Synergy
Pairings
If you are the type of person who believes that DACs do not make a difference the SMSL SH-X can prove you wrong in the sense that it can easily reveal each DAC’s nuances and intricacies.
For example, if you connect an iFi Audio NEO iDSD 2 or their ZEN One Signature DAC and feed the SH-X with either you get a clear picture of the Burr Brown and iFi Audio’s touch of warmth.
When I used the HYMALAYA R2R equipped HIFIMAN EF600 DAC section, one can also detect the overall warm vocalization, full bass response, and a tall soundstage presentation.
When you use the SH-X and SU-X combo, the bass tightens up, vocal clarity is brought forth and the high frequencies present themselves with utmost clarity.
However, those are the traits of the DAC’s performance but it does demonstrate that the SH-X has the capability of translating those characteristics and satisfyingly delivering them to your headphones.
Power
My trusty HIFIMAN Sundara and Arya Organic were two of the headphones I mostly used with the SH-X and SU-X combo.
The Sundara gained more performance over the Organic’s efficient design which is funny. However, the Dekoni Audio Blue benefitted the most even though the single-ended section was the only option available for the Blue.
At 0 gain, the single-ended output can drive my second-generation Hifiman Arya with plenty of volume headroom to spare enough for two more sets, so imagine on the balanced side. It is overwhelming in the high-gain setting.
The high gain on the single-ended side certainly powered my Dekoni Audio Blue set and the medium setting with volume to spare. I do not think there is a headphone commercially available right now that can not be driven by the SH-X.
At the bottom gain and using the lowest power-producing port, this amplifier does not seem to lose any dynamic energy, which is noteworthy. And the upper settings? Well of course not.
Select Comparisons
Topping A90
Technical
One of my favorite amplifiers has been the NFCA module-equipped and smaller-statured Topping A90 headphone amplifier because of its high power, undistorted output, and flexible I/O along with preamplifier capability as a bonus.
Although the A90’s available power output is lower on average at 7.6 watts, it manages to hit a higher number in other areas, for example, 145 dB versus the SH-X’s 137 dB for SNR. But one cannot notice much because the A90 has a softer demeanor for sound production.
The A90 has identical connectivity options on the front and the rear panel. The same dual IO is also included. This consists of two 3-pin XLR balanced connections and a set of RCA plugs.
Both models have a three-gain stage that accommodates IEMs with enough power for demanding headphones. What I find a coincidence is that both these models post identical 0.0006% distortion levels.
Design
The A90 has a busy front panel considering the SH-X’s simplistic approach design which is also more industrial-like in appearance. There is more to do upfront on the A90 but there is no remote control capability.
The A90 relies on mechanical switches for input selection and gain selection. There is a third switch upfront that slips the A90 into preamp mode. The SH-X relies on digital control for all these features and includes a longer list of features to boot.
The A90 also comes in two color schemes, black and silver. The lack of a remote? If you are like me, a desktop user, then you might not need remote control capability since you can always reach out and touch the unit and physically make adjustments.
I do like the feel of the A90 volume knob more because of the small amount of play within the shaft of the SH-X ‘s volume control. It does make up for it by implementing a step relay switching type with one hundred steps of adjustment.
Performance
The SMSL SH-X is the hotter unit all around. What I mean is that the volume control on the A90, for example, takes a lot of turning to get to a high volume level but not the SH-X which raises the volume in a rather linear fashion but rises quicker in overall volume.
Speaking of hot, the cabinets are night and day because the SMSL SH-X runs hot and has that protection quirk where you have to give it some time for the cabinet to cool down.
It does it more so with certain cables but the positive side of this type of implementation is that the unit provides effective protection.
You can also consider the line-out section area of the SH-X to be hotter with a higher output voltage. This seems to be a fixed out with no adjustment possibilities.
Both amplifiers portray a neutral, balanced frequency response. However, I would characterize the A90 as the amplifier with a softer demeanor versus the SH-X’s sometimes aggressive approach, particularly in the vocals and midrange of the tested headphones.
HIFIMAN EF600
Technical
I was curious to see how this AIO could stack up to a separate headphone amplifier and it did well so I proceeded to write up a comparison although these two models fit different scenarios and are considered apples and oranges.
The EF600 uses a HYMALAYA DAC, however, more importantly, it has a well-designed power stage that reminds me of the one used within the SU-X that employs a large Toroidal transformer alongside large capacitors.
The EF600 power amplification section is rated at around five watts per side. However, it has a juicy power section behind it and can improve on dynamics and overall noise levels which seem to be negligible on both these models, especially on their low gain settings.
Design
The EF600 tower design was designed to accommodate the headphone stand-shaped case which is a novel idea used by only a few amplifier makers. However, beware of the heat that although dissipated from small vents on top can heat the top where and cause headband deterioration. I advise using it as a stand when the unit is turned off.
The HIFIMAN EF600 sports a heavy cabinet made from a thick sheet of aluminum, folded into a U-shape, and fitted with a polymer shell. It is a heavy cabinet, well made, but it can only be placed vertically.
The only aspect I dislike is the volume control which looks like a stove knob plus it has lots of play in the shaft. I much prefer the SMSL implementation.
The bottom of the EF600 is fitted with a large toroidal transformer. I feel SMSL should have explored the same implementation since the accompanying DAC, the SU-X has a similarly implemented power section, but not the SH-X.
Performance
I have to admit, it is a close fight. However, the SH-X stands out due to the extra power. The soundstage presentation is wider with a more panoramic quality in general. The vocal presentation within the EF600 seems introverted over the open-airiness of the SU-X.
The HIFIMAN EF600 amplifier section does width and height well but there is an extra layer of depth, especially within the frontal stage when you listen to the SH-X.
What makes the EF600 special is the HYMALAYA R2R DAC section that supplies the amp section with that missing width and expansiveness in vocals one gets from the SU-X DAC section. Plus, it is a musical DAC that produces nuances unheard of in this class until now.
The HIFIMAN does produce a fuller bass and has a slight increase in bass presence over the SMSL’s clean approach that opted for a speedy and lean bass presentation.
The warmer set is the EF600 combo but the overall fidelity is an obvious leap in natural timbre, speed, and cleanliness when you step up to the dedicated SH-X amplification section.
My Verdict
The SMSL SH-X is a musical-sounding muscular amplifier that veers away from an analytical character and instead offers up a natural timbre with an elevated level of detail retrieval and a great dynamic response overall.
The SH-X is a piece of gear to have around when you want an unrestrained performance but it’s not an all-day use component since it doesn’t have auto standby and does develop a toasty internal temperature. But this amplifier is all in on sound quality.
If you are looking for a great opamp-based headphone amplifier, there are not many examples today that can surpass it at this asking price. Sonically it is my kind of amplifier. It is powerful, clean, speedy, with excellent staging capabilities, and above all else, musical.
SMSL SH-X Technical Specifications
- Inputs: Balanced, Unbalanced
- Headphone outputs: 4.4mm, XLR balanced, 6.35mm unbalanced
- Pre-outs: Balanced, Unbalanced
- Output power: 11.5W @ 16Ω, 5.5W @ 32Ω, 600mW @ 300Ω, 300mW @ 600Ω
- SNR: 137db
- Dynamic range: 137db
- THD+N: -123db, 0.00006%, (1kHz @32Ω)
- Input impedance: 32kΩ
- Amplifier output impedance: near 0Ω
- Pre-out impedance: Balanced 66Ω, unbalanced 33Ω
- Frequency response: 20Hz to 100kHz -5db
- Gain: Balanced low-2db, mid+6db, high+23db, Unbalanced low-8db, Mid 0db, high +17db
- Power consumption: ≤50W
- Power standby: ≤5W
- Size: 250 x 51 x 192 mm
- Weight: 2.4kg, 5.33lbs
