I usually start my reviews by introducing the manufacturer of the product I’m currently reviewing, but come on, you know SMSL. One of the leading manufacturers of DACs and amplifiers for years now, offering an extraordinary value and one of the best measuring devices in the world of audio.
Let’s get to the hero of today’s review, the HO100. This is a pretty basic headphone amplifier capable of providing up to 1.5W into 32 ohms. It’s balanced (the balanced output is a 4.4mm jack), it has three different gain settings and that’s about it.
We’re pretty much used to SMSL stuff sounding as neutral as it gets. They’re just pushing the prices of their devices lower and lower, delivering better performance. While the competition in the +/- $150 price market is pretty crowded, SMSL is known of doing good things that are priced well. Let’s see how it is this time.
The unboxing experience of the HO100 is pretty straightforward. It comes in a minimalistic white box with a clean graphic of the amplifier on the top lid. Inside you’ll find the HO100 amplifier and a power chord, that’s all. What else do you need?
The quality of the packaging is definitely enough. It looks clean and is secure, so the HO100 will come to you unharmed (it’s not a challenge FedEx and DHL!).
Design, Build and I/O
The HO100 is made of CNC machined aluminum and it feels pretty solid. It’s a rather small amplifier, the same size and shape as the DO100 DACs, but it feels substantial and dense in hand. The size feels just about perfect for any desk scenario.
The actual build quality is pretty good, there are no sharp edges, it stays in place thanks to the rubber feet, and looks just great paired with the DO100 DAC. It has three different switches to turn the device on/off, change between RCA and XLR inputs and choose the gain (there’s low, medium and high, a great feature in an amplifier in this price bracket).
From the design point of view, this is yet another SMSL headphone amplifier. It’s black, minimalistic, and just an aesthetically pleasing device. Nothing to write a book about, but certainly nothing to criticize. I somewhat miss the times when different amplifiers really looked different, but I actually understand this kind of approach. This design has been here for years, it’s safe and just good.
Let’s talk about the I/O. The HO100 has an RCA input, and XLR input…and that’s all. They cannot work simultaneously, you can only choose RCA or XLR. As for the output, you’ve got a single 4.4mm balanced headphone out and a single 6.3mm. This is the best combination for a modern, small headphone amplifier. The 4.4mm balanced output got to the point where it’s a golden standard (bye bye 2.5mm, at last), and the 6.3mm output will work well with most affordable over-ears.
Lastly, the HO100 has a built-in ultra-low-noise power supply, so say goodbye to chunky power supplies laying around on the floor. All you need is just a simple power cord and you’re ready to go. To see a quality power supply in a device this small, with all its features is pretty impressive, to say the least.
Okay, now into some tech. I’m going to put some numbers here for all of you crazy people that like to read it. Just kidding, this is pretty essential for a good performance of a headphone amp nowadays.
So, first of all, the HO100 offers a near 0 ohm headphone output, with distortion going as low as 0.00006%, this is just ridiculous. Next up, the output noise of the power supply is as low as 1.3uV.
The HO100 outputs up to 1.5W into 32 ohm. This is not really impressive as for the year 2022. I know SMSL has aimed more at ultra-low distortion, and to be honest, 1.5W is pretty enough for 95% of people buying in this price range. However, if you think that the HO100 will run your demanding headphones like the HEDDphone, HD8XX, D8000 Pro or the Hifiman Susvara…think again. However, who on earth would pair a $149 amplifier with such headphones? Well, I’m partially this kind of person, I want to see how hard I can push that kind of device, and the truth is…not too hard.
The gain switch is a very nice addition for an amplifier in this price range. The low level is rated as -9.5dB, middle sits at 0dB, and the high gain is 15.5dB. Thanks to that, you’ve got yourself an amplifier that can be highly flexible, depending on your headphones of choice. Got some ultra-efficient IEMs at your hand? go for the low gain and you’re pretty much set. Need more juice? You can always toggle the high gain and push some power. This is a great flexibility, and I like flexibility.
Now onto the sound quality of the HO100. This is a $149 headphone amplifier, so it’s essential to know if you’re getting good quality audio for your money. The answer is simple – yes, you are.
Just like the DO100, I’ll be doing this review in a different way than usual. Instead of focusing on every frequency one by one, I’ll try to imagine some use case scenarios and see if the HO100 is a good choice for different kinds of people.
So, let’s begin with audio rookies. You’re getting started with this whole audio stuff, got yourself a pair of good headphones like the 6XX, HE400se, etc. Now it’s time to upgrade the rest of your system. The DO100 + HO100 combo is going to cost you slightly less than $400. This is by no means dirt cheap, but it’s not expensive either.
If you’re just starting, you have to justify spending 400 bucks on a DAC+AMP combo, it has to improve the quality of your sound. This is the best-case scenario for these products. Both DO100 and HO100 will give you an incredibly clean and high-fidelity audio with basically no sacrifices. You don’t need crazy high power from your amplifier, your journey is months or even years before getting these ultra-demanding, multi-thousands dollars headphones, so you’re pretty much set. WIth the DO100 however, you’re not getting MQA. If you use Tidal on a daily basis, this might be slightly concerning for you. What I would recommend to you is to read the entire MQA drama first, then try MQA for yourself and decide whether you like or need it.
Okay, so what will the HO100 actually give you? Clean, super clean power. Not a lot of power, but you don’t really need it. Aiming for clean audio at the beginning is pretty essential, as it will allow you to “learn” what good quality audio is. Back in the days when I was starting my audio journey, I had a lot of friends with systems that were $1000 that never actually experienced good quality sound. They bought some weird boutique devices that were well-made and sexy, but they sounded distorted and their tonality was far from accurate. Lucky you, you’ve got a much easier job. You’re grabbing a DO100+HO100 combo and the sound you’ll be getting is as neutral and as clean as you’re even capable of hearing at this point.
Let’s hop into a different situation. You’re a tube guy, you like big, glowing tubes (well, I can’t judge you, I’ve been there, have done that, and I still like tubes). However, a tube amplifier is not ideal, it often sweetens the sound by a lot, they run hot, they’re often big and heavy, taking a lot of space on your desk…and you cannot stack them, a tube amp has to sit on the top and you’re never putting anything on top of it…never.
So, you’re starting to think – damn, I spend so much time at my desk every single day, how nice it would have been to have a small amplifier that I can stack, that sounds neutral and clean and it’ll handle both sensitive IEMs and over-ear headphones. Guess what, the HO100 is a great answer to that situation. If you have a DAC that can output but XLR and RCA, you can have the HO100 AND your tube amp plugged in at all times and just switch between them when it’s convenient. Will it make your life easier and more enjoyable? Probably yes.
Last case scenario. You want to review audio stuff, or you’re already doing it, and you’re not wandering into the high-end regions just yet. You definitely need a hyper-neutral, super-clean sounding amplifier so you’ll have an easier job actually reviewing headphones, DACs, and cables? The HO100 can give you all of that. It’s pretty hard to review headphones on a highly colorful sounding amplifier, so the HO100 could be just perfect for your “entry-level” benchmark tool.
Okay, okay Paweł, you used the words “clean”, and “neutral” so many times and I still don’t know how does the HO100 sound? Well, it kinda…doesn’t sound like anything. This is so pure and flat that it sounds like the rest of your system, but more powerful, which for some is the ultimate kind of performance of an amplifier. The HO100 won’t make your bass more powerful, vocals more real and soundstage any bigger than it already is. This device will make sure that the signal of the DAC is strong enough for your headphones to reproduce it 100% correctly, and that’s about it.
You might read it and think to yourself – well, that’s underwhelming. But in my opinion, this is actually the opposite. This is an entry-level device, and it doesn’t sound like anything. It just offers a very high-quality, clean (again), and fast performance, and it is up to you if you’ll be able to appreciate it. Take note though – if you’ve got some exotic DAC or the headphones that are not really good…the HO100 will not make them sound better, definitely not. Actually, they can end up sounding even worse, because all the doubtful qualities of the previously mentioned elements will be multiplied with a higher signal. You’ve got that problem? Get the DO100, a Hifiman Edition XS and you’re set for months or even years of enjoying music. At the end of the day, you might never need to upgrade.
Pawel cut the crap and give us some ideas of what to pair the HO100 with! Okay, okay…fine.
1. SMSL DO100 + SMSL HO100 + Hifiman Edition XS
This is the ultimate neutral and flat-sounding system you can get at sub $1000. Every piece of equipment in this setup is just neutral and technically impressive. This setup will give you an uncolored sound that is filled with detail and resolution. I’ve said it once, and I will say it again – You’d have to pay thousands for this kind of performance a couple of years ago, and now it can be yours for under thousand bucks. What a time to be an audiophile.
2. SMSL DO100 + SMSL HO100 + Drop + Hifiman R7DX
Similar to the previous system, but now with a closed-back pair of headphones and even more affordable, actually quite a lot more.
The star of the show. While listening to the DO100 + HO100 stack I was pretty impressed, but when I tried this combo with my Fir Audio Xenon 6 CIEM ($3899) I was absolutely blown away. SMSL points out this “super clean” aspect of these devices, and they’re not lying. This combo has virtually no hiss, pitch-black background, and exceptional clarity. If I listened to this setup and you would tell me that I’m listening to the XENON6 out of a high-end DAP, I would have probably believed it.
4. A DAP + SMSL HO100 + Just about anything
Imagine that – you’re more of a portable audio guy, but you do listen to music in your home, or while at work sitting by the desk. Your DAP sounds great but it just lacks some juice for more demanding, over-ear headphones. You like the sound of the setup, but you’d just want more power? Just get the HO100, plug it between your DAP and your headphones of choice and you’re set. Now you’ve got that sound that you really like, but louder, more pronounced with better dynamics.
The SMSL HO100 is a definition of a high-quality headphone amplifier. It doesn’t have a “sound”, it’s strong enough for most headphones in the affordable price market, and it’s highly technical with fantastic cleanliness and detail. Add a three-level gain setting and a 4.4mm balanced output and you’ve got yourself a banger for just $149.
Gear used during this review for the sake of comparison and as an accompanying equipment:
- Headphones – Hifiman Susvara, Final D8000 Pro, Audeze LCD-X 2021, Hifiman HE1000se, Abyss Diana PHI, Drop + Sennheiser HD8XX, Crosszone CZ-1, HEDDphone, Meze Empyrean
- Sources– Topping D90se + A90, Ferrum OOR, EarMen Tradutto, Musician Pegasus, JDSLabs Atom DAC+/AMP+, Cayin N3Pro, Pro-Ject Debut Carbon PRO + iFi Zen Phono, xDuoo TA-26, XI Audio Broadway S, Musician Aquarius, Cayin HA-300, Cayin HA-6A, Fiio M17, Cayin N8 ii
Big thanks to Aoshida-Audio for providing the HO100 for this review. I wasn’t paid or asked to say anything good or bad about this product, all of the above is just my personal, unbiased opinion. Aoshida-Audio hasn’t seen this review before publishing it.
You can get your SMSL HO100 on Aoshida-Audio here.
Founder of Ear Fidelity. I’ve been into audio for many years, working in production, distribution, retail, and marketing throughout my career. Now trying to revolutionize the art of reviewing audio gear, but one thing will never change: Music is the most important.