Hidizs named the S9 Pro Plus “Martha” because “Martha” was the name of the last surviving female Passenger Pigeon, the largest flockingbird species ever to have existed on Earth. After 109 years since the extinction of the Passenger Pigeon, in commemoration of this magnificent species, the professional acoustic brand, Hidizs, has chosen to name their third-generation HiFi Balanced Dongle DAC, the S9 Pro Plus, “Martha.”
S9 Pro Plus Martha adopts the fourth-generation professional HiFi audio processing circuit architecture developed by Hidizs Acoustic Laboratory. This is a fully balanced circuit architecture, consisting of four parts: a USB interface processor, DAC, an independent headphone amplifier, and a POP sound cancellation system. The DAC uses ESS Technology’s flagship DAC chip ES9038Q2M, which uses ESS Technology’s patented 32-bit HyperStream® II QUADDAC™ architecture and Time Domain Jitter Eliminator. It ensures the extremely high accuracy of audio data and represents the highest level of audio decoding technology.
The ES9038Q2M chip supports a maximum 32bit/768kHz PCM sampling rate, ensuring flawless sound reproduction with a high SNR of up to 128dB and ultra-low THD+N of -120 dB.
Hidizs S9 Pro Plus ‘Martha’ is equipped with practical function buttons designed specifically for audiophiles, providing convenient and quick volume adjustments to effortlessly adapt to variations in volume when switching between different headphones. Additionally, the ES9038Q2M offers six filter pulse response effects (PCM FILTER IMPULSE RESPONSE), and the switching function is integrated into two buttons. By simultaneously pressing both buttons, you can cycle through the six filter effects.
Hidizs S9 Pro Plus “Martha” balanced decoding amplifier offers both 4.4mm and 3.5mm audio output interfaces, catering to various headphone types. This design not only maintains the product’s compact and portable characteristics, with a total weight of only 17 grams but also ensures that you can enjoy high-quality music anytime, anywhere. Lightweight and powerful.
The exterior of the S9 Pro Plus ‘Martha’ is crafted from a single block of aerospace-grade aluminum using advanced CNC machining techniques. This ensures a robust and durable design that maintains the Hidizs family’s signature style. It not only looks stylish but also feels comfortable to hold, with a compact and lightweight design that’s both practical and elegant.
Different audio formats, and different visual effects. S9 Pro Plus, under the meticulous design of Hidizs, presents a visual feast of sampling rates. We use vibrant RGB lighting to instantly display various sampling formats and rates:
Yellow: DSD 64/128
Purple: DSD 256/512
Blue: PCM 176.4/192(kHz)
Red: PCM 352.8/384(kHz)
White: PCM 705.6/768(kHz)
Green: PCM 44.1/48/88.2/96(kHz)
The S9 Pro Plus is quite powerful for its size. With 138mW+138mW@32Ω 3.5mm SE and /180mW+180mW@32Ω 4.4mm BAL, it will properly drive many IEMs including hard-to-drive planar or low impedance IEMs, earbuds, and headphones.
In the single-ended PO (3.5mm) output, distortion is as low as 0.0019%, while the balanced BAL (4.4mm) achieves an extraordinary ultra-low distortion of 0.0008%. The signal-to-noise ratio (SNR) is outstanding at 123dB/120dB, and separation reaches 75dB/115 dB. With remarkably low total harmonic distortion, it provides a clean and hiss-free amplification experience.
What’s in the box
ES9038Q2M High-Performance DAC Chip
PCM Supports Up to 32bit/768kHz
Native DSD Supports Up to 512
Physical Buttons for Volume Control & 7 Filter Options
4.4mm Balanced & 3.5mm Single-ended Output
138mW+138mW@32Ω 3.5mm SE / 180mW+180mW@32Ω 4.4mm BAL
Sampling Rate Indication RGB Lighting
Compatible with all platforms: Windows/Mac OS/iPad OS/Android/iOS/Harmony OS
I would like to thank Hidizs for providing me with the review sample of the Hidizs S9 Pro Plus.
As was my experience with other ESS9038-based dongles, the S9 Pro Plus has a very linear and balanced foundation to its sound. This is carried through to the final output with aplomb, offering an almost perfectly even-handed rendition with minimal tonal coloration. I am hearing a slightly revealing top-end but nothing that would hugely affect synergy or polarise for most personal preferences. Rather, it imbues just a little vibrance and zing into its overall image that some may enjoy as it draws greater focus to fine details.
Compared to a high-end source based on similar componentry, transients aren’t quite as defined, and its imaging isn’t so immersive. But the S9 Pro Plus is one of the best hyper-portable sources/dongles I’ve tested when taken as a whole. Surely, the power output is coming into play as well as the S9 Pro Plus does have quite a robust low-end and can keep up with even my least efficient IEMs and many headphones.
Balanced vs Single-Ended Out
It should be noted that balance isn’t a feature you should feel is necessary, as it doesn’t necessarily bring benefits, but rather solutions to issues that are not present here. That being said, if you do have a balanced earphone or the cables to take advantage of a balanced output, then benefits are to be found. With double the output power and a huge jump in channel separation, this is more true here than on many other sources.
I still found the single-ended output to provide a highly impressive sound. However, balance does improve the listening experience further. Staging was the biggest difference to me, you get a noticeably wider and airier stage with greater separation. The background was more resolved and stretched further, creating a more multi-dimensional sound. I would recommend using the balanced output on this dongle if possible, if not, you are still receiving a very accomplished source.
Desktop sources will always be the best foundation of judgment for bass performance as dynamics are tied directly to the power supply, and a larger one invariably has a higher capacitance ceiling. I do notice a drop off in the sub-bass on most portable sources, but the S9 Pro Plus gets impressively close considering the form factor. You won’t get a huge physical slam at the very bottom nor the utmost affirmative note attack relative to a larger source; bass drums aren’t as authoritarian nor rumble as powerful.
However, this remains a tight and snappy low-end with no shortage of audible sub-bass kick. Bass is linear with no apparent emphasis on working towards a well-separated and defined response. Control is well above average for a dongle, note definition impresses as does its ability to discern texture in the mid-bass. As note attack isn’t too aggressive, but this does provide the impression of a smoother bass texture. In turn, its assets are more its dynamics in class combined with its texturing as you will find sharper timing elsewhere.
Like the bass, the listener is instantly able to appreciate a superbly linear midrange rendition that contributes to versatile synergy and overall separation. The S9 Pro Plus has no huge tonal deviations as you’d expect from any decent modern source, though small qualities in its note presentation do imbue certain qualities. For instance, I am hearing a tinge of dryness in its voicing, lacking the liquidity and delicacy of higher-end sources. Similarly, the resolution of fine details operates at a high level but won’t replace your desktop stack. Specifically, the S9 Pro Plus prefers a slightly denser voicing relinquishing articulacy and separation whilst prioritising coherent and well-structured notes.
In turn, it discerns textures well, and instruments are portrayed with a realistic timbre. This is a nicely layered source too, with great contrast between its background and foreground crafting an impressively wide image. However, it doesn’t discern between individual layers such as vocal harmonizations especially well. My main criticism here is regarding organization on complex tracks where the characteristics of its note presentation can make it sound busier than some. This isn’t to the extent that the source sounds colored nor remotely congested, and the S9 Pro Plus remains altogether a clean, clear, and well-put-together source.
As aforementioned, I am hearing a lick of forwardness in the highs, imbuing just a hint more zing than a dead neutral source – such that I would consider SMSL’s high-end gear. To preface, this isn’t to the extent of the infamous Sabre glare you may have heard of coming from their previous generation DACs; I do think the 9038-based sources I’ve tried have all been mostly well-behaved, so this is more a repercussion of individual implementation. The lower treble is impressively even and linear, portraying a well-bodied, textured foreground. There’s a hint of middle-treble emphasis above that slightly lifts instrument clarity and draws greater focus to shimmer, air, and decay.
The presentation is characterized then by its slightly energetic nature but remains free of glare or grit in so doing. That said, this does detract slightly from the initial transient, I do perceive the S9 Pro to have a slightly softer note attack. This means that though it is a well-detailed and honest representation of music, micro-details can get smoothed over more than some. I would suggest this is responsible for robbing the midrange of some articulation as well. Above, headroom is the top level for such a compact source, clearly better than the majority which contributes to strong imaging performance. It won’t give you huge micro-detail and sparkle nor the highest resolution, but a slightly vibrant expression realized through high-class-leading extension.
It’s here that the S9 Pro Plus’s sound makes a lot of sense, it images far better than you’d expect for such a compact source. Many sources can effectively provide a linear sound and detailed lower treble but fall short when it comes to soundstage and layering, providing a superficial experience. The S9 Pro Plus is no such creation, delivering out-of-the-head width on the right IEMs and a good amount of depth too, forming a multi-dimensional image. It remains width-biased, but I was impressed by its dimensions combined with its neutral note size.
Specifically, there’s a palpable air surrounding each element often absent from competitors. Again, layers are well defined, and the background isn’t super detailed, but does showcase impressive width. Separation is likely its weakest link, with note definition lagging slightly in the treble (somewhat counterbalanced by its tonality) and the bass and midrange being more structured over ultra-concise. It’s not a poorly separated sound, aided by the larger stage, but not the best I’ve heard.
Is the Plus model an upgrade compared to the previous model S9 Pro? It comes with a cheaper price tag, and also with the same ESS DAC chip inside. Still, the answer is yes. Because the S9 Pro Plus has a more mature tuning and has the missing volume keys. Sadly still no App support, maybe next time.