Multi-Portable Amp Thread: 12 amps reviewed (Shonyun 306 added 10/03/12)

Multi-Portable Amp Thread

Amps mean different things to different people.  It depends on your use, music,  source, headphone, and ears to determine if an amp will make a difference, and if so how much.  As primarily an IEM guy, I have had mixed results with amps through the years depending on the factors I mentioned, and while this review thread can’t possibly cover all the iterations of product combinations, it will compare the general performance of each amp.  I do have more specific amp matching with headphones/sources in my custom IEM reviews.  My Google+ page.

click images for full sized picture

Portable amps reviewed:

-          Headphonia Arrow 12 HE

-          Headamp Pico Slim

-          Meier Audio Stepdance (original)

-          Neco Soundlab DUAL AMP portable headphone amplifier – V2

-          iQube V2 (with DAC)

-          Auzentech i.Fuzen HP-1

-          Furutech Cruise (with DAC)

-          Just Audio uHA-120

-          Portaphile 627

-          Epiphany Acoustics EPH-O2

-          Headphonia Arrow 12HE 4G

-          Shonyun 306

But, before reading further, here are my notes from testing:

- I primarily review and listen to custom IEMs and some, such as the JH16, LS8, and Infinity X3 are not dependent on the quality of the amp and there are small to minimal differences between the amps to my ears.

- These amps are fairly close in sound signatures and the differences between the amps is not as large as the difference between headphones/IEMs.

- The differences between the amps in frequency response is very minimal.

- A good amp can improve the sound of lower end headphones, but a good headphone from the headphone out of a relatively low end source (Clip+ or iPhone) can sound better.  Which is better overall depends on the combo and what you want.  I have heard what I consider huge improvements from some combinations such as the Ortofon e-Q7 and the ALO Rx amp or a MEElectronics CC51 and the Meier Audio Stepdance.

- With lower end DACs the differences between amp performance is less than with higher end DACs such as the Anedio D1 and HiFiMan 801, as would be expect.

- Using an amp from the headphone out of a player has marginal improvements for either output impedance mismatch reasons, or internal PMP amp limitations.  For example an iPod/iPhone/Fuze sound better to me from a line out than when amping the headphone out.

Important notes about the charts and ratings: The relative differences between the rating numbers are not all that large.  For example a score of an 8 in the bass isn't an overwhelming difference, but is very apparent in comparison with something rated at a 5.  While I didn't list synergy with various headphones, some react differently with certain headphones, however the relative sound and technical ability is usually remains the about the same comparatively. 

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Manufacturer: Headfonia
Model: Arrow 12 HE
Price: $249
Product notes: discontinued, replaced by the 3G and soon to be replaced by the G4
Type: portable amp
Volume control: analog, wheel
Power connector: USB (mini B)
Features:
- gain switch (0, I, II)
- bass switch (0, I, II) - 0db, 6 dB, 12 dB
- crossfeed (0, I, II)
- impedance switch (0, I, II)  10 ohm, 70 ohm, 120 ohm
- auto power off mode (3 switch positions: on/off/auto - auto turns the amp off after 60 seconds of no input signal)
- two input locations   
- slim design
Works with 4 pin headphone plugs: Yes
Sound signature: A spacious and warm presentation that generally adds width to the presentation while not necessarily adding to the depth.  The low through mid-bass is slightly elevated but the sub-bass is not.  Due to the bass presentation and spaciousness, the midrange seems slightly more laid back and the treble is more neutral/laid back.
Sound quality: The quality of the Arrow 12 HE varies greatly depending on the IEM and headphone due to the high output impedance as with many custom IEMs that have crossovers the sound is on the flatter side while others such as the TS842 (and ER4P) improves quite a bit with the impedance switch turned on, adding smoothness to an edgy and analytical presentation.  Overall, the resolution is a step below others such as the Pico Slim and Stepdance, but not always.  Driving full sized cans, the Arrow 12 HE does an acceptable job but the slim portable design does show limitations in dynamics compared with something more powerful such as the iQube, Stepdance, or Neco.  When paired with dynamic driver IEMs the sound is overall good and other than deep bass roll off for lower impedance headphones/IEMs, there is no effect of the output impedance.
Channel Imbalance: Yes, at very low volumes only with high sensitivity IEMs
Hiss: There is no appreciable hiss with the JH16 on low gain at max volume or below.
Interference: Slight clicking with the iPhone 3G when the phone is connecting to the internet.  No interference with the Blackberry Bold.
Summary: The Arrow 12 HE was a great amp when it was released due to the combination of size, shape, performance, and features as well as the amazing driving ability due to the three gain settings.  Still OK by today's standards, there have been other amps that have surpassed the performance of the Arrow 12 HE including the prototype G4 that I had a chance to audition.  The Arrow 12 HE really is dependent on specific matches with balanced armature IEMs as the output resistor either helps, hurts, or doesn't affect the sound, but you won't know unless you either try or read about it from others.  Dynamic driver armatures do respond well however as do lower end headphones.

Preview: I had the opportunity to try a G4 prototype board and the improvement was anywhere from a decent amount to substantial depending on the headphones used.  The G4 has more resolution and is closer to the performance of the Pico Slim and Stepdance and I am looking forward to hearing the G4 when it is ready.

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Manufacturer: Headamp
Model: Pico Slim
Price: $399
Product notes: The Pico Slim is the smallest high performance amp I know of and the size and shape make it perfect for on the go use with a minimal size addition to your source for powering IEMs and easy to drive portable cans.
Type: portable amp
Volume control: digital, knob
Power connector: USB (Micro B)

Battery life:
Features:
- Tiny size

- On/off switch which allows you to leave the volume where you want it between listening sessions
Works with 4 pin headphone plugs: Yes

Sound signature: The Pico Slim has a very transparent and fairly neutral sound that is on the brighter side of the spectrum.  It does not lack deep bass oomph, but the deep bass isn’t quite as accentuated and powerful as other amps such as the Stepdance or Cruise resulting in a slightly thinner sound.  Overall the Pico Slim doesn’t add much coloration to the sound and offers very good transparency.  The soundstage is on the average side but does offer very good depth and proportion to the sound resulting in a realistic yet somewhat intimate sound.
Sound quality: With exceptional transparency and very high levels of resolution, the Pico Slim performs very well technically.  The biggest issue I had with the Pico Slim with BA IEMs is that the notes can become slightly thinner than usual, and with some already thinner sounding BA IEMs this is not my ideal sound.  However, overall the results are exceptional.  With dynamic driver IEMs the Pico Slim performs quite well, however it doesn't have the bass control of some of the larger amps such as the Stepdance, iQube, and Cruise.  The Pico Slim isn't great at driving harder to drive headphones except for fairly low volume listening, and then it is on par with the Arrow 12 HE; good but not great.
Channel Imbalance: No

Hiss: Turning the volume knob up past the halfway point with the JH16 results in audible hiss, however when music is playing that volume level is louder than I would listen.  The hiss could be an issue with a low volume source, but I have not come across one that has caused an issue.
Interference: No interference from both my Blackberry Bold and iPhone 3G
Summary: For the size and shape the Pico Slim is a great little amp.  It offers exceptional transparency and plays well with custom IEMs, including high sensitivity ones, as well as dynamic driver IEMs.  Both the Arrow and Pico Slim are very easy to carry around with my modded iPod and the Pico Slim gives me consistently great sound, although in direct comparison the thinner and brighter sound if the Pico Slim doesn't always match well with brighter and thinner sounding IEMs.  With absolutely no imbalance, no interference, and no hiss in my experience the Pico Slim is an excellent choice for high sensitivity custom IEMs. 

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Manufacturer: Meier Audio
Model: Stepdance
Price: $349
Product notes: Discontinued; replaced by the 2stepdance.  I have owned the Stepdance for a while and have noticed it is a great performer with a wide range of headphones and IEMs rarely having a poor match.
Type: portable amp
Volume control: digital, knob
Power connector: Non-standard, for power only; unit does not charge battery

Battery life: Up to 8 hours with 600 uHa rechargable in low gain, high current mode, but typically closer to 6
Features:
- Active ground that simulates balanced in a single ended design

- Low and high gain switches

- Low and high current switches
Works with 4 pin headphone plugs: Yes

Sound Signature: The sound is on the warm side, but not all that warm, however the deep bass region does have some extra kick to it to go with the superb control.  The midrange disappears and is neutral while the upper mids and treble are slightly on the brighter side of neutral.  The width of the space scales with better DACs a bit better than average amp I reviewed while the depth and imaging are average.

Sound Quality:  Bass control is the first thing that comes to mind when I think about the Stepdance, but it has so much more to offer.  I was actually surprised by where the amp rated overall in my scoring system as it really doesn't do anything wrong. Resolution is very good with a slight liquidity to the presentation and better than average smoothness leading to a fairly transparent sound.  The Stepdance can drive harder to drive cans quite well and to loud volumes, performing in the top half.

Channel Imbalance: No

Hiss: Hiss is dependent on the volume setting and turning up the volume will result in more hiss.  I hear no hiss at normal listening volumes with any headphone/IEM I tried.
Interference: None.
Summary: The Stepdance has impressive sonic performance for the size and price with the ability to drive just about anything.  The bass is one of the best I have heard in a portable amp with a combination of control, depth, and punch.  This is the only portable amp that requires an external battery charger, but it can accept other external batteries of up to 15V if you choose to carry one.  With an overall great performance the Stepdance would be a recommended amp, but now that the 2stepdance is out and uses different op amps I am not 100% sure how that amp performs.

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Manufacturer: Neco Soundlab
Model: DUAL AMP portable headphone amplifier – V2
Price: $161 ($117 + $23 for AD8610 opamp + $21 for 600 mAH li-ion battery)
Product notes: Neco, the amp designer, is a great guy and will be happy to work with you on your custom needs fot the amp.  Thank you Neco!  This is the lowest cost amp in this review, therefore it stands alone.  I have owned a few amps in the same price range, but none have preformed to the level of my Arrow, yet the V2 does. 
Type: portable amp
Volume control: analog, knob, logarithmic
Power connector: Custom connector

Battery life: 24 hours at low volumes
Features:
- On/off switch which allows you to leave the volume where you want it between listening sessions.

- Logarithmic volume control for less low volume channel imbalance
Works with 4 pin headphone plugs: Yes

Sound signature: The V2 is a fairly neutral across the spectrum with an ever so slight bump in the midrange.  If it weren't for the slight bump in the mids, the V2 would be flat. 
Sound quality: For the price the V2 performs quite well.  While it isn't the best performer, it holds its own and is slightly better than the amp section of the D10 and does best some others in certain categories.  It has very good dynamics while the soundstage and imaging are average.  The V2 performed about average pushing the LCD-2, which is impressive for the price.

Channel Imbalance: Yes, at low volumes with very high sensitivity custom IEMs such as the JH16.  I initially received the amp with a standard volume control and the imbalance was much greater.  Let Neco know what you want and he will make an amp specifically for you, including a lower gain if you want to use the amp with high sensitivity custom IEMs.

Hiss: Hiss is dependent on the volume setting and turning up the volume will result in more hiss.  I hear no hiss at normal listening volumes with any headphone/IEM I tried.
Interference: None
Summary: With the form factor similar to the Stepdance, an internal 9V battery with an internal charger and better battery life the V2 is a great performer for the price.  If you use high sensitivity IEMs make sure to get the logarithmic volume and have Neco set the gain lower (mine is standard gain).  For dynamic driver IEMs or headphone this shouldn't be an issue.  While the V2 isn't quite a giant killer, it is a giant in its price range. 

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Manufacturer: Quables
Model: iQube V2
Price: $699
Product notes: Class D amplifier
Type: Portable DAC/amp
Volume control: Analog, knob
Power connector: USB (mini B)

Battery life: (4 AAA batteries) Unfortunately I didn't have the opportunity to run the iQube until the batteries ran out, but I did use it for several hours for over more than a week before the battery needed a recharge driving IEMs.  Per the manufacturer the iQube V2 should last between 10 and 20 hours depending on the headphone/volume used, however I think I got more time out if the iQube than 20 hours.
Features/Information:
- 16 bit, 32 / 44.1 / 48K sample rates

- CS4344, 24 bit delta sigma DAC

- Gain switch (low gain = 2, high gain = 7)
Works with 4 pin headphone plugs: Yes

Sound signature: The iQube V2 is neutral through the midrange and treble with an emphasis in the bass region resulting in a warmer presentation.  Recreating a spacious and 3D soundstage, the transparency is very good letting the rest of the chain impart the sonic signature on the presentation more so than the iQube, which is what you want in your amp!  The DAC section is also very transparent and doesn't change the sound signature of the iQube.

Sound quality: The overall quality of the iQube was very good with just about everything I threw at it from the K701 to all of my custom IEMs to various dynamic driver IEMs/ear buds I have lying around.  There is no lack of power in the bass region, but with the bit of enhancement the iQube sounded a little less controlled in comparison with amps such as the Stepdance and Cruise.  Dynamics are good and near the top of the performance curve, but not the best both as an amp and as a DAC.  Resolution and clarity were also very good, but not at the top of the performance curve. 

Paired with my high sensitivity custom IEMs, lead by the JH16 and LS8, the iQube did a good job but there is hiss and a slight channel imbalance at lower volumes.  Pairing is dependent on the sound signature of the custom IEM, but in general there were no bad matches and the iQube was at or near the top of the performance heap.

When coupled with the LCD-2 v1 the iQube did a good job, but not great, however no portable amp compared with the Anedio D1 desktop DAC/amp.  The K701 sounded spacious and had plenty of bass with good control, resulting in a musical combination the combines the strengths of both the amp and the headphone.  Combining the what the iQube does well it performs quite well overall as both an amp and a DAC.

Note: After my listening I read other reviews of the iQube V2 and for some reason I seem to hear the V2 differently than other reviewers as the bass was more emphasized and in comparison with the other amps in this review, specifically the Stepdance, D10, Cruise, uHA-120, and Pico Slim, the iQube sounded on the warmer side of neutral and didn't have quite the bass speed or control.  The differences were smaller with lower resolution headphones, but still there to an extent.  

Channel Imbalance: Yes, with the JH16 at low volume levels, but not an issue with the majority of my custom IEMs and not an issue with headphones.

Hiss: There is slight hiss with the JH16, and the hiss is constant and does not change with the volume.
Interference: Setting my Blackberry on the amp or within about 8 inches resulted in some noise.  My iPhone 3G did have interference when connecting via wi-fi, but that was reduce a good deal when I switched to 3G service.  The iPhone didn't interfere with the amp when it was 1.5" or further away.
Summary: The iQube is a very nice amp that does many things right and nothing really wrong.  The combination of amp and DAC come with a space premium resulting in a portable amp that isn't all that portable, or at least pocketable.  But if you do want to bring it along with you the results will be great sound from either a computer or another source.  The amp section is very good but not the top performer despite the highest price, although not technically that far off.  The DAC section is high quality and does not alter the performance of the amp vs. when used via line-in from higher performing DACs such as the 801 or D1, although the DAC doesn't have the resolution of those two, but depending on the headphone used, track, and bit depth, the DAC differences are not very large. 

Taking into account the overall performance of the iQube vs. the competition, it is a very strong performer.

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Auzentech i.Fuzen HP-1 iPhone 4/4S amp case

Manufacturer: Auzentech
 

Model: i.Fuzen HP-1
 

Price: $129
 

Product notes: iPhone 4 & 4S case amp with built in battery
 

Type: iPhone 4/4S case amp
 

Volume control: digital, touch buttons
 

Power connector: USB (mini B)

Battery life: Using the battery for the amp, the i.Fuzen easily outlasts the iPhone.  If used as a backup battery the i.Fuzen was able to maintain the iPhone charge and play for at least 8 hours while still having 2 to 3 bars of power left, depending on how much data/voice was used. 
 

Features:
- Low and high gain 3.5mm output jacks

- Can be used as a battery for the iPhone
 

Works with 4 pin headphone plugs: Yes

Sound signature: More laid back than the iPhone 4S headphone out with a more spacious presentation that doesn’t lose the presentation depth.  Due to the more spacious sound, the imaging and apparent detail levels are higher.
 

Sound quality: Depending on the headphone used, the technical improvements vs. the iPhone 4S range from small to significant.  The 4S sounds good, but lacks resolution and doesn’t control the drivers all that well when there is lots of bass.  While the i.Fuzen has a higher resolution with the 4S, the difference isn’t all that large, but what does improve is the control and clarity of the presentation.  It is due to the improved control, larger space, and laid back in comparison presentation making the details stand out more with better articulation.   It is difficult to compare with my other portable amps due to the form factor except with an iPhone, but the i.Fuzen keeps up with more expensive amps.  One potential issue is the digital volume steps with ultra sensitive custom IEMs as the JH16 on the lowest volume setting was quite, but not as quite as I would listen to if I wanted to fall asleep with the JH16.  But that is not a big issue for on the go since there is usually always background noise.

I used the high gain headphone jack (the one with two dots) with the K701 with very good results.  First, the K701 sounds very bass light from the headphone out while the i.Fuzen adds a good amount of body and depth to the bass.  Dynamics and depth of the presentation are improved resulting in a more natural and open sound.  During my testing I was distracted and after a bit I was thinking the sound was pretty disappointing and I noticed I was connected to the iPhone HPO and when I switched to the i.Fuzen I immediately noticed the quality improvement.  The i.Fuzen can drive the 701 much much louder than the HPO from the high gain jack as the first step up in volume is equivalent to about 45% volume from the iPhone HPO.

I also had a short audition with the iPhone 4 and the i.Fuzen HP-1 with a similar result of hearing an improvement, however the improvement was different.  While it was short, it sounded like the resolution was higher with the i.Fuzen and of course there was much more driving power and a slightly fuller, warmer sound.

Channel Imbalance: No

Hiss: None

Interference: None

Summary: The i.Fuzen is a great design and to my knowledge, the first amp built into a phone case.  The case doesn’t add much bulk to the iPhone 4/4S and is surprisingly light, but it the length it does add can be an issue for those with small pockets.  The added battery helps with iPhone life while powering the amp.  With performance that is an improvement with both headphones and IEMs, the i.Fuzen could turn your iPhone 4/4S into a high performing player both on the go and at home.  With a size increase that is much smaller than even the Pico Slim, the i.Fuzen offers a very strong performance for the size, and combining the price, it also excels in that area.  I have seen beefier cases and cases that provide less protection for the iPhone and the i.Fuzen does offer good protection and should prevent damage from most drops.  Overall with all things considered, Auzentech did a great job bringing this product to market, giving iPhone users something they can use to boost audio quality without adding too much bulk or wallet drain.

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Manufacturer: Furutech/ADL
Model: Cruise
Price: $475
Product notes: The Stride is available without the carbon fiber for $350.  Had issues with the fit of a Via Blue connector on an interconnect cable as the plug was nearly too large to fit in the jack.
Type: portable DAC/amp
Volume control: analog, dial
Power connector: USB (mini B)

Battery life: 80 hours (manufacturer spec).  I never ran out of battery life while using the Cruise.
Features:
- Auto-circuit disconnect when the headphone is not plugged in resulting in no audible noise and a 2 second delay before music starts playing

- Internal DAC, 24/96 USB
Works with 4 pin headphone plugs: Yes

Sound: With a very dynamic sound, the Cruise is spacious, punchy and exciting with a great sense of speed.  The brighter sound along with a slightly thinner note than the competition brings with it great detail and resolution as well as excellent imaging and transparency.  While the Cruise is on the brighter side in comparison with the amps reviewed here, it still has excellent deep bass and seems to slightly enhance the lowest octaves of the music.  With genres such as psy-trance and speed metal the Cruise has a speed advantage over other amps, and with genres such as live instrumental performances the Cruise can really bring out the details in the instruments and show top notch imaging. 

The Cruise isn’t the be-all end-all amp however as the hiss is noticeable upon first listen with many of my high sensitivity IEMs, however after a bit of time I don’t notice the hiss, well, unless I am focusing on the music and there is a gap between tracks or a quiet area of a song.  I was expecting a black background, but even though it doesn’t have one I still want to listen to the Cruise because of the rest of the presentation.  The most annoying thing for me, however, is if my phone is too close to the Cruise I will hear static and noise when the phone radio turns on.

Powering full sized headphones such as the LCD-2 and K701, the Cruise does well with plenty of power even though there is no gain switch.  Of course, none of the portable amps I have heard can make the LCD-2 sound as good as a desktop amp, but it does rank in the upper performance levels with the LCD-2 for a portable amp, and without the hiss issue.  The K701 sounds excellent from the Cruise with great detail, air and space.

Channel Imbalance: Yes, but barely audible with high sensitivity IEMs

Hiss: Yes, there is a continuous low level hiss with high sensitivity IEMs. 
Interference: Yes, some clicking with the iPhone 3G and some static/noise on the right channel with my Blackberry.  Phones must be 6” or further from the Cruise. ** Now fixed per Furutech.
Summary: While the shape isn't typical, it can still easily be strapped to your device and the carbon fiber finish of the Cruise looks stunning; it is the best looking amp I have seen (my pictures don't really show just how great it looks).  From a sound perspective it is difficult to fault the Cruise, but be prepared for a brighter sound to go with oodles of dynamics that lead to a punchy and fast sound.  The DAC section is as nice as the amp is, comparing similarly as to how the amp section performs.  Unfortunately with higher sensitivity custom IEMs there is a hiss present at all times, although it is not at a high level.  

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Manufacturer: Just Audio

Model: uHA-120

Price: £199.86

Product notes: AHA-120 is the class A variant; Justin owns Just Audio and is not only personable, but very meticulous about his products. 

Type: portable amp

Volume control: analog, knob.  There is a volume pot upgrade that is more balanced at low volumes.   Justin has improved the grading for the standard volume pots which will give better balance results. 

Power connector: USB

Battery life: Up to 24 hours per the manufacturer

Features:
- Normal or fast charging - normal is for lower powered USB ports

- APSS (auto or battery) - when set to USB, the uHA will take power from the USB input vs. the battery, with more power output (28 mW @ 300 Ohms vs. 16 mW @ 300 Ohms when set to battery

- Adjustable gain via internal jumpers: 12 dB or 6 dB; tool and instructions included and Justin made a program that allows you to calculate the power output.

Includes: Tool to open the uHA-120 so you can change the gain

Specifications:

Maximum Continuous Power output:

                60 mWrms/channel into 32 ohm load (120mWrms total);

                28 mWrms/channel into 300 ohm load;

Distortion (THD+N): < 0.005% @ 1KHz (-16dBu to 5dBu output level)[1];

Dynamic range (dBA): 110dB

Bandwidth (-1dB): 10Hz-40kHz

Output impedance: < 1 ohm [2]

Output current limit: ~= +/-80mA per channel

Maximum Gain (REV B): 12dB || 6dB (based on jumper setting);

Battery recharge time (max): 2.5 hour fast charge; 6 hour normal charge;

Dimensions (approx): height=23mm; width=52mm; length=85mm

Weight = 125g +/-1g

Notes

[1] Tested using Beyerdynamic DT-311 (32 ohm) headphones;

[2] Actual measured output impedance < 0.1ohm; BW = 10Hz-40kHz with 2R2 load (100mV test level).

You can go to the specifications on the Just Audio site for charts.

Works with 4 pin headphone plugs: No

Form Factor: The uHA-120 uses a similar form factor to the Stepdance and Neco amps.

Sound Signature: I have spent much time thinking of what to write here, unsuccessfully and realized that the uHA rather just disappears.  It is very neutral and unobtrusive in sound, imparting less of a sonic signature on the music than just about all the other amps I have tested.  There is still a slight bump in the bass and treble with a little touch of warmth and a smooth presentation, but overall the uHA-120 is very neutral.

Sound Quality: The uHA stacks up well in the comparison, not giving the best performance, but not being outclassed with an overall sound quality score that is in line with the Pico Slim.  With great clarity, good resolution, and very good transparency delivered with a smooth and very enjoyable presentation I often forget about the uHA and just focus on the music I am listening to or headphone I am reviewing.  While I do forget about the amp, it doesn't give the liveliest presentation and is a bit below many of the other amps I have tested in soundstage width.

With headphones, the uHA has the least amount of headroom, however I did not adjust the internal gain, so the ability to play loud will improve.  However, the uHA did hold its own with headphones at volume levels I would listen at, which isn't all that loud.  The biggest issue is with high sensitivity IEMs, especially my custom IEMs as the uHA I have for review does have a fairly significant channel imbalance, not allowing me to listen at my typical quiet volumes except with a source that has its own volume control.  And the uHA doesn't pair well with every source, as with my modded iPod the uHA doesn't seem to perform as well as from the line out of the 801 or TTD V2.

Channel Imbalance: Yes, fairly significant with high sensitivity IEMs and mild with lower sensitivity IEMs.  No problem with most headphones.

Hiss: Not for typical use as there is hiss as the volume increases, and with the JH16 it was only evident at levels that are much too loud for any extended period of time.

Interference: No interference from both my Blackberry and my iPhone

Summary: The uHA is a capable performer that doesn't add anything to the signal path other than what it should: more power and control.  The transparency is very good as the uHA disappears and isn't noticed like other amps are, but the other amps get noticed for adding dynamics and punch, or giving a brighter or warmer sound, or even adding space.  The biggest issue with the uHA was the imbalance with high sensitivity IEMs, even on low gain.  There is an option for an upgraded volume pot, and I would like to hear that option some day.  I did often forget that the jack is not 4 pin compatible when used with something such as the Fabs.  All in all, if the balance issue was not present, the uHA would be a great amp for the price for IEMs.  As it stands, it is a very nice amp for headphones and a great, neutral choice that will allow you to experience your other equipment without concern of your amp adding its signature to the chain.

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Manufacturer: Portaphile
Model: 627

Click on an image to enlarge

Click on an image to enlarge

Sound: Upon first listen with a BA CIEM, the O2 sounded quite good.  Switching to headphones, the HD600 specifically, I was impressed.  The O2 was performing well some issues came to light, especially when I started comparing it with some higher priced amps.  Notes are a little soft both on the attack and decay which results in a slightly slower sound with dynamics that aren’t quite up to par with most of the other amps I have.  This note thickness and the dynamics have a trickle-down effect on the realism and transparency as the headphones didn’t disappear quite as much as my other amps except the similarly priced Neco.  The spaciousness of the O2 is good, better than some more expensive amps, but the imaging is slightly below average (of more expensive amps), which seemed to be due to the attack/decay.  

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Manufacturer: Shonyun

Model: 306

Price: $180 on ebay

Product Overview: The amp is on the larger side for a portable amp as it is larger than the Neco V2, especially in length, but slightly smaller than the EHP-O2.  The body of the unit uses an anodized brushed metal finish that looks nice but does scratch relatively easily.  The face plate looks great and is finished much better, and the volume knob is solid.  The 306 uses two AD8397ARDZ (with a high slew rate, high-bandwidth), Japan KOA high precision metal film resistors, WIMA capacitors, ELAN fever electrolytic capacitor, KOA metal film SMD resistors, and has five built-in 3.7V lithium batteries to stabilize operating voltage.  There is a single input and single output on the front panel.

Size/Weight: 110mm * 70mm * 25mm
 

Type: Portable amp
 

Volume control: Analog knob
 

Power connector: Wall adapter, non-standard (24V)

Battery life: Approximately 12 hours

Features:

- Frequency response:10-100KHz

- Output power: 120mW

- Signal to Noise Ratio: 105dB

- Distortion: <0.005%

- Charging adapter: 24V-500mA

- Suitable impedance: 16 ~ 300Ω

- Input impedance: 47KΩ

- Output Current: 600mA

Works with 4 pin headphone plugs: Yes

Sound: The 306 is a fairly neutral amp, with a bit less bass weight and a slight bit more treble than the two competing amps I have in the price range, the EHP-O2 and Neco V2.  The 306 is typically more natural sounding in the treble region, however the overall performance relative to the other amps does vary with different headphone pairings.  One of the largest differences between the 306 and other amps in the price range, including the uHA-120 is the refinement of the presentation, which is quite good for the price. 

Comparing the amps with headphones, dynamic driver IEMs and the EarPods, the 306 had slightly less control of the bass driver even though the presentation had the least amount of bass in comparison.  Moving up from the bass, the 306 was more refined at times depending on the headphone.  The 306 has plenty of power to drive headphones, but it doesn’t drive power hungry headphones such as the LCD-2 all that well, which is no different than most portable amps, even those that cost well over double. 

The better the source, the better the 306 will perform, but it does better with lower quality sources such as the iPhone 4S than the EHP-O2 and most of the time the V2.  As you go up the source chain, the 306 can reproduce more detail and present a larger space and has an overall more refined presentation than the other amps.

One of the difficult things in comparing amps is performance differs depending on the headphone and source paired with them, making the chain very important.  I have included the 306 in the source matching section of several of my CIEM threads, which might help with some reference points.

I tested the 306 with the HD600 and AKG K550.  With headphones there are is no hiss like there can be with my CIEMs.  The 306 does extremely well with both the HD600 and K550, controlling the low end quite well, recreating very good space, and articulating detail.  Compared with the uHA-120 (low gain mode), the 306 controls the bass better, which has a trickle-down effect making the rest of the spectrum cleaner, and the soundstage is a bit more expansive.  Compared with the O2, the HD600 sounded more dynamic and more forward, but control was similar.  With the K550, the bass was equally controlled, but the rest of the spectrum was smoother with the 306.  The Stepdance is a bit brighter than the 306, but the treble is also not quite as smooth as that of the 306, however the overall sound from the SD is a bit more natural sounding.  Moving to the HD600, the SD is still a bit more natural with more depth to the presentation, but the differences aren’t huge.  Note that I had to use an adapter for my 1/4” to 1/8” adapter due to the recessed plugs in the 306.

Channel Imbalance: Yes, with moderate sensitivity IEMs at lower volumes; more severe with higher sensitivity IEMs and at very low volumes.

Hiss: Yes, with high sensitivity IEMs.  Hiss increases as the volume is increased.
 

Interference: None
 

Summary: The Shonyun 306 is an extremely refined amp for the price range and has a lighter, leaner sound signature.  There is a balance across the frequency spectrum, but the bass isn’t quite as prominent as with the Neco V2 or EHP-O2, however the imaging is better than the other two.  Depending on the source and headphone matchup, the 306 can be a fantastic performer for the price point.  It is larger than many other portable amps, but smaller than the EHP-O2 and slightly larger than the Portaphile 627.  The 306 is recommended due to the refinement, smoothness, imaging and natural sound, but be sure you are OK with a slightly lower bass presence than other amps in the price range, slight channel imbalance at low volumes, and hiss with high sensitivity IEMs.

When used with headphones, at least the ones I tried, the 306 was quite impressive and is definitely worth the price.  The open sound and controlled bass work well and there is plenty of power for headphones.  You can do better at higher prices, but the differences with the HD600 and K550 weren’t huge to me.

Reserved

Thank you, what is your price range, source, and headphones?

Quote:

Originally Posted by AyeCee 

 

source: ipod nano 3g

headphones: sennheiser HD25-1 ii

budget: $150 tops

The HD25 isn't all that difficult to drive so that price range should be OK.  There are some good options and the Neco V2 I have is great for the price.  I will also be testing an Epiphany Acoustics EPH-O2 and a Mini 3, but at the moment I can highly recommend the V2.

Quote:

Originally Posted by BleaK 

wow, this looking to be a great thread!

Thanks!

I thought so also, but it works as there is no problem as a desktop amp and for use with my iPod it is fine.

i.Fuzen review completed (the last review in the first post)
 

Quote:

Originally Posted by estreeter 

Looking forward to your thoughts on the uHA-120 - keep up the good work.

Thanks, I will be working on it in the near future.

Quote:

Originally Posted by esanthosh 

I missed this thread until now.

 

Is it possible for you to get a loaner of Arrow 3G, 2StepDance or UHA-6S? I would be very interested in knowing what you think of them :)

As time goes, I plan on updating this thread with more amps, but I need to finish these reviews first.