be the grit feeling you get with a DIY build like this. Where the round screws slightly overtaking the rectangular box shell beneath it gives you a feel of DIY and your hard earned build. However even though it is made out of solid aluminum, it is not what I would call drop resistant. The case itself vibrates a bit when “hit” or anything due to the design. IT’s slightly heavy case and other factors due cause some concerns with dropping it as well so just don’t drop it.
The PCB inside is made pretty well. The battery side has a thin stretch or sliver of PCB that is about 3mm thick which is used as a “rail” to be slid into the chassis. That did give me some trouble when building it due to how thin it was and also is another factor in what would probably snap first given a drop, but the small thin stretch is in many other DIY builds so its not specific to this device in any case.
It is quite heavy for a “portable” amp and is also a bit bigger than something I would take around with me. The thickness is about 3X the iPhone 4S itself, add in an iPhone case to prevent scratching and what not and bam, we have a setup 1 inch thick. While thickness is quite common for many other amps, at this price range and with it’s sonic qualities. It is something that has to be taken into account
Nothing too special, a power switch, input, output and a volume pot.
Testing Method and equipment:
My reference setup will be:
ComputeràS/PDIFàAudio-gd NFB 12.1 Dual Wolfson WM8741 Fixed DAC outàCustom O2 with Burr Brown OPA2228.
Mainly tested with:
iPod Touch 2GàFiiO L9 LOD/HP out à MRB
iPhone 4S à FiiO L9 LOD/HP outà MRB
And also as well as testing with direct headphone out on both i-devices as well.
Sound Quality Section:
Highs: It’s highs are more pronounced and reach higher than would the i-Devices can. Although they are higher and thus open new doors for listening, they aren’t perfected up their. While not harsh, they aren’t smoother either, a bit of an elongated sparkle here and there with lingering and uneven highs that the i-Devices can’t reach. Whether the MRB is an improvement or not depends on if you want smooth, but not as present highs on the i-Device or the more pronounced and technically better high frequency response of the MRB.
Mids: The mids are a bit pulled back or distant on the MRB. This includes both vocals and guitars. They are in fact duller actually than say the iPhone or my “reference” setup. They are pulled back along with it’s bigger soundstage. IT really depends on what you like, but I don’t like the MRB’s presentation of the mids. While I can take a pulling back of the vocals, the dulling of the vocals so that it has a large dull mass in the middle type of feel and duller guitars is not something I like. Instruments at this range get more oomph to it, but they get too much that they just don’t go well. String instruments are too bloated and the mids are also a bit conjested with the lower and upper mids collapsing towards the middle so the mids are a bit more contained and dull.
Lows: There is much more mid bass with the MRB than with an i-Device. I wouldn’t say it is getting muddy or bland, but they do fill in some holes that the i-Devices have left with bass lovers. However a problem is that while the MRB does have some power, it will overvolt easily with most headphones in the $200 range. This means that the signal plateaus or clips, giving you a very very distorted sound in all areas. While this device does give you more mid bass to use, other devices that have a artificial bass boost EQ may be better if you want it. The upper bass is about the same on both i-Device and MRB. The sub bass however extends less deep than the i-Device but the upper sub bass has a bit more punch than an i-Device.
The soundstage on the MRB is wider than something on my 4S or Touch2G. It is wider and pulls the vocals and mids back a bit more. It is a nice thing to have for classical recordings or what others that have a need for wide soundstages. But as the mids are duller compared to an 4S’s headphone out, it can’t exactly be said to be better for strings either way.
At $112 not including tax, customs, shipping if any of these are applicable and also the need for self DIY’ing the thing together, this can be seen more as a hobby rather than a ‘good deal’. Where the entire process of getting it, following directions and building it to using it brings joy and other things to the user. All the parts have been bought by MIU and you just go and build it, which is something many headphone users don’t do as they don’t want to or know how to get DIY audio parts and components. The sonic qualities of the MRB in my opinion are decent. They do have many qualities that are usually looked for such as a better bass response, soundstage, pulled back mids and better highs. But they are just not executed well, the sonic qualities that is. It has qualities that people have said that they want but it just doesn’t and isn’t able to do it as well as a headphone enthusiast would care for. The initial problem with a wrong build paper set back this review by more than a month and also was not very positive in my experience with the MRB. But overall the experience of building it with a pre made nice chassis was quite an experience that you don’t see many offer. I would more say that the MRb should be a hobby kit for those that want a kit that is just hard enough with no prior instructions on how to solder and equipment needed but are also adventurous enough to want to go and tackle it themselves and ultimately be rewarded with an amplifier.
These scores are based on price.
I wish to thank HEad-Fier Tilpo and Swimsonny for helping me cross reference my build with theirs. Tilpo also aided me in proof reading and revising this review that you see before you. HEad-Fi'ers b1or2i3s4 and DeadlyLover also get a heads up for their aid in looking at the MIU MRB Schematics and rectifying the problem. The idea for the small consecutive images across the sections that pertain to the pictures was used or first seen by me from Head-Fi'er Warrenpchi, he didn't want credit for this "idea" but he shall receive it none the less.
My peers Tilpo and Swimsonny also received review samples and their reviews are here:
Thank you to MIU Audio for arranging this review sample.