Pros: Very clear, liquid mids, exciting highs that don't go overboard, good control in the bass region
Cons: Bass impact is somewhat soft, unit is large and heavy, and gets fairly hot, recessed input/output section is frustrating
In my review of the Shonyun 301 Pro desktop amplifier, I gave it high marks for sound quality but noted some issues in terms of build quality. I also felt that the price was somewhat ambitious considering that Shonyun is a newcomer to the HeadFi scene. Still, it's a rather enjoyable amp that I continue to use and appreciate on a regular basis. It sounds especially good with the latest LCD-2 which I recently acquired.
Shonyun doesn't merely offer one amp but rather has three different models. The 301 is their desktop offering, and the other two are portable units - the 303 and the larger 306. The 306 sells for around $170 and is the focus of this review.
When I say larger, I don't just mean "relative to the 303 model". This amp is large by any standard and for me approaches the upper limit in terms of what I'm willing to carry around. Including the volume knob, the 306 measures over 5 inches long, nearly 3 inches wide, and about an inch thick. That may not sound like much but check out some of my comparison pictures to see how it looks next to other portable amps. The weight is significant too - at 260g it weighs approximately twice as much as the Audinst AMP-HP, and the Audinst isn't even what I'd consider an ultra-compact amp.
The build quality of the 306 is far more in line with its price class as compared to the Shonyun 301. It won't necassarily win any beauty contests but neither is it what I'd call ugly, and my unit is free from any issues like channel imbalance. Overall I'd say this is a well made amp and seems tough enough to withstand the inevitable abuse a portable amp would be subjected to.
The design is simple: front panel 1/8" input and output. Volume knob which "clicks" when turned all the way off, thus doubling as a power switch. Rear panel charging port for the included wall wart. Nothing really new and exciting here. The only potential issue I can see is the way both 1/8" jacks are recessed somewhat too deeply into the face. This causes some issues when using certain cables - I had several instances where I thought I had a snug connection, only to note distortion one one channel while listening. Turns out my connection was not quite in deep enough due to the recessed socket. I really don't know why they would have bothered to make it this way, knowing the issues it would cause. Perhaps the designer thought it looked good and didn't test it against a wide enough range of headphone cables.
The 306 is based around a pair of Analog Devices AD8397ARDZ opamps. These twin 2-channel opamps are stacked in a gain+buffer configuration and biased into class A. Shonyun never really specifies the amount of bias but judging from the battery life (roughly 10 hours in my experience) we are pretty far into class A. The other clue indicating class A operation is the build up of heat - this thing gets fairly warm to the touch just 15 minutes of use. It's not too hot to hold but I don't know how comfortable it would be in a pocket. Not that the size of this amp lends itself to pocket use... but you get the idea. I'd say that the weight, size, and heat all conspire to make this somewhat more of a transportable setup than a true portable.
I tried my best to get a good internal picture of the unit but, as with the 301, Shonyun made it difficult. The full thing just wouldn't come apart without some potential damage. They also cover most the output section with some blue material, so it isn't visible. I can't imagine what purpose that serves other than to stop some other company from stealing their design - as unlikely as that sounds. I suppose could have sliced off the blue stuff and had a look but I got lazy. So no internal pics on this one, sorry.
In terms of output, Shonyun lists the 306 as delivering up to 455mW at 16 ohm and 120mW at 300 ohm. They don't list the other increments but if things behave in a linear fashion we can assume roughly 300mW (give or take) for most IEMs and low impedance headphones such as Grado, Audio Technica, and Denon. That's fairly powerful. I notice that Shonyun claims these as measured results rather than merely published numbers. A lot of companies just list the specs from the opamp used in the output stage and call it a day. When measured, the results are often rather different. For example - my iHiFi812V2 uses the same AD8397 in the headphone stage, and measures similarly with low impedance loads. Yet it drops down to 50mW at 300 ohms - less than half what the Shonyun can provide. I'm not necessarily saying one unit sounds better than the other, merely pointing out that a lot of specs listed for these types of items are misleading, and I appreciate when companies like Shonyun and iHiFi post accurate numbers based on real world measurements.
I used the Shonyun 306 in both portable and home situations.
On the go, I mostly fed it with the previously mentioned iHiFi812V2. I also made occasional use of my iPad with a CablePro Freedom series line out dock. On the go listening was done with the Heir Audio 8.A and 6.A LE, as well as the JH13pro FreqPhase, Lear LCM5, Earproof Atom, 1964 V3, Aurisonics AS-1b, and V-MODA M80.
At home, I mostly used the same iHiFi source (for consistency) but this time around used the 306 to drive some full sized headphones: Audio Technica AD2000 and W1000X, Lawton LA7000, HiFiMAN HE400, Sennheiser HD650, Ultrasone Signature Pro, Beyer T1, Audeze LCD-2, and Smeggy Thunderpants. A 1/4" to 1/8" adapter, again from the CablePro Freedom series, was used to connect these headphones to the 1/8" jack of the 306.
The Shonyun 306 has some similarities to the desktop 301pro model in that they both have a somewhat-more-lively-than-neutral sound. But I wouldn't call it a clearly defined Shonyun "house-sound" as they each take their own path towards liveliness. The desktop model is a bit on the warm side with a fair amount of excitement and sparkle (but not too much). The portable 306 isn't quite like that, but it's still pretty good in its own right.
The key difference is in terms of bass response. The 306 unit seems to have fairly tame low end response. It's not rolled off - on the contrary it extends nice and deep. It's just somewhat mellow in the mix compared to my other portable amps. This means somewhat less engaging results at times: this is not my favorite amp for music like metal or trance. On the other hand, it does quite well with most rock, jazz, and classical. The bass that is there is clean and punchy with a nice sense of realism. It's very well controlled too, and helps even out the response of some overly bass-heavy mixes.
The 306 is quite happy in the midrange section. It's got a very involving presentation that reminds me of various tube amps I've owned - specifically my old DarkVoice 337SE. Not that it is exactly on the same level but they both portray a sense of ease and liquidity that is rather hard to find from other amps. If you love vocals, this amp is definitely a good match. It also excels at capturing the snap of a snare drum and is actually very dynamic if we disregard the slightly soft bass.
Highs are an area where I sense the most similarity to the desktop 301 unit. Both have just the slightest bit of added sparkle which can be very exciting at times but also fatiguing with some recordings or headphones. To my ears this is definitely not a Grado amp. Yet I did enjoy it with the Audio Technica W1000X and AD2000, both of which can at times be considered bright. So I guess it's a case by case situation. I have heard portable amps with better extension up top but they tend to cost significantly more than the 306.
One thing I didn't care for was the background hiss, which could be unacceptable with certain headphones or IEMs. I ended up not using the JH13pro at all because the hiss was too distracting. Same for the Ultrasone Signature Pro, which was otherwise a very good match in terms of sound signature. The Lear LCM5 hissed a lot by itself but sounded very clean using the Monitor Tuned Adapter (which raises impedance up to around 180 ohms). That was an enjoyable combination - very slightly on the bright side, but incredibly fast and very detailed, almost like a Stax setup. The Earproof Atom (70 ohms) sounded very crisp and clean and also managed a nice black background. The 1964 Ears V3 had some hiss but was still tolerable, as was the Heir Audio 8.A and 6.A LE. The Aurisonics AS-1b was a spectacular match due to the dark sound signature, but it had a bit more hiss than I'd like. If not for the hiss the 306 would be my favorite amp for the AS-1b.
All is not lost though, as the 306 plays very well with full size cans. Remember that whole bit about being class A and having fairly high output? That means it drives most big headphones with the level of authority usually reserved for home units. The HE400 and LCD-2 sound about as good as I've heard for under $200 worth of amping. Have I heard them sound better? Of course. But never from an amp this small and inexpensive. The slightly subdued low frequency performance is offset by the mighty impact of these planar models, and the overall result is very pleasing. I also liked this amp with the Lawton LA7000, where it gave clarity to the mids and yet didn't overdo the highs. The Beyer T1 is not an ideal match though, sounding somewhat on the thin side and making vocals come off as overly nasal. The HD650 is a respectable match, as is the Smeggy Thunderpants. Overall I'd say keep away from brighter headphones and it will typically sound great.
Again, Shonyun impressed me in some ways and leaves me scratching my head at the same time. The size of this amp is bordering on too large for my taste, but I know others who wouldn't mind. Yet it's the heat that really makes me question its utility in a portable situation. I just don't think people would like carrying an amp this warm while commuting. The hiss makes it less than ideal with a good number of armature based IEMs, and that recessed front panel just baffles me.
Still, despite all that, the amp sounds really great with most of my full size headphones. I'd say it is better than most portable amps I've heard, and in my collection is only beaten by my favorite amp, the Leckerton UHA-6S. If someone was in the market for a transportable unit that could pair well with some of their more difficult headphones, I'd say the Shonyun 306 is worth a look. Hopefully Shonyun continues to refine their designs - they have the sound thing down but seem to struggle with other aspects of their designs. If they focus on usability and build quality, their next round of products could be something to look out for.