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Three Stones MiniBox-E+ - Review of a Humble Sleeper (LOTS of PICs)

post #1 of 384
Thread Starter 

My interest into this amp was piqued by mrarroyo impressions as posted here: http://www.head-fi.org/forums/f105/c...ot%3BMiniBox-E

I was reading in disbelief that mrarroyo would declare his preference to MiniBox-E+ over the RSA SR-71, SR7-1A and Xin Reference. It’s impossible I thought. Those amps that he pitted the MiniBox-E+ against are all heavyweight top contenders, treasured by many for their sonic capabilities.

But I have always trusted mrarroyo judgment more than anybody else, partially because perhaps we share similar listening curve. It was mrarroyo and Vorlon1 who prompted me into Xin amps fandom and I have been a zealous supporter since then.

Over a month ago when I was in the market seeking a companion amp for my SuperMini-IV (2008), I have my eyes fixed on several choices, budget was not a big concern because I have decided to spare around $500-600 for amp alone. With the bludgeoning interest in RSA twins P-51 Mustang and SR-71A all over the place, it was a daunting task to fend of the temptations. Pico was in the list too. I did consider Lisa III but I have an issue of adding another long brick to my already fat rig setup (the DAC alone is as big as Lisa III). TTVJ Portable Millet was in the list as well but I was put off by the pinging issue that some users have complained about.

I have some strict requirement for the next amp purchase, it must be able to synergize with my aged ER-4S and preferably with bass boost option. My SuperMini-IV has spoiled me for wanting these features because listening to ER-4S without the bass boost is no longer acceptable. This doesn’t mean that I am a basshead now. But the SuperMini-IV has introduced an organic balanced tonality to the ER-4S and made it a lot more musical and engaging. Knowing that Ray didn’t use ER-4 in building his amp, I decided to skip RSA camp altogether and started looking elsewhere.

Then came the review from mrarroyo and I thought I have found the right candidate. Even if only half of the impressions made by mrarroyo is accurate, it is still a real bargain to be had for – Xin Reference is a novelty amp that have perhaps like one year wait queue and the RSA SR-71 is simply out of stock and no longer manufactured. Compared to the Xin SuperMini-IV, they shared practically 100% similar functions – Bass Boost, PtoS (75 Ohm), CrossFeed (SFOR), Roll able Opamps, Buffers etc. But spending $239 on a relatively un-glamour amp is somewhat a daunting move, yet I find myself emailing Nankai (Fang) of Head-Direct asking for shipping quotes. And so it was concluded, my MiniBox-E+ is on the way (this was in December 2008)

Buying and dealing with Head-Direct
The amp ships from USA. I opted for the USPS International Priority Mail which took 10 days to arrive. I would have asked for expedited express mail but Nankai advised me that the charges will be near to $100 which is absurd if you ask me. Nankai should have subscribed to Fedex or UPS where they will charge around $55-75 for expedited 3 days shipping (I paid $75 to Ray Samuels for my Tomahawk). Since I still have my SuperMini-IV to accompany me, I can deal with the wait.

Nonetheless, I am happy with the communications with Nankai. He responds to emails and PMs whenever he is online. Much similar to Ray Samuels legendary practice

Throughout this review, I will be making heavy comparison and reference to Xin SuperMini-IV 2008 and Xin SuperMicro-IV (04/11 Edition) which I am very fond of and familiar with.

The Amp as Advertised

Three Stones MiniBox-E+
OP-AMP requirement: Most DIP8 mono op-amp
Frequency: 10Hz-60KHz??v-3dB/+0.7dB??
Output Impedance:16Ω-300Ω
SNR: >110dB
THD+N: 0.0035%
Battery Type: Li-ion
Battery charge time:10~15 hours
Battery Work Life:about 60 hours
Dimensions: 80mm*67mm*16mm

The Amp that I Received

Nice chocolate box?

As can be seen here, there’s significant difference in the amp that I received. Notably the SFOR function is no longer included. The lever switch has been swapped for a push button model. The version that mrarroyo have was identical to the advertised pictures, so I assume that this MiniBox-E+ is a third revision from the original unit, mrarroyo’s being the 2nd revision.

Build/Form Factor
MiniBox-E+ is notably different from most amps from the look itself. The rather slim profile is quite nice and it is made of metal (aluminum I assume). But It is also wider than most amps. To me, the form factor is quite attractive because it will consume less rig stacking space compared to the popular Hammond enclosures used by Xin, Practical Devices, Portaphile V2, AMB Mini3, GoVibe V6 etc.

At first I didn’t quite like the white face front and rear covers, they are made of the same material that’s used for the amp board. I would have preferred them to be made of aluminum as well. But they turned out to be quite solid and very well cut. The unit itself is very easy to disassemble provided that you have the right hex key. I used my jeweler flathead to work the hex bolts. The casing itself is a two part enclosure that can be slid open and thus making it easy to roll Opamps.

Overall, the build is quite solid. Of course it is not as tank-like feeling as can be found in Ray Samuels’ amps.

The push buttons turned out to be quite handy because they do not protrude much to obstruct rigging of cables if you plan to use right angled plugs. To disable the bass boost, the button must be in “on” position. Same goes for the PtoS (75 Ohm) function, pressing it in will disable the higher impedance switch.

Much similar to Xin SuperMini-IV, old styled volume wheel is used in place of the more popular volume knob. While I don’t quite like the recessed SuperMini-IV wheel, the MiniBox-E+ is actually easily accessible due to the wheel being placed with generous exposure. The thicker width does help as well. And on top of that, the wheel rotates effortlessly without being loose. The Xin SuperMini-IV is notably tougher to rotate and does not have any marker to indicate volume levels

Included together with the unit is a pair of custom interconnect and an 18V power adapter. I practically didn’t use the IC at all because I already have a few silver ICs ready.

The Driving Power
One of the primary factors for me to choose this amp was because it is powered by an 18V battery. From what I have learned, the majority of the better sounding amps out there are those belonging to the 18V group like the Lisa III, RSA SR-71, Larocco PRIIMKII and a few others. Even Dr. Xin who is well known for conjuring miracle out of small voltage powered amps is shifting to higher power supply with the upcoming 12V Xin Reference (Type D and above).

I am a strong believer in better sound through higher electric current. That deep and commanding bass can only be made possible through steady and meaty supply of electric. Similarly, substantial power supply will help to establish lush highs that will not singe the eardrums. More on this later.

As can be seen in the pics below, the battery is actually composed of two flat cells as commonly found in DAPs. The only difference is that they emit no less than 15V of juice. I take it the MiniBox-E+ have a boost (similar to Xin) to make up for 18V total. This is a revelation because all of the 18V devices out there use two 9Vs. The slim 18Vs make it possible to attain a highly slim profile.

Head-Direct claimed that the MiniBox-E+ will take 10-15 hours to charge. But for some reason the charging indicator on my unit will switch off within an hour or two. With the bass boost turned on, my amp can only last no more than 10 hours with or without load. I have to confess that I am a bit troubled with this. It may seem that my unit may have a flaw in the charging circuit but I choose not to be bothered with it much for now.

And yes, an 18V Adapter is included with the amp. Can be used both for 110V and 220V.

The Amp Design/Internals

One of the main appeals for this amp is the dual mono amplification for left and right stereo. As can be seen in the pics, the dual mono path is clearly visible – simple and intriguing.

The BUF(634) chips are permanently attached to the board unlike the SuperMini-IV where you can swap them out. I am not too concerned about this as I don’t have plans to roll the buffers.

Almost similar to the Xin SuperMini-IV, OP8610A is used as the stock opamp. The SuperMini-IV comes with two AD8610 and I am not sure if the OP8610A is a sibling of some sort to the AD8610. But both are single opamp meant to be used in pairs.

Like the opamps, the MiniBox-E+ uses two caps which is not a common practice nowadays. The SuperMini-IV have one 1000uF capacitor and the MiniBox-E+ uses two 1500uF caps making the total of 3000uF capacitance

Burn-In Curve:
As a normal practice, I believe every solid state amp will benefit from burn in. No exception here. The two caps will need some hours through them to form. Coming from Xin camp, I would normally expect no less than 800 hours to stabilize into their intended state. My MiniBox-E+ just barely clocked 350 hours from the day I received it. Unlike Xin amps, the burn in curve is not as erratic. There’s no wild swing that I have observed with the SuperMini-IV and SuperMicro-IV present. But at certain intervals, I do hear some changes like the bass losing weight temporarily and highs getting a bit spiky – but they are very subtle.

Reviewer Preference:
I am a long time ETYMOTIC ER-4 user and self styled zealot. My rigs have changed faster than woman handbags at times but my ER-4 is always there to stay. This review has been conducted 100% using ER-4S as the only and primary listening device. My goal is to find a match for my ER-4S that offers a lot of synergy and by saying this I am specifically into smooth sounding source to complement my finicky ER-4S. I have always believed that ER-4S will benefit tremendously from proper amplification and I have been proven right with various tests that I have gone through over the years. Plugging my ER-4S to a home CD rig shown me what ER-4S is capable of. Hence I am on the quest hunting for the right amp and source and now I have this wonderful little amp to play with

Listening Trials

Companion Gears:
-ETYMOTIC ER-4S IEM (ultramodded & recabled) + Stock ER-4 Foamies
-iRiver iHP-120 Rockboxed (Optical & Line-Out)
-Panasonic SL-CT700 PCDP (Optical & Line-Out)
-FLAC Q3 CD Rips & CDs
-Bengal LLC Optical & DIY Toslink-Mini Cable
-12V HifiDIY.NET PCM1793 OS DAC with OPA2134PA Preamp
-Pure 5N Solid Core Silver Mini-Mini Interconnect with Switchcraft plugs

* The ultramodded ER-4S is equipped with permanent 96 Ohm inline TKD precision resistors and recabled with solid core 5N Pure Silver. They are sonically smoother sounding than the stock ER-4S but notoriously hard to drive.

A variety of artists including Diana Krall, Nick Cave, Morrissey, Pelican, ISIS, Joy Division, Ultrasone Binaural Sampler, Suzanne Vega, The Cure & some classical stuffs

Pretty much the genre span from Jazz to Metal to Classical and Indie/Pop

Listening Approach:
For the past three weeks, I have been listening to the amp in every conceivable combo that I can think of with my existing rig. Primarily I will be pairing the amp with my iRiver+DAC combo but while at home, PCDP+Lineout were used as well. The majority of my impressions will be based on DAP+Lineout configuration because that is the most commonly used setup in a portable rig.

Sound Review

There’s not much can be expected of an IEM when it comes to soundstage. Closed armature drivers are cursed not to have the airy openness like open backed dynamic drivers no matter how it is configured. The best one can expect is NOT to have as if the sound is RIGHT in the middle inside the head. Much similar to the SuperMicro-IV, the MiniBox-E+ offers generous width and spaciousness in soundstage. This is what I find missing with the SuperMini-IV which fall short subtly in contrast. There’s a touch of dynamic airiness to the sound that I am very fond of when I first experience it through the SuperMicro-IV. The left and right orientation still dominates the staging but the placement is definitely distinctive. It is possible to imagine the placement of instruments and passage direction – the separation is crystal clear and it is easy to focus on a specific sound if the listener wishes to. This clear and spacious staging helps to instill non euphonic sound and avoid congestion. Playing Ultrasone Binaural sampler tracks confirm this. One of the sampler tracks contains a myriad of instruments up to 5 layers of passages and the MiniBox-E+ have no problem handling and separating them, almost effortless.

With the bass boost switched on, the mids gets warmer – noticeably warmer if compared to with bass boost switched off. Nick Cave and Diana Krall vocals sounded deep and rich – very lush. At the same time, it is still very realistic and transparent. Despite the warming, they don’t sound out of place at all. They are quite consistent as one would expect hearing them live – a touch of organic boomy-ness where it should be and whispers when there is one. Any other instruments that inhabit the mids are treated similarly, there’s noticeable lushness to violin, guitars, piano, saxophone etc - they don’t exhibit any uncanny hump and the edges are silky smooth, sometimes ended with natural sounding decays. At first I am unaccustomed to this and find it hard to attune to the new sound, but now I have grown addicted and find myself spinning the same songs over and over again. In contrast, the SuperMicro-IV sounds a bit more neutral because it does not have the bass frequencies boosted like the MiniBox-E+. SuperMini-IV on the other hand has slightly lighter warmth with the bass boost option enabled.

This is where the MiniBox-E+ shine best. Since I am almost permanently on bass boost and getting addicted to it, I could no longer bear to have that function turned off. There’s a rediscovery of balance to the entire spectrum with the bass boost. Long regarded as a cold sounding IEM, the ER-4S is a lush pounder now. Bass is still very tightly controlled but now it has commanding authority in visceral impact and slam. Presence is also improved drastically – where there’s bass, one can clearly feel the vibe kicking in with excellent reverb around the ear canals. It’s groovy actually. Listening to my Metal, Electronica and Indie collection through the ER-4S has never been this engaging. Be it percussion bass, stringed bass or Diana Krall’s cello outfit or electronic induced vibes, the MiniBox-E+ rocks them solid – and with authority. The best part is that, if there’s no bass note present (or very minimal), the sound will remain faithful by not “projecting” any artificial bass hum or anything like that – very realistic.

This is the most interesting part. Treble no longer jumps with “in your face” emphasis. In fact I can audibly hear that treble has been spaced out a step back. No overbearing presence that I can tell of. There’s some serious silky smoothness to the presentation now. The edges are lush with swishy decays, not too long, not too short either. We are talking about very high quality treble here. The extension is properly textured giving the impression of cleanly layered and staged treble body. Gone are the annoying glare and hardness. Simply put, I feel no fatigue even after long hours of listening. Some may even call this different presentation as recessed. In a way it is true, but if one chooses to focus on the treble, they are still there in full flavor – just that it is no longer glorified as how an ER-4S would project while plugged in to most other amps. In contrast, the SuperMini-IV and SuperMicro-IV will still retain the upfront projection which can be a bit too much on some funky recordings.

Being warm sounding does not mean an amp must be less transparent. To me transparency is about projection of sound with the least amount of obscurity. Without a doubt the MiniBox-E+ is a transparent amp. I wish I have some better words to describe this, but I think listening to the amp itself will tell the story better. Ok, simply put, the sound coming out of this amp is so clear that it is easy to forget what is there between the listener and the music.

As per expected, there’s lots of details all over. A typical ER-4 junkie will not be disappointed the preservation of details in each note. If there’s something there in the sound no matter how small, one could still pick up the miniscule details because the rest of the sound spectrum does not intercede or mask the presentation. All three amps – MiniBox-E+, SuperMicro-IV and SuperMini-IV shared common prowess here. I could not decide which is more detailed than the other.

Always a fast performer, ER-4S is expectedly fast. The MiniBox-E+ pace up commendably to match ER-4S speed. No matter how complex the passages are, they will not get flabby or sluggish. This is quite apparent in some classical tracks that boast multiple instruments intertwining. There’s rich distinctiveness to the timbre because the overall warmth has improved the sound definition – very organic and realistic definition that is. It is easy to discern between a trumpet and a saxophone, or a cello pluck from bass guitar strings. This sort of speed is dead identical to the SuperMicro-IV and the SuperMini-IV just a hair behind.

Percussions are another passion of mine. I am immensely addicted to barrages of drum attacks and find myself listening a lot to ISIS, Pelican, and Joy Division for their infectious drums. MiniBox-E+ has improved the reverb, echoes of drum thuds and decays. I like them loud but at the same time I don’t want them to be overpowering and MiniBox-E+ delivers. In this dept both MiniBox-E+ and the Xin duo are on par – drum junkies will be very pleased with any of them.

Sibilance Handling
On a very positive note, the MiniBox-E+ has done a tremendous job in reducing vocal sibilance commonly heard through a bright sounding cans like the ER-4 (most notably the ER-4S/B). I have had lots of problem listening to Joy Division’s Ian Curtis and TEXAS because their voice are so high pitched and will always surely ended in that dreadful long “SSSS”. But now it’s very tolerable. The sibilance has been controlled significantly – partially perhaps due to the overall warming of the entire sound spectrum. Definitely a must have feature for all bright sounding cans. This is where the Xin duo loses a bit of ground as both are not an excellent controller of sibilance; they are good but after listening to the MiniBox-E+, the differences are quite apparent. I guess this is a price to pay for being very detailed and sensitive.

Background Window
Just like the Xin Duo, the MiniBox-E+ is dead silent when there’s no music on play. Because it is a very detailed and sensitive amp, the only noises that I can pick are those coming from the records itself.

Source Matching
I am a strong believer in good source. The rule “garbage in, garbage out” applies. The MiniBox-E+ will simply amplify what is being fed to it. When rigged with my transportable iRiver iHP-120+Optical+PCM1793 OS DAC (OPA2134PA Preamp) and fed with lossless only, the amp sounds blissful and very analogue. But when I plugged it to my Laptop headphone out, it is a bit digital sounding – still good but a bit plasticky. In contrast, the Xin amps will retain their distinctive signature and variance is not much no matter if you plug it to an iPod or an iRiver line out.

To me, the MiniBox-E+ does not sound like a portable amp at all. It has commanding authority almost everywhere. The sound is very organic and very analogue. That 18V driving power is a huge factor for it being very good sounding. Like I mentioned earlier, most great amps will boast impressive driving power when fed with at least 12V and above. There’s substantial current supply to emit deep and impactful bass, enough power to prevent treble spikes.

Most importantly, I find the MiniBox-E+ to be a modest and realistic amplifier – there’s no hint of exaggeration or hardness – something that most other amp fail to accomplish, that simplicity of being powerful yet humble. The SuperMicro-IV is a very energetic amp and this can spell disaster with funky and loud music – listening to Lo-Fi Metal, Indie or Punk music can be painful because they amplify all the annoying noises as well. So in this regard, one can say that the MiniBox-E+ is a better all rounder compared to the Xin duo.

It is beyond any doubt that the MiniBox-E+ is a keeper. I will continue to buy Xin amps and perhaps a few others from the RSA camp but the MiniBox-E+ are here to stay.

Post 400 Hours Update:

Going well over 400 hours, I am continously amazed how this amp have evolved. It does not evolve as drastic as the Xin amps but my ever sensitive ER-4S did not fail to aknowledge the refinement. The airiniess level in the notes now clearly rival Xin SuperMicro-IV and the richness in Timbre distinction is becoming even more apparent. I am absolutely addicted to the effortlessness to the sound flow - yes it flows with great ease and smoothness.

But it have to be mentioned that I do not credit the amp alone for this blissful experience. Like I mentioned earlier, the source matters a lot. I realised that my PCM1793 OS DAC have also eclipsed the 250 hours mark and this means the bunch of capacitors on the DAC unit have settled in. It is good news indeed for me because there's some serious symbiotic synergy going on there. The OPA2134PA Preamp does a stellar job in matching with the pair of OP8610 opamps.

On the other hand, I am also continously amazed how receptive the ETYMOTIC ER-4 responded to amplification. They scale up nicely as the ante are upped. A quick listening test to my spare KSC-75 confirmed this, I still can't find any joy listening to the KSC-75 anymore because the gap of refinement offered by ER-4 is simply too huge.

And I have not even start rolling opamps yet. mrarroyo suggested AD797AN for tubey signature. I have them on order now. With rollable opamps option, the posibilities can be endless - but I don't intend to drag myself into that limbo and probably will roll only a few mono opamps.

For the last two years, I have always placed Xin SuperMicro-IV as the No.1 amp. With what I have now things have changed and I will openly declare that the crown has been passed ot the venerable MiniBox-E+


Opamp Rolling Results
During the Lisa III trials, I have the opportunity to sample a couple of opamps. The intention was to match as much as possible the vibrant sound of Lisa III. At first I attempted the AD797AN which was suggested by mrarroyo. But apparently the 3rd Gen of MiniBox-E+ which is the one I am using now does not seem to work properly with the AD797AN anymore, there was a nasty screeching sound when the volume wheel was scrolled. So off the AD797AN go.

I was lucky with my 2nd set. Through advice by a seasoned HiFi DIY Junkie, I acquired a pair of AD8065AR (mono opamps). Suffice to say that I was floored with the results. AD8065AR was much more vibrant than the stock AD8610 - period. Bass was highly textured and plentiful that I find it possible to turn off the Bass Boost switch. Most importantly, I don't lose the analytical details and separation of instruments was even more apparent than before. The highs remained the same with AD8610 which is exactly what I have wished for.

It would not be too extreme for me to claim that the combo of AD8065AR has helped my decision to sell off the Lisa III because at that state, the MiniBox-E+ was already performing in the same league with the highly celebrated Lisa III
post #2 of 384
very good review. I have one minibox e+ and it's very good compare to my 3move
post #3 of 384
A fine review. Can it play while charging?
post #4 of 384
Wonderful. Absolutely wonderful.
post #5 of 384
Very good review. A pleasure to read. So how do you rate new (2008) Supermini?
post #6 of 384
Hmm, might have to snap up one of these in China next week
post #7 of 384
Thread Starter 
Yep it can play while charging

I am not in the habit of ranking amps. All three are worderful and if I were to have only one of them at any given time, I will definitely be happy. The exception is, SuperMicro-IV synergize better with ER-4P and SuperMini-IV & MiniBox-E+ with ER-4S.

The SuperMini-IV 2008 is a very special amp. With bass boost switched on, ER-4S springs to life with zest and wholesome vibe that not even the venerable SuperMicro-IV can match. MiniBox-E+ offers the same except that it have more air to it.
post #8 of 384
EFN. Try finding a pair of CD3000's. You'd be in for a treat since you're an ER4S lover like me
post #9 of 384
Thread Starter 
Originally Posted by ZephyrSapphire View Post
EFN. Try finding a pair of CD3000's. You'd be in for a treat since you're an ER4S lover like me
You want to wreck my wallet izzit? LOL! thanks for the advise.
post #10 of 384
Originally Posted by EFN View Post
You want to wreck my wallet izzit? LOL! thanks for the advise.
No lah. I miss speaking Manglish.
post #11 of 384
amazing review. really something to consider.
post #12 of 384
I called TTVJ last week to inquire if they have the minibox-E+ in stock. They're out and they do not know when they will receive any.
post #13 of 384
Indeed a very interesting read. Do you have any idea how this amp would work with higher impedance full-size cans? I need an amp for my beyer DT150's and I'm looking at either this, the ibasso D3/P3, or a little dot MK I/+. Seeing as you make comparisons to the RSA/Xin amp range, the minibox seems like a great offer.

post #14 of 384
Thread Starter 
You can read the original impression thread by mrarroyo and even PM him. he uses full sized cans and I only use IEM. My ER-4S is anything but efficient due to the upgraded inline resistors - even harder to drive than stock ER-4S which is rated at 100Ohm. There's a lot of juice coming out of my PCM1793 DAC preamp that I have to turn the volume wheel down within the range of 2-4 and not more. While plugged on to my PCDP or iRiver Lineout, the volume wheel need to be adjusted to 3-6.

Latest Update:
Based on my calculation, my MiniBox-E+ has just clocked 400hours! woohoo!. There is noticable difference. There's more airiness to the notes now, strikingly similar to Xin SuperMicro-IV. I am talking about that Alessandro MS-1/MS2i kind of airiness which I am addicted to. Gosh it's getting better this thing lol
post #15 of 384
Thanks for the review, EFN.

I assume this amp does not hiss with ultra-sensitive low impedance IEMs when the PtoS resistance is turned on... how does it perform hiss-wise without PtoS?

Anyone with a SE530, UE10/11, S.F5 tried the Minibox? I'd be interested how "black" it is (since I'm severely disappointed at the iBasso T4 in that aspect).
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