Aiyima T9 - hybrid integrated amplifier

Tubifying Class D amplifiers

[Italian version here]

Product: Aiyima T9 - integrated amplifier
Manufacturer: Aiyima - China
Approx. price.: 130-180$/€
Reviewer: Lucio Cadeddu - TNT Italy
Reviewed: May, 2023

[Aiyima T9 - front view]


This Aiyima T9 is the third integrated amplifier of my comparative test, which has dealt with the Rega Io and the Argon SA1. Actually, these three amps are not perfectly comparable, in the sense that each one has different features, but they have in common similar size and power output. Prices are between 200 and 500€. Technically they differ, since each one represents different approaches: from the traditional, full solid-state Rega Io, to the pure Class D Argon SA1 to this hybrid tubes/Class D Aiyima T9.

Who is Aiyima? It's a Chinese brand which designs and builds many different HiFi components: integrated amps, headphone amps, preamps, DACs etc. They normally use a mix of different technologies, mainly Class D and tubes.

Unlike other Chinese makes, such as Lonpoo and ZeroZone, Aiyima is extremely active online, with a well made and complete website (in English!), with a staff that replies almost instantaneously to queries, an active YouTube channel and warehouses located both in Europe and in the USA. This makes purchasing Aiyima gear extremely easy, with no customs fees or outrageously high shipping costs. Of course, their products can be purchased on the usual online channels such as Amazon, Ebay and Aliexpress.

A closer look

The T9 is an extremely small integrated amplifier based on the Class D chipset TPA 3250 and a tubed preamp stage which uses a pair of Chinese 6K4's. These tubes can be purchased for 5€ at this Aliexpress store, for example. The claimed power output is, as usual, rather optimistic, rated at 100 watts per channel on a 4Ω load. If you take a look at the official data from the chipset manufacturer (PDF linked above) you can discover that the TPA3250, with a 32V PSU, can output 60 watts per channel at 8Ω and 40 watts per channel at 4Ω, at 1% of THD. If we require a more realistic “HiFi” (lower) distortion rate, the power output figures are even smaller. This is continuous power (RMS), while peak power might be different, of course. Now, if you feed the chipset with a lower voltage PSU, like Aiyima did (24V, 4A), these power output figures are no longer valid. Indeed, you might get 40-50 watts per channel on a 8Ω load, which is still a HUGE amount of power, considering the size of this amp, but it is not a 100+100 watter as claimed.

The package also includes an internal DAC which is capable of 24/192kHz resolution on the three available digital inputs: optical, coaxial and USB. There's also a Bluetooth 5.0 input for you to enjoy. And if this isn't enough, add a pair of tone controls, a complete remote, a cool vintage-looking VU meter and even a line output (on minijack) that acts a preamp out (variable, controlled by the volume pot) or a subwoofer out. Only a phono input and a headphone output are missing!

[Aiyima T9 - internal view]

[Aiyima T9 - internal view]

A very unsual feature of the otherwise well-designed T9 is a muting relay that switches the amp off when it detects 10 seconds of silence at the inputs. This muting feature switches the amp back on as soon as it detects some signal coming in. The problem is that its reaction time is slow, so you might miss a couple of seconds of music while skipping tracks on a CD, for example. Moreover, I'm not 100% sure this continuous on/off switching would be beneficial to the tubes or the internal circuits.

After being vastly criticized by several online reviewers/YouTubers, Aiyima has released a new version of the T9, called T9 Pro, which has solved this annoying issue. And while the designer was there, he completely changed the internal circuits as well: new input tubes (now JAN5725) and new chipsets. Have a look at the officially supplied chart below to detect all the differences. Even the power supply is different, since the T9 accepts also 32V now. Actually, it's a completely new amp.

Hence, don't believe what other reviewers say on their useless videos: the T9 and the T9 Pro are completely different devices, and not just because the tubes or the aesthetics are different. Guys, if you don't know how an amp is made, please, please, please limit yourself to publishing a video of the unboxing, since that's the only thing you can do. OK? You do not know the damage you're doing to readers.

[Aiyima T9 vs T9 Pro]

Aiyima T9 vs Douk Audio/Nobsound ST-01

The very same amp can be found under a different brand (Douk Audio/Nobsound) with model name ST-01 or ST-01 Pro. This is not unusual with Chinese HiFi components and, frankly, it is something I don't really understand. Most of the time, when you try to ask for “who does what?”, you don't get precise answers. Perhaps the real manufacturer and designer isn't Aiyima nor Douk/Nobsound, but a third company, and then the unit is re-branded under different names. I've seen a Douk ST-01 inside and, apart from minor differences on the chipsets used, it is the same as the T9. A closer look at one of the motherboards (see pic) unveals the writing “SMART 01”, which reminds me of the model name ST-01. Hence, is Douk the real maker? We'll never know.

Claimed tech specs

[Aiyima T9 - rear view]
Aiyima T9 - rear view

Tubifying Class D amplifiers

[Aiyima T9 - VU Meter]
At Aiyima, they seem to like to mix & match different technologies a lot. The two tubes in the preamp section (mainly a buffer, I'd say) seem to slightly modify the sound of the TPA3250 chipset: I'd consider it an attempt to make Class D more desirable to the masses. Among many audiophiles Class D amps are cold and dry, while tubes are warm and mellow, so a mix of these two approaches should give you the best of both worlds. Or the worst. Indeed, it is true that the overall sound tends to be softer than one might expect from a TPA3250 amp but, on the other hand, in my opinion, the tubes steal some of the vitality of this chipset. You might appreciate it a lot, or not, depending on your taste. Generally, I don't like artificial warmness, since it is, most of the time, just pleasant even harmonics distortion.

As a result, this amp sounds quite different from its Class D competitors, so much so that you wouldn't say it is a real Class D amplifier. Its sound is never aggressive, and lacks the usual transparency and definition of the best pure Class D amps. The bass range is powerful and reasonably extended, but lacks the muscular control and articulation that one might expect. For example, the Argon SA-1 performs better in this area, with punch, articulation and control in spades. With the T9 the bass isn't really lacking, as there's depth and power, but its timing is less than desirable. It seems the rhythm of the bass lines is slower, when compared to the other two amps under test, the Rega Io and the Argon SA-1. One shouldn't forget, though, that the price of these two amps is twice that of the T9.

The mid range is good, there's body and presence, and no evident compression or distortion. It is not as transparent as in the other two amps, but it is pleasant and easy on the ear. The same can be said for the high range, as well, which tends to be smooth and with a slight trace of warmness. I've read of T9 owners who find the high range bright...this is very strange, perhaps the rest of the system or the speakers weren't perfectly neutral.

Perhaps, with different and better tubes this kind of tonal balance might change and even be reverted, but I can't comment any further since I haven't tested different tubes, being no big fan of tube rolling. Actually, if you like to play around with tubes, this amp can be an inexpensive gym where you can train your ears.

Dynamically, the performance is very good, though the bass range, again, doesn't convince me 100%. There's punch, yes, but the correct timing isn't really there. The amp can sound quite loud even with demanding speakers, though I have the feeling it performs at its best quite far from its physical limits. In any case, the T9 can sound quite lively with any musical genre.

In terms of soundstaging, its performance isn't on a par with the other two amps, in the sense that the stage is geometrically correct, but a bit small in size. Moreover it appears more focused and located in between the speakers. Again, I'm quite sure the cheap tubes play a significant role here.

The internal DAC section is reasonably good, but certainly the amp sounds better with an external DAC. This means the amp section is of better quality than the digital section. Oh, before I forget, do not trust reviewers who judge the sound of an amplifier using its Bluetooth input or the USB input with a non-audio optimized PC or smartphone. Sadly, it seems a widespread, bad attitude nowadays. Do you want to know how good is the internal DAC of an amplifier? Use the coaxial or, when this one is lacking, the optical input.

Globally, this amp is surprising, since it offers many features at a ridiculously low price. The other two amps sound better, in my opinion, but cost much more and in one case (the Io), offer far less. The best sounding amp of this trio is the Rega Io, while the SA1 and the T9 are almost on a par. The SA1 is more precise, controlled and transparent, but the T9 is more forgiving on lesser recordings. Hence, it could be a better partner for low cost set-ups that play even lo-fi recordings or compressed music.

Many reviewers/YouTubers swear by the sound of the T9, saying it's on a par with 1000€ integrated amps. This is simply not true. All you need is a 500€ Rega Io to put the T9 to shame. Not to mention the sub-1000€ pair of Tisbury preamp + ZeroZone power amps, which belong to a completely different league. More precisely, as Samuel L. Jackson once said in Pulp Fiction: “...ain't the same fuckin' ballpark, it ain't the same league, it ain't even the same fuckin' sport.” That said, the T9 takes the gold medal for its stellar quality/price ratio.

Complaints & advices

  1. The vacuum tubes need some warm up time, DO NOT JUDGE the sound of this amp before, say, 10 minutes. During the first few minutes it sounds horrible.
  2. The amp's diminutive size and its huge number of features make the rear panel really crowded, with no room left for fingers or thick cables/connectors. Moreover, being lightweight, stiff or heavy cables might flip it upside down easily.
  3. The automatic stand-by shut-off feature is annoying. Luckly, Aiyima have changed their mind with the new T9 Pro. I wonder WHY they decided to include this weird shut-off feature in the first place.
  4. There's no precise “zero” position for the tone controls, and it's quite easy to place the knobs off center.
  5. The vacuum tubes, as said, get warm...and are exposed, no protection whatsoever. This means that children or pets, attracted by the glow, can accidentally touch them.
  6. The power output is high, almost incredible for the size of this amp and, certainly, it sounds louder than many rack-size entry-level traditional amps. In any case, the T9 seems to perform at its best far from its max limit. No, it is not a matter of clipping, it's just the tonal balance that changes a little bit. Do not forget that I'm referring to loud listening levels, with the VU meter constantly near the red zone.
  7. I'd avoid partnering the T9 with lazy speakers (in the bass range) and those with a too warm high range. Well balanced and crisp sounding speakers seem the ideal partners.


The Aiyima T9 is an extremely versatile, nicely crafted amplifier, gifted with a good sound overall. Its many features, its generous power output and low price make it a serious contender for the throne of the best quality/price ratio entry-level amplifier in the market.

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