Hiby R6 Pro 2nd Gen

A modern-day music player is so much more than its DAC chips, and HiBy have taken that to heart … hoping everyone does too, to truly see the extent of their efforts. Greatness achieved at the highest end is easy, but portable digital audio has a new master in HiBy because of how much of that essence trickles down affordably into R6 Pro II.

HiBy’s effort means R6 Pro II is greater than the sum of its parts regardless of its entry price, and ensures the very best platform for Asahi Kasei Microdevices (AKM)’s resurgent flagship DACs to make their mark.

That’s evident because of the mastery HiBy designed around AKM's digital ecosystem. These Japanese giants, back on their feet with a clean slate, started afresh expanding the basic footprint of a single DAC chip IC into three separate parts – to similarly multiply capabilities by a factor of three.

AKM’s AK4191EQ DSP is the brains of the operation, receiving pristine I2S clocking and data from HiBy’s FPGA. Aboard, AK4191EQ’s delta-sigma modulator takes advantage of its expanded, dedicated, silicone footprint to lay claim to the title of the first chip IC working at seven bits.

These seven single-bit modulators flow on into R6 Pro II's AKM 4499EXEQ DACs, one for each channel and built with a single purpose in mind: to turn the interpolated, noise-shaped, digital data it receives into the most precise analog waveform possible afforded by its large footprint.

Silicone size matters when it comes to a great DAC IC, and AK4499EXEQ has it. Enabled by much more exact, matched resistors and capacitors aboard for precise DC single-bit decoding, and dynamic element matching that is less burdened by switching errors – granted by parts accuracy from a bigger footprint.

Any conversion errors from AK4499EXEQs outputting in current manifests as DC offset, and not total harmonic distortion, that is easily filtered out. That's expected of any source claiming to be high performance.

HiBy's eight-channel current-to-voltage I/V section follows these AK4499EXEQs, befitting of chips that output in current for best distortion performance and indeed more expensive players.

By treating each of the eight channel current outputs separately before stereo summing, R6 Pro II yields a small-signal stage that is transparent and, most importantly, accurate. HiBy's gain signal flows as a linear waveform on to a series of eight discrete bipolar power transistors working in Class AB or an optimally pure Class A.

Differentiating itself from so many others who use op-amp ICs with inordinate amounts of gain, R6 Pro II's open-loop linearity remains excellent before application of feedback. That's owed to its Class A bias ensuring individual output transistors are working in optimum condition – aided by an operating voltage of five volts. Distortion and noise are kept low, without resorting to the excessive use of negative feedback.

HiBy designed a true-balanced differential amplifier to further improve R6 Pro II's linearity, and you can count on common-mode rejection at its best whenever you plug in via 4.4mm.