SMSL AO100 Amplifier Review

Last month, I reviewed the SMSL HO100 and DO100 Headphone Amplifier and DAC units and enjoyed my time with the small headphone stack. This month, I was given an opportunity to check out the matching speaker amplifier, their all-new SMSL AO100. The amp sells for $129 and can be found on Aoshida Audio's web site at https://aoshida-audio.com/products/smsl-ao100 

This review unit was provided by Aoshida, as was the previous HO100 and DO100 units.

The HO100 shares the same all-black box look of the matching HO100 and DO100 units, and like the others, features a glossy glass front panel, with a volume knob on the right hand side and a digital display with white OLED on the left.

The rear of the unit has speaker taps, RCA input and output (for subwoofers or powered speakers), and a bluetooth 5 antenna. 

The amplifier is rated up to 70W at 4 Ohm, which is a bit of a wattage inflation, since most amps show their 8 Ohm wattage, so let's just assume its roughly 35W. This is still a sizeable amount of power for small satellite or desktop bookshelf speakers. The amp is powered by the German, Infineon MA12070 integrated Class-D amplifier chipset.

The unit also comes with a generic SMSL remote that can change several settings within the amplifier. These include cycling input from Line In and BT, changing volume, changing bass, mids and treble levels (basic EQ functionality) along with 4 or 5 preset EQs, Gain level (low or high), and surround sound effects (3 effects and off).  

I only briefly used the surround effects, but did not like them on my setup and my music. They just make things brighter to the point that I found them annoying, and decided to just leave all tone and surround controls to off. 

Sound Impressions

I have done quite a bit of downsizing in my stereo and home theater setups in the past 5 or so years, going down from large tower 2 channel setups, and 7.2 home theater rooms down to a pair of powered monitors, a 2.1 bookshelf/subwoofer setup, and a soundbar. This wasn't all by choice of course, but compromises were made. Luckily for this amplifier review, the downgrade to a 2 bookshelf and subwoofer living room setup is the perfect combination in terms of power requirements for this little amp.

My listening setup for this amplifier was a combination of BT and line-in from my iBasso DX240 amplifier, and output to a pair of Focal Bird speakers and Focal Air Subwoofer. This small compact set has a nice clean sound that leans a tad bright but surprisingly has good detail and imaging, though may not the best for the thick and heavy midrange affairs. 

I normally use this setup with a Pioneer X-HM86 streaming receiver setup, using that setup with Roon via Airplay, and various streaming services and of course, good ol' compact discs. This isn't exactly a well known setup, and with Pioneer making less and less stuff now, especially with their sell-off, I don't know how much use this comparison will be, but it is what I have now.

The Pioneer has always given me a sort of v-shaped sound signature, whether I use it with speakers or with headphones via its headphone amplifier. It's not quite neutral, and emphasis is on bass and treble, while still sounding decent, it's not always my preferred listening experience with certain pairings.

In contrast to this, I find that the AO100 is quite dead neutral. The bass levels drop quite a bit, and it is very significant enough, that I need to bump up the level on my Focal subwoofer slightly higher, although I did not put it to the same levels as what it sounds like with the Pioneer setup. This could just be an impedance mismatch perhaps, so once level, it sounds quite a bit better to my ears.

I threw on a gambit of jazz, country, indie and alternative rock through out several days of listening to this setup and I kept coming back with the same impressions. This thing just sounds neutral and actually surprisingly clean, and resolving. It brought out quite a bit more details than my Pioneer X-HM86, and depth and layering was quite a bit better. The Pioneer is also powered by a Class D integrated op-amp but I can't remember which one it is off the top of my head, for reference.

I was most impressed with how this combination sounded with my jazz collection. Joey Alexander's new record, "Origin", has a plentiful amount of instruments and sounds in the first couple tracks. "On the Horizon" came out clear, with nice sweet and distinct smattering of hi-hats and drums, all the while, Alexander's piano notes swirled around it, along with the reed instruments wailing around. 

To be honest, I was expecting a brightly-tilted sound that sounded dead. Instead, I actually am hearing a good amount of dynamic range, and good impact on bass notes, and clean and resolving notes. Transients are crisp and clear, and this makes me wonder how much I am limiting my Focal speakers setup with my current amplifier setup, wanting an all-in-one solution on the budget, with a display. Perhaps I am better off getting practically anything else, as this SMSL AO100 is what? $129? And its blowing my more expensive Pioneer amplifier out of the water, granted it's older, and it does more things....

Headphones?!

Next up, I put the amplifier to the ultimate test. How does it handle HEADPHONES?! Of course, how can a primarily portable audio site, not cover something ridiculous as playing headphones out of speaker terminals on the back of a power amplifier?

I have a speaker tap cable set-up that I made for my Hifiman Susvara when I was amp-rolling with a bunch of speaker amps and headphone amps and pulled that out of the garage to conduct some listening trials with that headphone and the Sennheiser HD580. 

Sennheiser HD580

I first used the HD580 and the very first thing I noticed was that amplifier noise was bleeding through on low-gain. Of course, this wasn't super surprising. Only crazy insensitive headphones like the Susvara would be able to neutralize such amp noise from a speaker amp anyway. 

The 580 sounded quite nice. Punchy bass, highly detailed mid-range and crisp highs. There wasn't anything that really stood out besides my first impression was this is perfect neutral. Dead neutral perhaps isn't the right term since I sometimes use dead as a sound of no dynamics, and this doesn't lack that, but dead-on neutral target it is.

Hifiman Susvara

If you know anything about the Susvara, outside of its exceptional sound, you'll hear about how incredibly hard it is to drive. It's one of the least sensitive headphones on the market, and many people use full-blown speaker power amps to output audio to these. 

In my case, I've gone through several amps and headphone amps and settled on the Bakoon AMP-13R which is both a speaker amp and a headphone amp, and shares the raw power of both into the headphone jack. 

So in this case, I compared it to the SMSL AO100 which is kind of laughable at first -- comparing to a several kilobucks headphone amplifier with a just over $100 unit, but hey, this actually wasn't that bad of an amp for the Susvara.

The AO100 via the Holo Spring 3 KTE DAC was able to output plenty of decibels to the Susvara to get my music loud. In listening to more Bill Laurance jazz music, I got punchy drum hits, and incisive piano keys with a decent low end and non-fatiguing sound. Perhaps this is the Spring 3's doing, but I was surprised that the overall balance was not steering towards bright and fatiguing properties. Instead, I was actually quite happy with the results, though it does not have the full bloominess and low end warmth and layering of the Bakoon. That said, this is doing a great job playing music.

Now, when I crank the volume up higher than my normal listening volumes -- say 70dB SPL, I do find the pairing to become very full-forward with some lacking of clarity and imaging goes down with directionality becoming just a blob and wall of sound than distinctness. That's fine since going above a certain volume threshold with headphones is not really my thing anyway.

Overall

The new SMSL AO100 is a nice little petite amplifier that can get the job done with small speakers. While I did not try it with full-ranged tower speakers or anything that demands a lot of wattage, I don't think it will be able to handle more than a bookshelf speakers with high sensitivity. That said, I was surprised by the clarity and resolution of these amp and that despite being dead-on neutral, that it didn't shy away from having some punch and good treble extension without being overly fatiguing.

It's a good priced amp with good features, bluetooth, and a nice remote. I must say, I'm impressed for this price point.

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