HiBy RS6

HiBy RS6 Review

Select Comparisons

For our comparison work, we decided to keep it all R2R with a comparison of the 3 DAPs currently available that use this technology.

Note, LP has both the P6 and the P6 Pro but we prefer to use the P6 Pro as our point of comparison due to the touch OS. The choice of the Hifiman R2R2000 Red over Black is due to relative pricing.

Our selected monitors for the comparison work include the UM MEST MKII, Campfire Audio’s Andromeda 2020, and the 64 Audio U18s

Cayin N6ii & R01

$1818 (combined price if bought separately)

Technical

The N6ii is getting a bit old now having been launched in mid-2019 and not as an R2R DAP, (A01 delta-sigma motherboard). However, with the introduction of the new R01 motherboard, the N6ii stands right beside the RS6 as the only Android-based R2R DAP. 

Both the RS6 and the N6ii/R01 use a discreet ladder DAC implementation with 48 tightly matched resistors per channel (1/1000) with a digital bridge before the DAC for processing whereas the RS6 is more expansive with the Darwin architecture. That includes additional features such as OS/NOS, Harmonic Controls, and the use of other DSP functions such as the IEM presets. 

For traditional decoding, they are fairly even with both capable of bitperfect DSD256 and PCM 384kHz for all formats except WAV where the RS6 has an advantage with 768kHz capability. The other unique differentiator is the ability of the RS6 to unfold MQA up to 4X on the digital side and 16X on the analog side. The R01 has no MQA unfolding capability. 

Raw output power is better for the RS6 going balanced at [email protected]Ω compared to just 430mW into the same load with the R01. For SE, the opposite is true with the N6ii faring better at [email protected]Ω compared to the [email protected]Ω rating for the RS6.

The RS6 is the more powerful of the two for demanding headphones going balanced, however, it is not so clear cut for SE. The power rating is more than adequate for most modern monitors these days.

Rather I would look to the performance numbers of both DAPs where the R01 has a 17dB dynamic range advantage for both balanced and SE outputs. Both are very close to each other for distortion control, (THD+N and SNR) however. 

Cayin R01

Design

The RS6 is the slimmer, longer, and wider of the two DAPs with a larger 5″ IPS panel as opposed to the 4.2″ version on the Cayin N6ii. However, it is also the heavier of the two DAPs weighing 45g more than the Cayin as well as running hotter during use. 

The RS6 also offers dedicated balanced and SE line-out with 2V and 4V ratings whereas the N6ii is PO-only with 4.4mm and 3.5mm options. On the flip side, the N6ii can offer I²S as well as USB-DAC, OTG, and coaxial via USB whereas the RS6 has no I²S capability.

Given the launch date and the lower-tier Snapdragon 440 inside the N6ii, it is no surprise that its Android 8 platform is a bit slower. Our AnTuTu measurements back that up with the RS6 getting a score around 4 times higher than the N6ii. 

The R01 does not hugely alter the core N6ii player DSP options either with no DSD or LPF filtering options that the RS6’s more advanced Darwin architecture can offer. 

One key advantage for the N6ii/R01 is battery life with a larger 5800mAh battery inside offering around 50% more battery life at 12.5 hours SE and 11 hours balanced. The RS6 struggles in this department with 8 hours or less going SE and lower for balanced. 

Performance

Some definite differences here and where you prefer lies might lie in how much warmth and vocal presence you prefer or if you are a highs and lows guy.

The R01/N6ii lower pitching instrumental bass fundamental is more noticeable compared to the RS6. That is not to say the R01 extends deeper or has more sub-bass amplitude. I actually think both of these extend quite well with an excellent bass response.

Rather, the RS6 midrange is more elevated and closer sounding whereas the R01 leans back a little in the mids with more treble emphasis producing a lighter note with more odd harmonic sheen, especially in the upper mids. That produces a bit of a clearer separation with more contrast on the R01 allowing the bass fundamental a bit more space to shine.

The RS6 sounds more linear from the bass through to the mids, arguably more coherent but not quite as airy and expansive. There is less treble presence in the RS6 performance paired with the likes of the MEST MKII and the U18s so notes err more to an even harmonic warmer coloration. Nothing lush or smoothed over but definitely more rounded and richer.

The staging of the R01 throws out a bit more extension also from that stronger treble presence with the paired IEMs. That little uptick in sparkle does help tease out higher pitching spatial cue presence that can split your attention between the fundamental and the upper mids/highs giving you a perception of enhanced width and height. 

The RS6 on the other hand draws your listening more to the bass through the mids and peaking with that gorgeous vocal timbre. It is comparatively less holographic, more intimate in ways but perhaps with a stronger focus on vocal presence. 

HIFIMAN R2R2000 (Red)

$999

Technical

The R2R2000 comes in two varieties, the dual 24BIT PCM1704K Black and the dual 20BIT PCM1702 Red version. Both are often referred to as R2R units but in this case, the HIFIMAN units are multibit non-oversampling chipsets rather than discreetly engineered resistor ladders such as the one inside the RS6.

The PCM1702 is effectively two 19-bit DACs in a complementary design which negates potential zero-cross glitches on its waveform pattern that earlier R2R DAC suffered from.

Its decoding is a little lower compared to the RS6 at PCM 24bits 192kHz and as a DAC via USB-C up to 24bit/384kHz and DSD64. The Red also lacks any MQA unfolding or rendering. The RS6 is much more capable with its alternative DSD Darwin architecture design offering up to DSD256, PCM 384kHz, (PCM 768kHz WAV), and MQA up to 16X. 

The R2R2000 Red has two sound modes, eco, and HiFi mode, primarily aimed at reducing battery strain or maximizing sound output. However, it lacks the depth of the RS6 Darwin Controller presets, nor does it have any option for NOS on its DAC.

Both amps inside are opamp based with the Red capable of up to 500mW for balanced and 320mW for unbalanced output power. SE is a fair bit stronger compared to the 180mW rating of the RS6 but slightly weaker for balanced compared to the 690mW rating of the RS6.

Hifiman R2R2000

Design

The big plus is the size of the R2R2000 Red. It is far smaller, more pocketable, and lighter than the RS6 at just 142g compared to 335g.

However, in terms of UI and features, the RS6 has a lot more in that bigger body. That includes a 1080p touchscreen, full touch control, Android with wireless and wired expansion and functionality, as well as more in-depth DSP and sound-shaping options.

The R2R 2000 RED OS is not touch-capable outside of the control buttons. It has a very linear operation with text-based indicators only and is a bit laggy at the same time in terms of accessing files from a memory card. It also lacks onboard memory of which the RS6 can offer 64GB. 

Both offer a line-out option though the R2R2000 is not dedicated with only a 4.4mm balanced LO whereas the RS6 has a dedicated 3.5mm and 4.4mm LO option.

We do have to be aware, however, that the R2R2000 was never marketed as a fully-featured DAP, rather a BT streaming device, so it is not surprising that the basic HIFIMAN OS is nowhere near what we would expect from a modern DAP.

Whilst it lacks WiFi, the BT of the Red performance is pretty good which seems logical given its streaming pitch. Both offer LDAC receiving though the R2R2000 can only offer BT4.2 compared to BT5.0 on the RS6. The R2R2000 can also offer LHDC decoding and is on par with LDAC at 900kbps capability whereas HiBy opts to use their own super-fast but niche UAT codec.

Neither offers a great battery life with a default eight hours for each but you can greatly expand the R2R2000 battery life by opting for Eco mode with up to 30-35 hours. 

Performance

If the RS6 is comparatively warmer sounding than the R01, then the R2R2000 Red makes the RS6 sound relatively balanced and neutral. Also, whilst I find the tonal coloration of the Red to be smooth, non-fatiguing, and very ear on the ear there is quite a gap between these two in terms of technical capability.

The RS6 sounds more spacious with better staging width and headroom also. The Red has more bass bloom so it sounds planted, warmer, and more voluminous and I dare say most will feel it has more weight there also.

However, in doing so it pushes down on the mids and vocal presence a lot further giving it a comparatively veiled and less balanced performance when up against the RS6. If you are using a dynamic driver or hybrid monitor you are going to hear that additional bass weight and bloom quite easily.

The RS6 has a better bass to mids balance and sounds more coherent as a result. Mids are more open sounding with improved instrumental presence and separation. Further, there is more treble presence from the RS6 which gives its harmonic balance a little more of a lift compared to the very smooth and almost lush-sounding R2R2000 Red.

The Red is more suited to medium efficiency IEMs with a bit of brightness that needs taming down whereas the RS6 is more flexible for tonal pairing. The improved noise floor and less gain hiss also make the RS6 the more natural choice for super sensitive IEMs such as the Andromeda 2020.

Luxury & Precision P6 Pro

$3899

The final R2R DAP is probably the benchmark for R2R performance currently in the market today but with a price far in excess of the RS6, the LP P6 Pro

Technical

Both DAPs offer a discreet 48 resistor per channel R2R DAC implementation, though the P6 Pro lacks the OS depth and Darwin Architecture with the RS6 such as the IEM presets and Harmonic controller. 

Decoding capability remains unchanged from the P6 Pro and that’s good news for RS6 owners as both have a ceiling of 32BIT/384kHz PCM and DSD256. The RS6 will have a decoding advantage is for WAV files at 768kHz and it does also offer MQA unfolding to 16X which is not possible on the P6 Pro. 

Luxury & Precision may not have a Darwin controller or a complex OS but what they did focus on was their discreet Class A amp topology instead of using opamps.

The headline output numbers do look similar at 700mW from a 32Ω load balanced and 180mW single-ended compared to 180MW SE and 690mW balanced for the RS6. However, the numbers just behind those tell a different story with the P6 Pro SNR rated at 125dB or 11dB higher than the RS6 and a dynamic range in excess of 118dB compared to just 95dB from the RS6. 

Both do have a line out but the RS6 is dedicated 3.5mm 2V and 4.4mm 4V whereas the P6 Pro is dual PO/LO with a gain switch function between 1.55V and 2.45V output which is more SE voltage levels. Both also offer digital outs with SPDIF for the P6 Pro and USB-C to coaxial for the RS6.

Luxury & Precision P6 Pro

Design

The P6 Pro is a bit boxier and taller than the slimline RS6 but it is a fair bit lighter at 248g compared to 335g and you can feel the difference when handling.

Both have modern minimalist styling but the focus on the RS6 is more on that excellent IPS 5″ panel whereas I prefer the general aesthetic of the P6 Pro with its wood back panel, executive black, and better-positioned potentiometer. It just feels more intricate in its milling and finishing.

The P6 Pro G+G capacitive touch LCD panel is much smaller and almost entirely text and lined based with only the only graphics on the playback screen. Nowhere near as user-friendly or as expansive as the touch Android 9 OS on the RS6. It lacks any WiFi or apps expansion and should be classed purely as a music player with BT wireless receiving capability.

BT functionality on both is good with LDAC decoding. However, BT is more functional on the RS6 with HiByLink and Android apps expansion whereas the P6 Pro is purely for audio receiving.

Both DAPs do have a NOS function which I know a lot of people prefer, including myself. The P6 Pro does also have some further presets such as a few digital shaping filters and a choice to go DSD native or decode to PCM. 

You get 64GB of memory with both DAPs as well as a single microSD card expansion though the P6 Pro lacks OTG for any further expansion and the cards must be in FAT format only. You honestly do not need OTG digital audio with the P6 Pro, its performance would be better than any dongle. 

Performance

It might not seem fair to pitch the flagship P6 Pro in with the cheaper RS6 and yes, you would be right in thinking that the P6 Pro is the better performer. However, sometimes preferences are what they are, and given their differences some might prefer what I would term the more overt coloration of the RS6. 

Both of these were compared in NOS mode by the way which is where I think the magic of R2R really shines. On this basis, both do very well in fleshing out the instrumental and vocal texture, and neither sound delta-sigma as in overly polished. 

However, in terms of timbral balance, the P6 Pro has that resolving reference sound with a more accurate life-like harmonic balance. It takes a dash of that R01 sparkle but keeps the weight throughout so bass slam is equally as good, and mid-note physicality or girth is just as noticeable.

The RS6 is not quite as vivid sounding or as controlled on the bass and from the above, you can assume the P6 Pro is not as warm or as overly analog through the mids either. The original P6 might be closer in terms of coloration to the RS6 in that regard but not as weighted on the bass as the RS6. 

Dynamics is also a good talking point here because you can really pick up on that improved dynamic range backed by the paper ratings. Loud to soft is palpable with tons of resolution and excellent layering.

The RS6 can sound a little more compressed with slightly less separation but it compensates with that smooth analog-sounding vocal timbre presence which is where I think it does particularly well.

HiBy RS6

Our Verdict

The HiBy RS6 is a deeply engaging and well-thought-out initial foray into the world of portable R2R Android DAPs.

It is definitely a flavor specialist though with that smooth and slightly dense tonal coloration so I cannot see this appealing to the neutral lovers but for vocalists and fans of that analog sound, this should be right up your alley.

The ground-up conceptualization of Darwin and what it means to the portable audio user is probably the most salient aspect of all its features with that blazingly fast OS workflow already a staple of previous HiBy product releases. 

You get so much depth and tweakability to the stock sound, be it overtly from MSEB or on a more nuanced level with the IEM presets. Options that could keep you involved and discovering new presentations for a very long time. The fact that HiBy can add to it with more and more profiles gives the RS6 some potential legs to its product lifecycle also.

Kudos to HiBy for bringing out an R2R DAP on the Android platform. It presents a nice alternative to the Cayin R01/N6ii and a different sound signature also which can only benefit the potential buyer in the end. Definitely, a worthy introduction for those analog lovers whose wallets simply will not go as deep for the excellent LP P6 Pro.

HiBy RS6 Specifications

  • SoC: Qualcomm Snapdragon 660
  • CPU: 8-Core Kryo 260, 2.2GHz
  • GPU: Adreno 512
  • DAC: Darwin Architecture
  • 5” Full HD 1080P display
  • RAM: 4GB
  • ROM: 64GB
  • MicroSD Support: <2TB
  • Pure Copper body
  • Battery Capacity: 4500mAh
  • Battery Life: Up to 8.5 hours

Output Parameters(3.5mm)

  • Frequency Response: 20Hz-45kHz
  • Output Voltage: 2.4Vrms
  • Output Power: [email protected]Ω
  • Crosstalk rejection: 72dB
  • SNR: 114dB
  • DNR: 95dB
  • THD+N: 0.003%
  • Output Impedance: 0.4Ω

Output Parameters(4.4mm)

  • Frequency Response: 20Hz-45kHz
  • Output Voltage: 4.7Vrms
  • Output Power: [email protected]Ω
  • Crosstalk rejection: 98dB
  • SNR: 114dB
  • DNR: 95dB
  • THD+N: 0.003%
  • Output Impedance: 0.8Ω

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