To preface, the vast majority of modern sources will provide a linear FR and neutral sound. I find, in my personal experience, that the source affects the presentation more on the micro than macro scale mostly coming down to slight differences in note presentation. Of course, some sources deliberately do not target neutrality and will offer some colouration.
Within this scape, the original Tone Board was lauded for its mature ESS implementation at entry-level pricing. Though I do find my higher-end DACs more resolving and spacious, the Tone Board has especially strong detail retrieval and linearity for a source of its price. I found it was defined by its sharp transient response that contributes to the aforementioned qualities. The Tone 2 Pro is unsurprisingly cut from the same cloth given the identical choice of DAC chip. However, some advancements have been made with measurable benefit being evident. In subjective listening, it presents very similarly, with an almost identical tonality and balance, targeting a neutral and linear sound. However, the Tone 2 Pro definitely does offer an iterative jump in performance over its cheaper sibling.
It makes most sense to me to evaluate this first as a pure DAC given the Tone Board was such a popular option. Connected to my THX789 via a splitter and cycling through sources using SoundSwitch, I was able to AB the two closely.
Disregarding comparison, buyers can expect a highly neutral tonality and almost perfectly even sound bottom to top from the Tone 2 Pro when used as a DAC. There is no brittleness or ringing as some past ESS sources have been prone to, but an impressively even-handed experience. It sits a touch on the engaging side like its predecessor, with a slightly more aggressive note attack that contributes to a defined and hard-hitting presentation. The prime differentiator is the Tone 2 Pro’s soundstage presentation which is markedly improved. The soundstage is appreciably larger in all axis and the imaging is noticeably sharper and more multi-dimensional.
It has an improved ability to position coronally where the original tended to offer more of a lateral spread of elements. In turn, the Tone 2 Pro provides a more involving and immersive listen. Compared to a higher-end source like the SMSL SU-9, the Tone 2 Pro simply offers a sized-down version of the same experience, where I felt the Tone Board’s more two-dimensional image was a prime quality that cemented its status as a lower-tier product. In turn, the Tone 2 Pro can be more easily enjoyed in isolation, as its flaws are mostly only apparent in direct comparison to higher-end gear. Similarly, the treble presentation has lost some of its hard-edge, offering a more textured presentation with a bit more timbral accuracy.
This contributes to a noticeable jump in fine detail retrieval. On the flipside, there are some caveats relative to the original simply due to the nature of the changes. Primarily, the Tone Board’s more intimate presentation is more focused. Its treble is crisper and more aggressive, similarly, its sub-bass appears slightly bolder and harder hitting. It remains that I believe the Tone 2 Pro offers a more holistic representation of music whilst retaining the lauded tonal accuracy of the original. To me, this is a winning combination and a welcome refinement of an already strong approach.
DAC + Amp
Of course, the Tone 2 Pro not only represents a performance bump over the original but also introduces extended functionality with its in-built amp section. With no internal battery, output is naturally limited to the power output of the USB standard. I did test the device with and without a linear power source and heard minimal difference in my testing. Your mileage may vary depending on the quality of the USB data + power input, that said.
The Tone 2 Pro offers a slightly more mid-bass focused low-end that is warm with slightly plump notes. It doesn’t have the hardest hitting sub-bass, but still offers a well-controlled response that upholds good separation and definition. Attack is slightly quicker which aids this while decay is natural which, in culmination with the warmer mid-bass, provides a slightly smoother texture. The midrange is fairly transparent and isn’t overly warmed by the bass. Though it is imbued with a hint of smooth and full-bodied character relative to my THX desktop amp.
Treble is organic with excellent body and texture, a standout quality of this device. There is a clean transient response with strong fine detail retrieval in the foreground and a rich, natural timbre alongside accurate positioning, being neither forward nor recessed. There was a bit more sparkle and micro-detail on the desktop source but not as much difference as expected. The THX amp does have a noticeably cleaner background so its presentation feels grander and more composed as a result. The Tone 2 Pro is no slouch, however, as though it lacks the same liquidity, it remains a smooth and organised performer with an especially faithful treble representation that belies its asking price.
In terms of soundstage, the desktop amplifier has an obvious advantage and, unfortunately, the integrated amplifier is unable to fully take advantage of the DAC’s abilities here. There is a noticeably smaller stage that retains a good amount of depth but has limited width. Still, imaging is sharp with a nice lateral spread albeit minimal coronal positioning. Layers are well-defined and separation isn’t harmed at all by the bass warmth in totality given great linearity is upheld elsewhere.
Unfortunately, I didn’t receive the Khadas balanced RCA cables for this review so I was unable to test balanced output from the DAC. However, testing the balanced headphone out, I was still able to benefit from its increased output power. This is immediately evident with a jump in volume alongside a slight boost to dynamics and sub-bass power. The balanced output also provides, to my ears, a slightly more spacious presentation. The effects are most pronounced on less sensitive gear and can mostly be attributed to the increase in driving power. This is recommended if you intend to use the Tone 2 Pro as an all-in-one for full-size headphones, as it will give you a good jump in volume and dynamics.
I compared the Tone 2 Pro to my THX789 fed by the original Tone Board for maximum congruency, volume matched with an SPL meter. I listened to the Audeze LCD-X which is an efficient and resolving full-size planar headphone. The results were impressive, on high-gain especially, there was easily sufficient volume for my ears. Bass extension was good as was overall balance. The desktop source provided a slightly more extended and harder-hitting sub-bass while the Tone 2 Pro offered a slightly fuller and warmer mid-bass. Control was appreciably better on the THX amp, the mid-bass sounding more defined and articulate. For more difficult to drive headphones like the Focal Clear (55-ohms), I did miss a bit more sub-bass power relative to my desktop amp, that was only partially redeemed by switching to the balanced output. The Tone 2 Pro is evidently best paired with IEMs and more efficient headphones as a result but does in a pinch with plenty of volume but just enough driving power for more difficult full-size headphones.
Output Impedance & Noise
Both the balanced and single-ended outputs provide a low output impedance under 0.3 ohms. I confirmed this using the Campfire Audio Ara which employs a mechanical crossover and very low 8.5 ohm impedance that makes it especially source sensitive, benefitting even from a sub 1-ohm OI. The Tone 2 Pro offered an ideal result here, staying true to its specification. The Ara sounded smoother and slightly fuller from the Tone 2 Pro than even my THX789 with 1-ohm impedance, suggesting that the output impedance is indeed under 1-ohm. In addition, I observed zero background hiss even on my most sensitive IEMs, making this source ideal for multi-driver models in addition to low volume listeners.
The Tone 2 Pro is not positioned quite like its progenitor given the substantial increase in pricing. No longer can it be lauded as an overt value champ as it now sits about on par with the competition. And yet, the diminutive form-factor and expanded functionality have not come at the cost of performance nor refinement. The Tone 2 Pro introduces a gorgeous design and sturdy build alongside a satisfying weighted rotary encoder that is a pleasure to use. The menu navigation is slightly convoluted but reliable to operate once the user becomes acquainted. Meanwhile, the sound represents a refinement of the already excellent Tone Board, with the same emphasis on neutrality now bolstered with a more natural timbre and spacious, multi-dimensional soundstage. It represents a real step forward that is easy to appreciate and remains hard found even at its higher asking price. The integrated amplifier inspires less, especially considering how strong offerings in the $100 price tier have become. It lacks the power, spaciousness and versatility of these models but is redeemed with a black noise floor and extra low output impedance in addition to the general portability of the device. Accordingly, even at its elevated price tag, the Tone 2 Pro remains an excellent DAC paired with a simply good integrated amplifier that does well for IEMs and suffices for headphones.
The Tone 2 Pro is available on HiFiGO (International) for $199 USD at the time of writing. I am not affiliated with Khadas or HiFiGO and receive no earnings from purchases through this link.