General Information

The THX AAA-888 Offers Extreme Clarity

The THX AAA lineup of amps are known for their power and clarity. Unlike many amplifiers, THX AAA amps use a feed-forward error correction topology that removes common distortion issues. To put it simply, the amp measures errors in an early part of the system and corrects them in a later part of the system.

The THX AAA-888 is the most sophisticated iteration of the lineup. Its distortion levels are seriously low. Signal-to-noise ratio is 137dB, meaning that you’d have to crank the amp up to 138dB before hearing any hiss. And unless you’re trying to permanently damage your eardrums, you’re probably not going to do that.

Desktop Friendly

Despite its massive output capabilities, the SH-9 is actually quite small. At 7.3” on its longest size, you should have no problem fitting it onto most desktops. And as we said, it’s designed to stack with the SU-9. The stacked pair are a modest three inches in height.

Product highlights

  • THXAAA-888 Headphone Amp with THX AAA Technology
  • 6W into 16Ω, 3W into 32Ω
  • Frequency response: 0.1-500,000Hz
  • SNR >137dB
  • THD <0.00006%
  • Ultra-compact design that’s perfect for desktops
  • Balanced stereo headphone output
  • Balanced stereo line input
  • HIgh precision resistors for temperature stability
  • Pop-less design with high-quality relays
  • 256-level relay volume control
  • Switchable gain control
  • 1.9” LCD display
  • Remote control
  • Inputs: 1 balanced, 1 unbalanced
  • Outputs: 1 balanced, 1 unbalanced
  • Output power
    • 6W x 2 (16Ω)
    • 3W x 2 (32Ω)
    • 440mW x 2 (300Ω)
    • 220mW x 2 (600Ω)
  • Output noise: 1.9uV, A-weighted
  • THD+N
    • -123dB, 0.00006% (A-weighted)
    • -117dB, 0.00013% (20-20kHz, 32Ω, -3dB)
  • THD: -125, 0.00006% (1kHz, 16Ω, -3dB)
  • Input impedance: 47kΩ
  • Output impedance: Near 0Ω
  • Gain: Low (+0dB), High (+10dB)
  • Power supply voltage/frequency: AC100-240V, 50-60Hz
  • Power consumption(EN60065): 24W
  • Power consumption in standby mode: <0.1W
  • Size: 7.38 x 6 x 1.5” (187.5 x 154 x 40mm)
  • Packing size: 11.1 x 9.1 x 3.1” (282 x 232 x 79mm)
  • Weight: 1.7lbs (790g)

What’s included

  • SMSL SH-9 THX AAA-888 Balanced Headphone Amp
  • Remote Control

Latest reviews


Best amp under 300$ imo
Pros: Build
Cons: Not truly balanced?
Smsl sh9

Digital volume contro
super clean and detailed. Matches very well with different types of DACs. Doesn't sound like other thx amps even with the same thx chip.
Good power output.
Pairs well with all headphones and iems
Bass is fast deep and hard then completely disappears in an instant
Mids are detailed with texture and no hint of cool or coldness to them
Treble is clear and exactly as it should be ,very clean
Excellent soundstage

THX 888 chip inside, same as the SMSL SP200 but it sounds different and much better!

Not truly balanced.

• Frequency Response: 0.1 Hz – 500,000 Hz
• SNR: >137 dB
• THD: < 0.00006%
• Balanced IO
• 256-level relay volume control
• Switchable gain with pop-less design
• Output Power: 6W x 2 (16Ω), 3W x 2 (32Ω), 440mW x 2 (300Ω), 220mW x 2 (600Ω)
• Dimensions: 187.5 x 154 x 40mm

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Reviewer at Ear Fidelity
Pros: Powerful
Great value
Minimal looks
Build quality
Very universal sounding
It's just a fantastic amp overall
Cons: Cant find any for the price, I'm sorry.

SMSL SH-9 is a balanced headphone amplifier based on the THX888 chip. It provides 3W through the balanced output and costs 289$.

Sound quality for the price
Rating: 10 out of 10.

Build quality
Rating: 9.5 out of 10.

Rating: 10 out of 10.


THX – nothing interesting? Not this time.

You may think, oh, that’s another amp based on the THX chip, nothing interesting. Well, I won’t lie, my first feeling was the same. All of them are similar, but this one is different. SMSL has changed a lot in their playstyle by the time, from one of the most “digital” sounding devices to one of the strongest participants in the Chi-Fi race.

My opinion about the THX amps has changed after the first listening session, and it changed a lot. Why? You’ll know that after reading the following paragraphs.

Packaging & Build Quality​

Only inputs, nothing more.

The SMSL SH-9 was made to be a pair for the SMSL SU-9, so it looks almost the same. The only differences are the headphone outputs on the front and a small THX logo on the top. I’m delicately sad because there are only 4pin XLR and 6,35mm jack outputs on the front. I wish there had been a 4,4mm balanced output implemented as well.
There are only two analog inputs on the rear— one pair of RCA and one pair of XLR.

The overall build quality is excellent. It’s a really solid piece of metal.
The screen has the same colors as the one in SU-9, but it has a more expansive range of brightness settings. 2/6 is the same as 1/6 in SU-9, and the 5/6 is equal to 6/6 in SU-9.
What else can we change using the menu? Not much, but there are all necessary things. To be honest, it has the same functionalities as the switches in the SP200. You can choose the input, gain, the volume mode, and set the brightness.

Almost the same.

The potentiometer has an excellent click, and it’s absolutely correct. Thanks to being digital, there’s no channel imbalance, which is ideal to use with low impedance IEMs or to listen quietly.
Inside the box, you’ll find the same set that comes with SU-9, so only the amp itself, power cord, remote, and some paperology. The producer doesn’t provide any interconnects, even basic RCA. On the other side, if you already have some cables, you don’t pay extra for the ones in the box.
The SH-9 gets really warm during usage with low-impedance planars on high gain, so provide the SH-9 a decent airflow.


THX AAA technology – what is that? That’s a shortcut for “Achromatic Audio Amplifier,” which means the THX involved that standard for amps to be, well, achromatic, so they don’t colorize anything. That makes all the THX AAA amps have the lowest possible THD distortions, set at 0.00006% this time. Keep in mind that the SH-9 isn’t truly balanced. The final power is the same using both outputs, and the balanced input is here just to give you more options.
The chip inside, the THX 888, is the same as the one in SMSL SP200, but the final result is different.
Besides that, it’s the amp that goes great in all possible measures. But how does it sound for real?


Beautiful and simple stack.

Well, that’s a challenging part to describe because the SH-9 provides a really clear and transparent sound without implying much to the sound. As I mentioned at the beginning, I wasn’t genuinely fascinated by the SH-9 at the beginning, because all of the THX amplifiers I’ve heard sounds similar. Dry, dull, correct like Netflix’s tv series. The only similarity of SH-9 is being unbelievably exact but absolutely not dry or flat. And I like that a lot. It provides a lot of fun in every point of this word’s meaning.
If I’d have to say which frequency is the most prominent in terms of sound signature, I would say it is like the podium, where all competitors win the competition.
If you’d like to use the SH-9 with IEMs – feel free to do it unless you have some truly sensitive IEMs, like CFA Andromeda. Using all the earphones I have, I can hear only a delicate background noise that isn’t disturbing for me. I can’t hear that when the music is playing.

The queen and the king.

The bass is a speedy and punchy beast. It strikes from nowhere to disappear in the blink of an eye. It’s perfectly separated from the other frequencies, always keeps its place in the row, which has the same importance as the rest. That’s matched with excellent power in the sound, with nice subbass addition. As you can expect after the insanely low THD+N measurements, it provides a lot of texture that’s not exhausting because it doesn’t bring any dryness. It matches all headphones I’ve tried, starting with the cheap Moondrop SSP, ending with the Audeze LCD-3. Every time it wasn’t overwhelming or indisposed, always perfect and lovely. With that bass, my guilty pleasure is listening to Russian techno, also known as hardbass. I’m afraid the LCD-3 that I use for that will someday say hello to me with beautiful “сука.”

As expected, the midrange also provides a nice texture, but it’s delicately softer than the texture in the bass. As the main difference between the SMSL SP200 or even the FiiO M11 Pro, the SH-9 has some life in it! It isn’t cold, but it easily lets me feel the music, start dancing, singing, and so on. The theme or the headphones I choose doesn’t matter. Whenever I’m listening to SH-9, I enjoy the music and being enamored by all the insanely accurate details. Apart from those in the higher part of midrange, it sometimes lacks vitality, but really rarely. Besides that, I can’t say a bad word about the mids.
Oh, and one exciting thing – with high gain, the vocals come closer to the listener. That’s the most visible using Audeze LCD-3, but it happens with all cans I’ve tried.

It doesn’t affect the sound signature of a headphone of choice in any way.

The treble is somewhat boring to describe but not to listen to. It’s just absolutely clear, clean, and exact. If the track has correct mastering, and your cans don’t tend to sibilance, you won’t face any. Using AKG K702, sometimes I can hear some sibilances, but only with poor-produced tracks. Using Craft Ears Four, Campfire Vega 2020, or the Audeze LCD-3 – not a single sibilance. Only incredible details and a lot of air. I love how the drum plates sound. When they play, I can even see and feel how they’re shaking. I’m in love with classical music for the last few days, so one quick example with “The Pianist” soundtrack. It sounds wonderful. It provides a feeling of a true piano, no matter what headphones I try. It’s intimate and powerful at the same time.
The rest stays for the headphones’ side. The SH-9 will show you what they truly can.

The soundstage is excellent, but it delicately misses the height. From all the directions, I can hear everything with the sounds that go around my head to swirl into it at the end. And that’s nice. The SMSL SH-9 doesn’t ruin any soundstage, doesn’t provide extra magic and fading, and doesn’t take it away. Only the style that headphones offer, with a delicately lowered ceiling. So, whatever you like in your cans stays here. Do you prefer more exact pinpoints? You got it. Or maybe you want to have more fading and going all-around style of your headphones? Don’t worry, you’ll have that.
It was as useful as the LittleDot MKIV I reviewed a while ago during the gaming sessions. It means the SH-9 is now my best friend for gaming. The directions are way more exact than my friends’ info.

Low impedance IEM? No problem.


As I mentioned above, the SH-9 matches with every headphone perfectly. So, only if there’s enough power for you, and there should be, you can feel safe putting the SH-9 in the shopping cart. Of course, if you’re looking for a transparent AMP that shows everything that cans want to show.


LittleDot MKIV
is a tube amp, so obviously, those two sound completely different. LittleDot provides a smoother, more analog sound with delicately worse details at the ends of the frequency range but a better height of the soundstage. It is also more natural and delicately calms the headphones. After that, the SH-9 is way smaller, so it’s a better choice if you have limited space.

Topping DX7 Pro (vs. SH-9 paired with SU-9) has a colder sound, slightly worse microdetails in the midrange, and a soundstage placed way closer. The height is similar, when the width closes faster, it has the same exaction level.
It also provides less power and has a more technical playstyle, which delicately increases the overall sharpness. But it is 100$ less, and you don’t need any external cables. I love both the DX7 Pro and SMSL combo, but I would rather choose the SU-9 and SH-9.


Simple yet elegant. Ear Fidelity approved.

The SMSL SH-9 is a beautiful AMP that has no weak points in the sound. A lot of details, being transparent without cutting off anything, letting the headphones be how they are. So, we have ab excellent build quality, a lot of power, and it pairs with all headphones I have perfectly. For me, it sounds like an absolute amp. If you watched 3rd part of Star Wars, you probably know the verse “Only a Sith deals in absolutes”, and that amplifier will deduce you from the mistake.

Absolutely recommended.

Disclaimer: SMSL SH-9 was sent to us in exchange for an honest review by Apos Audio – Thank you!
This review is my unbiased opinion, and it wasn’t influenced by anybody.

You can get your SMSL SH-9 here.​

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1000+ Head-Fier
Pros: Sound is super clean and detailed. Scales really well with different DACs. Doesn't sound super cold and clinical. Decent power output.
Cons: Not truly balanced. Missing a few EQ features the old SH-8 had. Gets toasty after a bit. Still a bit warm sounding amp compared to other good measuring amps.

What I always felt made the now old SH-8 special was that at the time you could get a nice balanced amp for only $190. It was on the fairly neutral and somewhat boring sounding amp on its default setting but it has an on board EQ so you could fine tune it a little or even use their SDB setting which gave the amp SMSL’s own flavor of sound. Power output was only a little under 800mW when using balanced so It lacked some power as well. The SH-8 was mostly my main amp for the last two years and I very much enjoyed using it daily. When I saw the new SH-9 amp announced I was really interested to see what the upgrade could bring to the table over the SH-8.

Thanks to ShenzhenAudio for hooking me up with a review unit. While I always appreciate stuff being sent in to test and review, It never affects the ratings of my reviews.

More info on the SU-9 plus the purchase link will be below!

Gear used

IPhone 12 Pro via RCA, SMSL SU-8/9, iFi NEO, Ikko OH10, ADV M5-5D, LCD2C and Dan Clark Audio Aeon flow “RT” closed.

Looks and Feel
Much like the SU-9 I recently reviewed, I really like the looks over the now old SH-8. The included lcd screen and included remote makes for a nice upgrade over the SH-8. The back of the unit is fairly simple with a XLR in or RCA in. I was slightly bummed the SH-9 has no outputs at all. I felt they could have had pre outs for at least RCA.

Accessories and unboxing
I had the exact same unboxing experience as the SU-9 I just reviewed. There is a remote included with the amp which is awesome. The older SH-8 didn’t include a remote which was always a bummer.

While I really appreciate the new UI over the old SH-8, it’s a little easier to simply use the remote to change things. I don’t mind that no physical switches were included on the device. It’s fairly uncommon for me to switch gains constantly and it’s easy enough to swap between the inputs or gains using just the volume knob if you're not willing to fetch the remote.

Volume knob
I really like the little relay system in place for volume control. This, from what I read, is a little rare and mostly in more expensive amps. There are two settings for the volume relay control. The default setting(off) means any single adjustment in the volume knob will activate the relay which results in a click noise. The second option(on) means you can adjust to a volume number you may know you like and then the relay will activate once and adjust the volume to your intended selection. I leave the setting to change with each volume step since I don’t like having to wait for a relay to activate and lower or raise the volume I want. It’s claimed to save the relay lifespan but I rather have instant volume changes. Plus I I've read these kinds of relays have super long lifespans.

These will be my impressions overall with the SH-9’s sound signature when used with all the iems/headphones and few DACs I threw at it.

Lows take an accuracy approach for the most part depending on the DAC. There is good quality and decent thumps in the low end. This isn’t a clinical low end and things still sound fairly dynamic and musical still. That being said, if you want to add bass to lean sounded headphones, this won’t really help much. Since the onboard EQ that the SH-8 had is missing, you will have to software EQ if you wanna adjust the general sound to a boosted low end if that’s what you want. Some DACs like the now old SU-8 sound a bit more low end boosted due to how warm sounding the SU-8 is.

Mids come through with extreme accuracy and on the three main DACs I used, they all tended to have a little recessed feeling with the vocals. This makes for a lower volume of the voices while instruments sound a little louder and closer to your ears. I personally like it this way so for me it was fantastic but for others it may differ.

The highs come through very detailed depending on the DAC used. This is also a very accurate sounding amp for the highs and things can come through either neutral or bright. On something like the SU-8 or iFi NEO, Things can sound warm and relaxed up top. When paired with something like the SU-9 you start to creep into a brighter top end. This of course will depend on what you have plugged into the SH-9 headphone wise. The SH-9 doesn't suffer from sounding super bright however like some prior well measuring amps do.

The common thing I noticed here was that the stage feels a little average on width no matter what DAC I use. The depth was what changed the most depending on the DAC it was plugged into. While it won’t go crazy deep, it still gave a nice deep feeling on both the SU-9 and iFi NEO. Imaging was great across all sources but I believe this is a little more dependent on the DAC than it is on the amp.

Single ended output/Balanced outputs
I decided to make this one section since one thing missing on the SH-9 is a truly balanced amp design. Sure, there are balanced XLR inputs on the back and a 4pin XLR jack on the front, yet it’s still a single ended layout inside much like their SP200. I have mixed feelings on this since the old SH-8 is a truly balanced design and SMSL decided to make their SP400 which costs about twice the amount for a truly balanced design. That being said, both the single ended and balanced jacks produce zero noise, to my ears, on my sensitive iems. I was fairly impressed by this. There are also 3 watts on tap for both jacks so I really like that it will power my current gear and most of the headphones I would plan to buy down the road. Very impressed with the power output for the price.

XLR vs RCA inputs
Well since the SH-9 isn’t balanced, one might be wondering why anyone would use anything other than the RCA inputs for the SH-9. While using XLR isn’t necessary, one advantage is that most DACs output higher voltage via their XLR outputs. So when something like the SU-8/9 are going XLR into the SH-9 you get a much louder volume vs RCA. While running RCA from the SU-9 had a volume of 32/99 for my M5-5D, switching to the XLR input made it so that 22/99 was the same volume that I liked. Something to think about if you’re choosing whether or not to feed the SH-9 balanced cables or not.

Iem pairing opinions


I use the OH-10 pretty much as my daily iem for either on the go or relaxed listening. The OH10 still retains it’s warm signature but you can hear a little more detail making its way into the iems. Soundstage sounds a hair narrower but depth is noticeably better. The OH10 does fairly well overall and I had no complaints listening to it out of this amp.

Campfire Andromeda and ADV M5-5D
I run both of these together since they both can pick up the floor noise/hissing fairly easily from an amp, especially when run balanced. I had zero noise from both the single ended and balanced jack. The balanced XLR jack isn’t really balanced but I was still curious if I would still pick up some noise. The original andros felt a little lean in the low end. I still think it does well for an all BA design. I just wish I still had the on board EQ settings that the SH-8 had so I could adjust the sound to fit the andros a hair better. Mids and treble sounded great as they should with the andros. The M5-5D had excellent bass and mids. I love testing gear with the 5D as it handles low end and mids well with it’s bigger DD driver. The other 4 drivers are all dedicated to the higher frequency range which means they get super bright super quick on clinical devices. This was no exception with the SH-9. With that being said, It was simply dipping its toes into sibilance at times. I’ve heard this set get very sibilant on other gear to the point I simply stopped using the 5D with that gear. Using both the SU-8 and iFi NEO helped calm the top end a bit with the 5D. Brighter headphones may wanna think about a warm amp to pair with the SH-9 if they don’t like their top end possibly hot.

Over ear pairings

Dan Clark Audio Aeon “RT” Closed/ LCD2C

I put the poor “RT” through the testing ringer quite a bit. It has started showing a bit of channel imbalance so it got sent off for repair pretty much the day I got the SH-9 in. The little time I got to listen with it was a great experience. It performed fantastically with the SH-9 overall. It lost a little low end due to the pairing at the time which was the SU-9/SH-9 stack. I will adjust my review when I get the Aeons back if things sound different with the other DACs that are warmer sounding. The LCD2C also sounded very good here as well. I barely use them these days since I like the balanced sound of the “RT” Aeons. I never liked what felt like a compressed warm sound signature that my LCD2C produced vs the Aeons. The 2C sounded cleaner than what I was used to once it was paired with the SH-9 stack. Still a warm headphone but I felt like I was getting a little more detail and clarity out of these. Both were easily driven by the SH-9 to volumes I personally like.

Overall thoughts
While I’m bummed that the SH-9 isn’t truly balanced and missing the on board EQ settings of the SH-8, I was still really impressed with the performance overall. My favorite pairing was with the SU-9 DAC. I think the SH-9 does scale really well with any DAC you plug into. I’m happy that for an extra $100 over the SH-8 you get a decent power output upgrade, a better display, the remote and easier to use UI. This is another winner in my book from SMSL and I definitely recommend the SH-9! All my headphones performed outstandingly and my angry/sensitive iems didn’t pick up any noise which was fantastic! Great job to the team at SMSL. Thanks for reading!

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On SH-9 I can put RCA input and get "balanced" headphone output ? On SP200 not possible.
I have the SH-9 in our bedroom setup. It's fed by a Bluesound Node 2i it's connected to a pair of Q Accoustics 3020 speakers & a little Jamo sub and I think it sounds great. My only grip is that it only has the one set of analog inputs as I would like to add another source to it without messing about plugging & unplugging. 👍
Maybe someone has experience: Amplifier SMSL SH-9 + SU-9, will lift, pull HE6 SE?



100+ Head-Fier
For those with experience with the SH-9, can you describe how the relay volume control works while listening? I'm discovering there are several spots where increasing the volume - at least by the number of the screen going up - actually decreases the sound intensity. And then there are other spots where the jump in volume is HUGE, much larger than other increments. Is that how it's supposed to work?