In today’s review we are talking about the headphone amplifier SMSL HO100 . It is a compact and affordable desktop device capable of delivering up to 3W of output power.
When looking for an amplifier, even a budget one, you’ll have a lot of choice these days: Chinese audio manufacturers like SMSL produce a wide range of devices with plenty of competitive features.
Our recently reviewed SH-6 amplifier is already $120 if you need single-ended amplification. But the HO100, which costs a little more, is a more powerful balanced amplifier, included in the same line as the more powerful HO200 with a preamp.
Not to be left behind by its peers, the HO100 has enough specifications and performance figures to interest those looking for a modestly priced but good-looking headphone amplifier.
Key Specifications
Since the development of its amplifier section, SMSL has been committed to bringing low distortion and flat frequency response sound to the masses. The HO100 is no exception with its extremely competitive 0.00006% THD+N rating as seen in SMSL’s latest releases.
Up to 3W of pure power can be used for 16″ monitors and 1.5W for 32″ headphones. Moreover, the presence of a low gain setting of -9.5dB for sensitive CBs and +15.5dB for hungry pairs, on top of the default 0dB average gain, makes the HO100 quite versatile and easily compatible with most devices.
SMSL also included an ultra-low noise power supply and used high quality relays. The HO100’s splash-free design will appeal to those who prefer to leave their more sensitive headphones connected.
Design
Finished in black, the HO100’s understated yet elegant design allows it to be as user-friendly as possible in an entry-level package that delivers on both form and function.
Weighing in at 560g, the HO100 is lighter than it appears at first glance, and a few firm presses on the aluminum body draping around the front and back panels create a tight feedback that enhances its durability.
Even though the tempered glass panel is the main design element of the façade, it easily attracts fingerprints, making it a constant task of cleaning every now and then.
The distinctive feature of the switches used by SMSL is their crispness and precision, which is the opposite of the rubbery turn of a volume control.
The 4.4mm and 6.3mm gold-plated headphone jack fittings protrude slightly and do not sit flush against the glass. Meanwhile, the RCAs are positioned vertically and are not color coded to red or white, but are correctly labeled by channel.
Input/Output
Designed for personal listening, there is no rear output except two ways to connect to the amplifier: balanced XLR and single-ended RCA.
For those who want to make the most of the HO100’s balanced input, it can easily be used by the matching SMSL DO100 DAC.
There is a 4.4mm jack on the front panel along with a standard 6.3mm jack for greater compatibility. While some may miss the 4-pin XLR for connecting headphones, the selection of outputs from SMSL is more than sufficient for most cases.
Control
Connecting a device triggers the relay and puts the device into standby mode, as indicated by the red light under the leftmost switch for turning on the device.
With all controls visible and within reach, it’s easy to check and change which input and gain level is currently selected using the remaining analog switches.
Flip the middle switch and the device is ready to use.
Flip the middle one up and the amp will use a balanced XLR input instead of an RCA one. And to suit the HO100’s varying sensitivity and power requirements, the gain can be adjusted between low, medium and high levels using the final toggle switch.
Packaging and Accessories
Similar in appearance to the packaging of most SMSL products, the HO100 also comes in a white cardboard box, the main distinguishing feature of which is the outline of the device drawn on top.
Amplifiers usually come with the bare essentials, as they are usually located at the end of the chain, so the lack of additional paraphernalia to excite is not at all surprising.
With the booklet-style user manual and paperwork out of the way, all that’s left to do is unpack the device and power cord.
The front side of the HO100 is protected by a thin film that must be peeled off to fully expose the tempered glass panel. However, the volume became an obstacle and I had to make a small cut in the plastic to get through it.
Sound Impressions
Review
Trying to get the impression of an amplifier that tries to sound as transparent as possible has shown that even on a budget of less than $200, a nice clear sound that reflects the sound of the DAC you’re feeding it with is already possible.
It immediately struck me as a faithful amp that doesn’t sound clinical or fake with details due to overly harsh highs, instead expecting a neutral presentation with a nice midrange body.
Timbre
Producing a deep and satisfying reverberation is a good feature of the HO100, giving strings and drums a full room feel. True, it sounds a little dry and at times lags behind other frequencies in volume.
While the main body of the bass has good punch during fast attacks, slower notes tend to be scattered and can feel a little congested and fat. The lack of micro-detail when playing longer notes can lead to the leveling of expected subtleties.
What sets the HO100 apart is its honest midrange tonality, allowing female vocals and instruments to retain their character with a slight lean towards boldness.
Note the harshness on softer and whisperier lyrics, which can be heard mainly on hoarse singers or worse recordings. The piano, on the other hand, is quite lively and has a lot of presence.
The transition from upper mids to lower highs, without lifting or peaking, results in moderate brightness without being loud. But if the speakers are paired with the wrong DAC, the sudden hits of horns and saxophones will be transmitted as attacking.
Cellos are quite a bright sound.
The violins stand out quite strongly from the overall picture and have no additional color, which may seem uninteresting in slow arrangements. Finally, regarding the cymbals, although they ring and are controlled, they do, however, expose some micro-details at the top end that are not transmitted.
Staging and Dynamics
SMSL interprets the width of staging for the HO100, allowing the source to speak without taking up or adding additional space. Listening to instrumental recordings recorded in the studio highlights the echoes on the walls and recreates them honestly.
While directionality and pitch are impressive, they are clear enough and easy to imagine, separation and layering are average, and on richer compositions the imagery comes too close to each other, giving the impression that some instruments are playing on the same plane.
Playing songs with a wide dynamic range is no problem. He had me completely engrossed in listening to the song with a soft intro leading to an energetic performance with a wide vocal range.
Go to page 2 below for pairings and comparison specs
Synergy
Power
With more than enough power to drive all the headphones and IEMs in my collection, the HO100’s amp section really proves its worth.
For sensitive loads, I tried Hidizs’ 18Ω MM2 IEM at low gain and did not experience any noise throughout the volume control range without music playing. Using the Focal Clear MG at medium gain, I only needed to turn up the volume by a quarter for comfortable listening.
Amplifying the HO100, I connected higher impedance Sennheiser HD560s and Audio Technica ATH-ADX5000. Even at medium gain, volume is more than adequate, with the HO100 only peaking around midday for the ADX5000 and slightly less for the HD560s.
Pairings
Despite the HO100’s transparency during the audio experience, pairing is more important to the full enjoyment of any listening experience.
During my impressions, I used the Chord Qutest the most, after first using the Matrix Mini-i Pro 3 and DO100 as a DAC. Of the three models, the HO100 opened up the most to the Qutest, appearing airy and majestic. The only minor drawback is incomplete resolution due to some limitations in the HO100’s specifications.
While the Mini-i Pro 3 came out a little bright, the official DAC paired with the HO100, the DO100 did an excellent job of reproducing clean and neutral tones, punching up the lows and mids to make them seem deeper and fuller. Although he markedly limited the scene and then continued to create smaller images.
When paired with headphones, the ADX5000’s drop-down sifted through the HO100’s deficiencies in detail extraction, however it brought a welcome lift to the body of the vocal region. In the case of the Clear MG, pairing with the DAC is very important to achieve a pleasant extended sub-bass and intimate midrange without leaving any room to breathe.
Selected comparisons
SMSL SH-8s
$229.99
Specifications
Both units have the same THD+N level of 0.00006%, using the same amplifier technology developed by SMSL. Although the SH-8s has a more powerful output of 3W@32Ω, making it more suitable for power-hungry headphones.
Limited to two gain settings: 0dB low gain and 17.5dB high gain, IEM users will have to control the SH-8s’ volume more carefully. However, output impedance won’t be an issue since it is close to zero as measured by SMSL.
The company is designed for personal use.
Designed for personal listening, the SH-8 also does not have a rear output, although the XLR and RCA inputs remain the same. And instead of a 4.4 mm jack, which performs the function of outputting a balanced signal, a 4-pin XLR is used.
Additionally, the SH-8 does not have a rear exit.
Design
For those who are into odd numbers, the SH-8 has two legs in the front and one in the back for a total of three. Several times I accidentally rocked the device, inadvertently pressing on the back corners.
There is also a difference in the toggle switches used: the toggle switch on the HO100 has a thicker shaft and a stronger latch. But the volume control on the SH-8 has noticeably less play and looks more premium.
Additionally, the HO100 does not have a glass panel.
Without a glass panel to elevate the design, the wider body of the SH-8s is a much simpler chassis with redistributed functions. Only the switch and output locations have been reversed, placing the 4-pin XLR on the very left side of the faceplate.
The SH-8 company does not have a glass panel.
Performance
Same brand, same sound? While the sound does come close as never before, with both speakers sharing the same neutrality target, where the SH-8s prove their worth is in the technical aspects.
Having a similar presence in the lower region, the SH-8 is easily perceived as having more texture and better detail. Moreover, there is a slight increase in penetration power and a crisp bite, resulting in the HO100 feeling soft.
Compared to the HO100, the SH-8 performs better.
By adding space in the mids, singers are pushed into the background and take on a calmer attack, and piano parts sound a little thinner. The separation is clearer and the vocal breath is more pronounced.
The SH-8’s treble has a certain maturity and is clearer and more resolving than the SH-8’s. Checking how this affected the timbre of the violin, we can say that it has become more emotional, but at the same time, having a lower volume, it seems hollow in some areas.
Loxjie A30
$189.99
Specifications
Although it would seem to be the perfect stacked combo with the Loxjie D30 DAC, the A30 already has a built-in D/A converter, albeit with lower performance, making it quite versatile.
For a wide range of enthusiasts, it can be used with headphones using its single-ended 100mW output, or with passive speakers equipped with an Infineon MA12070 Class-D chip delivering up to 80W per channel.
It has a rich list of digital inputs, including USB, optical and even Bluetooth. However, analog inputs are limited to single-ended RCA jacks and a 6.3mm headphone jack output.
Design
Compared to the HO100, the A30 is slightly lower and deeper, but has the same width. It has the same rugged design, but hides the screws at the bottom rather than at the back where the inputs/outputs are located.
By the way, the number of inputs and outputs located behind the device may seem quite cramped, but this is understandable since the A30 has both digital and analogue inputs, as well as speaker and subwoofer outputs.
At the front, we see a full-color IPS panel that displays the A30’s available controls, separating it from the HO100’s analog switches. Where I find the A30 to fall short is in its use of a short volume control, as opposed to the more pronounced control on the SMSL design.
Performance
While some audiophiles swear that neutrality is absolute and should not be touched, not everyone subscribes to this notion. This is where the A30 comes in, adding a fair amount of color to its amplifier section.
Compared to the HO100, the A30’s midbass may seem more lifted and weighty, but at the same time not too defined in texture. But the sub-bass on the drums lacks closure in the room, canceling out the expected boom.
Vocals sound clear and in line with the rest of the instruments. While micro-detail is not the A30’s strong suit, listening to acoustic guitars and pianos shifts the mood towards sweetness and appeal.
High frequencies do not have sufficient sound.
High frequencies are less clear and dark, but in some cases they can become energetic and even louder. Horns and violins are much more isolated and easier to distinguish on the HO100.
Specifications
Single-sided in design, the L30 still boasts that it features the same nested feedback composite amplifier (NFCA) module found in higher-end amplifiers from Topping, such as the A90. This is followed by a remarkable but slightly higher THD+N, measured at just 0.00007%.
Appreciating its IEM fan base, the amp also comes with three gain settings starting at -9.9dB, which can go up to 0dB and 9.5dB for less sensitive devices.
Design
The similarities between the two devices start with the aluminum frame with a reflective black panel on the front with clean cutouts for the toggle switches, headphone outputs and volume wheel.
This makes the usability between the two devices quite close and straightforward, with the only additional preamp feature available in the Topping implementation.
If you remove the branding, the L30 could be mistaken for a miniature HO100, which has similar depth but is thinner. Topping has gotten a little more creative, though, and offers its amp in four different colors, from stealth black to bright red.
Performance
Coming from a close competitor that similarly idealizes amplifier transparency, the Topping L30 is not to be taken lightly and is priced close to the HO100.
More straightforward in presentation, the L30’s neutral but slightly booming bass section has significantly less body and slam compared to the deeper, more pronounced boom of the HO100. When both amps tried to extract detail in more intense songs, the Topping’s low frequencies seemed more subdued.
The frankness I found in the vocal area of the HO100 can be applied to the L30 as well as their tonality. Guitars sound thinner and more plucked, and less reverb takes away from their stage presence.
The wind instruments sound louder, giving the impression that the HO100 is more refined in the top region. While the texture is crispier, it lacks the same amount of air and the cymbals are dull, contributing to the L30’s smaller stage.
Conclusion
Providing a satisfying level of transparency and refreshingly not too bright, the HO100 is a clean desktop amplifier that is well worth its price when paired with the right equipment.
With an appropriate level of transparency and refreshingly not too bright, the HO100 is a clean desktop amp.
With only a lack of micro parts and a cluttered low-end as its two main drawbacks, it’s easy to say that for a budget under $200, this new amp designed by SMSL is a step in the right direction.
And its low noise floor and three gain modes make it great for everyday use, keeping those interested in a versatile piece of equipment for their growing collection of over-ear headphones and in-ear monitors happy.
Price: $149
