Great entry level balanced headphone stack
Pros: + Transparent yet musical sound signature
+ Quite natural timbre
+ Great technicalities for the price
+ Dead silent
+ Fully balanced design
+ The DO100 can be used as balanced preamplifier
+ Powerful headphone amplifier
+ Internal power supply
+ Full size XLR plugs
+ Excellent build quality
+ DO100 comes with a remote control
+ Compact sized
Cons: – Not the most refined or resolving
– Slight traces of digital glare
– No MQA decoding
– No fixed line output for the D0100
– The HO100 lacks preamplifier outputs
The review samples were kindly provided by Aoshida Audio free of charge in exchange for my honest and subjective evaluation.
I haven’t received monetary or any other kind of compensation and I don’t use affiliate links.
The prices are $239 for the DO100 and $149 for the HO100.
You can buy them from Aoshida Audio here HO100 and here DO100.
Well, SMSL needs no introduction, founded in 2009 are specialized in the audio DAC, stereo headphone amplifier and power amplifiers with a very competitive prices.
They pay close attention to user feedback in order to continue improving on their products.
Aoshida-audio is one of leading Platforms which specializes in providing Audio Products, such as: Amplifier, Decoder, Player, Headphone,Cable and Accessories with high quality etc.
All products sold are original and covered by 50-day returns.
They are also part of the World Wide Hearing organization so a portion of every headphone sale goes toward helping a child hear.
SMSL and Aoshida Audio
SMSL DO/HO/AO series is a collaboration between SMSL and Aoshida Audio to build quality products with high value to performance ratio and specifications set by Aoshida Audio as they were collected by extensive user feedback.
The series was inaugurated with the DO200 DAC (review) the HO200 headphone amplifier (review) and the AO200 integrated speaker amplifier (review).
The series now continues with the more affordable AO100, DO100 and HO100.
SMSL – DO100
The DO100 is a high resolution audio DAC with a compact size suitable for desktop use in the most cramped spaces.
Measuring 150x128x39mm is just slightly larger than the SU-6 and considerably more compact than the DO200.
Despite the compact size, SMSL was still able to squeeze two pieces of the ESS ES9038Q2M chip, in a balanced configuration with regular XLR analogue outputs, pretty impressive for such a mini sized device.
The digital receiver is a 2nd generation XMOS solution that supports DoP256 and native DSD512 and PCM up to 32bit/768kHz.
A separate audio clock processing circuit is used to greatly reduce the jitter.
The user can choose between the seven available low pass filters to tailor the sound to his liking.
All input ports (except Bluetooth) support DSD transmission, coaxial and optical supports DoP64.
Four high-end dual op amp OPA1612 and a large number of audio grade components are used in the digital and analog sections.
What is great about SMSL is that they don’t use external power adapters even in their most compact devices.
The DO100 is not an exception since a built-in, discrete component, switching power supply is to be found featuring multiple low-noise power supplies for the analog circuits.
Wireless Bluetooth is also included through a Qualcomm latest chip that supports LDAC 24bit/96kHz, aptX, aptX HD, SBC and AAC.
Digital inputs include USB OTG type-C, coaxial and optical while stereo analogue signal is delivered through XLR balanced and RCA unbalanced outputs.
Both line outputs are variable so the DO100 can be used as a preamplifier to drive active monitors.
Unfortunately you can’t configure the line outputs as fixed and you have to use the maximum volume for a full scale level output.
The DO100 features a small, white LCD display which displays sampling rate and other useful information.
A multifunction aluminium knob is located at the right side and is used to control the volume and navigate through the menus.
Of course there is also a full-function remote control.
The unit comes ready to boot as it includes a Bluetooth antenna, a USB cable and an AC power cable.
SMSL – HO100
The HO100 is the headphone amplifier that stacks together with the DO100 to make for an affordable fully balanced headphone setup.
It has the exact same size and appearance as the DO100 so you can put the one on top of the other to save some space.
The HO100 is slightly more expensive than the budget friendly SH-6 ($120) but in exchange it adds a fully balanced design from input to output.
The amplifier features the SMSL patented technology that is named Ultra-low distortion precision feedback circuit with a distortion as low as 0.00006%.
A high precision low temperature drift resistance technology is used so the performance is not affected by temperature fluctuations.
High quality relays are used for a popless sound design and additionally the amplifier has comprehensive protection such as overvoltage and thermal protection.
The unit has a built-in, discrete component, switching power supply with multiple low-noise power supplies for all the critical parts of the circuit.
The amplifier is very powerful, it can do 3WPC into 16Ω and 1.5WPC into 32Ω from the balanced output with an output impedance near zero.
There are three gain settings high , middle and low, that can be selected from a toggle switch to meet the needs of different headphones.
The interface is pretty simple, you get full sized balanced XLR and single ended RCA inputs at the back but no preamplifier outputs.
The front face sports two headphone outputs, one balanced 4.4mm and one unbalanced 6.35mm.
A 3.5mm adapter is not included.
One switch toggles the input between XLR and RCA, the other is for gain selection and another is for powering ON and OFF.
An aluminum knob is for adjusting the volume, the potentiometer has a smooth and even rotation.
A slight channel imbalance can be heard in the lowest setting of the volume.
Build quality and appearance
The appearance is neat and minimalist, simple yet very stylish and modern looking.
Both units have a matte black finish and their chassis is made from thick CNC machined aluminium with a luxurious glass panel at the front face.
Both units might be affordable but they don’t feel cheap, they have top notch craftsmanship and great looks reminiscent of more expensive products.
Most of the listening was done with both units combined together as a stack but I have also hooked the DO100 to the HO200 and HO100 to the DO200 in order to check individual performance.
The units were burned for about 100 hours before listening tests.
I have mostly used headphones of the same price tag such as Sennheiser HD660S and HiFiMan Sundara but also included in the mix the Focal Clear Mg, Elex and a couple of IEMs to check the noise floor.
Speaking of noise floor, the system is simply dead silent with the blackest background you can possibly imagine making it the perfect companion for sensitive earphones.
The overall sound signature is balanced and linear with great transparency and tonal accuracy.
Fortunately this is not the bright, over – sharpened sound that is usually associated with budget Chi-Fi products of previous generations.
The sound is just a touch forward but not aggressive nor clinical or boring and in no way harsh or fatiguing.
Regular readers will probably know that I am quite fond of the ES9038Q2M because when properly implemented, it can sound enjoyable and realistic without sacrificing too much in technicalities compared to the grand ES9038PRO.
And such is the case here as the DO100 is musical sounding while maintaining the famous ESS transparency and precision.
The DAC stays true to the source material without any coloring from its part while the HO100 handles the amplification duties without tonal shifts.
The amplifier retains the same levels of transparency and linearity while it does a good job by adding the thrust and dynamics that are necessary for the sound to become realistic.
The experience can be as enjoyable and engaging as your headphones can be, this is the kind of audio gear that is not intervening so the transducers are the ones who will sculpt the final audio shape.
This is not a set recommended for manipulating the sound color in order to compensate for possible headphone deficiencies so make sure that you are going to use your favorite ones.
The texture is not too dry nor too lush while harmonics are presented with adequate saturation and intensity.
Timbre is satisfyingly natural, the stack doesn’t sound fake or artificial while digital glare is kept under control, you can only hear a minor edginess and metallic hue in the upper parts of the spectrum.
Technicalities are very good for such a modestly priced set, there is plenty of extension but while detail retrieval is absolutely stellar there is a lack in overall refinement and resolution.
On more practical stuff, bass is controlled, tight and layered with good dynamic range.
The stack is fast, agile with a pacing that stays steady even when things start to become really busy.
Frequency cohesion is excellent, all parts sound blended but at the same time each one stays clearly distinguishable by its unique articulation.
Soundstage is remarkably extended and holographic, especially when utilizing the fully balanced signal path.
Instrumental separation is clear, positioning accuracy is satisfying and so is the ability of the system in communicating the ambience of the recording venue.
As a whole, the SMSL stack proved an excellent performer, easily adaptable to all kinds of music from electronic to classical.
With the Focal Clear Mg, listening to this new complete recording of all Beethoven’s piano concertos was an immersive experience.
As good as they sound as a stack, both components can perfectly stand on their own without the slightest giveaway in sonic performance.
The DO100 is an excellent entry level DAC with a musical and precise sound reproduction that can also drive powered monitors.
And the HO100 is a great balanced headphone amplifier with plenty of power, excellent transparency and great dynamic range, missing only the preamplifier outputs.
Both are very competitively priced and can be used as single units to complement or upgrade an already existing system.
Nothing much to add here than the usual lack of ultimate fidelity especially in the treble.
The Bluetooth implementation is really good and the ease of use can make up for the slight loss of sound quality.
Given that, the DO100 is better from the wired inputs and should be used as such when possible.
Compared to the rest of the family
Things are pretty simple, pricing honesty and scaling are the plain characteristics of the family.
The SU-6/SH-6 is a great entry level stack for all people who would like to experience good sound for less money.
Then you spend a little more for the DO100/HO100 stack and you get a little more of everything but only if you have balanced headphones, otherwise don’t bother.
You gain in transparency, resolution, extension, dynamics, instrumental separation and positioning, holography and overall technicalities with the same kind of sound signature.
And if you can afford it, then you aim for the DO200/HO200 system which sports dual ES9068AS chips that can do full MQA decoding and the amplifier is much more powerful plus it has preamplifier outputs.
Sound-wise, you gain even more of everything reaching for a higher level of sound quality given that you own an equally good set of headphones.
A very honest price to performance ratio and scaling, you get exactly what you paid for, so kudos to SMSL for respecting your hard earned cash.
In the end
The SMSL DO100 and HO100 both combined or as separate units, are entry level balanced audio devices with great sound and excellent price to performance ratio.
They are well built and despite the compact size, they come with full sized XLR plugs.
The actual value is unbeatable so if you are looking to step into a fully balanced headphone system then look no further, the SMSL stack has you covered both in sound and build quality without breaking the bank.
Copyright – Petros Laskis 2022.