Review: HiBy RS2 – R2R To Go

Hardware specs

For all the talk of software, hardware is where the rubber meets the road, so to speak. RS2’s smaller footprint means you’re unlikely to get a muscle car engine under the hood, and while that’s mostly true, RS2 still packs plenty of audiophile-grade parts into its diminutive shell. 

For reference, here’s a quick list of the main hardware specs, and I’ll discuss some of the more important ones below:

  • CPU: X1000E
  • DAC: Darwin discrete R2R
  • Supported formats: PCM384 / DSD256 and MQA 8x
  • Interface: USB-C (USB 2.0)
  • Screen: 2.45” 480×360 touchscreen
  • Storage: no internal storage / 2x Micro SD card slots (4TB max combined)
  • Battery: 3500maH (3 hour charge time, approx. 10 hour playback)
  • Chassis: brushed aluminium and glass
  • Output voltage: 2Vrms (3.5mm PO/LO), 3.2Vrms (4.4mm PO)
  • Max power output (@32Ω): 125mA (3.5mm PO), 320mA (4.4mm PO)
  • Crosstalk rejection: 63dB (3.5mm PO), 82dB (4.4mm PO) 
  • SNR: 118dB (3.5mm PO), 117dB (4.4mm PO)
  • Dynamic range: 82dB
  • THD+Noise: 0.006%    
  • Output impedance: 0.47Ω (3.5mm PO), 0.94Ω (4.4mm PO), 10K (LO)

I‘m not one to go by measurements, but it was clear from my testing that output from the 4.4mm balanced port was cleaner and more dynamic than the same output from the 3.5mm port when volume matched. HiBy DAPs have generally favoured balanced output in the past, and RS2 is no different, although 3.5mm performance is still excellent.

For a DAP this size, RS2 has a fairly large battery, enough for 10 hours (10.5 hours in my testing) hi-res playback, and 40 days of standby time (I didn’t test this but I can say with certainty the battery hardly ever depleted while in standby mode).

It also features an oddly squashed screen, but since I already mentioned this earlier, I won’t belabour the fact here. I will say that, given the battery size, I‘d have gladly sacrificed an hour or two of playback time for a full-size screen. Thankfully the screen is very responsive to the touch, and the basic processor is more than enough to make the interface feel snappy. Scrolling is relatively fast, although adding a card full of music files to the database can take quite a bit of time, and is slower to navigate than on a fast Android DAP. 

What the specs don’t show is some of the high-grade audio hardware inside the RS2. The output stage is handled by a Ti OPA1652 and 2x OPA1612 chips for low pass filtering. Two ‘flagship class’ OPA1622 chips take care of the amplification stage for four independent channels of current mode headphone amplification, and a pro-grade NJW1195A digital volume controller is used to precisely attenuate the output. 

Along with the discrete R2R array and 256-tap FiR filter, this is far more audio muscle than you’ll get in even the most expensive smartphone, which is reason alone for getting a DAP in the first place. 

That said, power output isn’t class-leading, though with an effective 250-odd mA available from the balanced port (at <1% THD), RS2 is more than powerful enough to cleanly drive – and control – just about any IEM on the market today. You might even get away with using sensitive headphones, but I’d caution against trying to use larger headphones with a small DAP unless you don’t really care about maximum sound quality.  

It’s interesting too that HiBy chose not to include built-in storage, although this isn’t completely uncommon, even with higher-end DAPs. It does help keep internal circuitry to a minimum to reduce electrical noise, and allows you to use ultra-low noise cards (if you believe in that sort of thing) to maximise performance. Of course, it helps to keep the price down too, especially when you’re launching the first-ever entry-level, ultraportable R2R DAP on the market. 

Continue to Sound impressions



Guy Lerner

Guy Lerner

An avid photographer and writer 'in real life', Guy's passion for music and technology created the perfect storm for his love of portable audio. When he's not playing with the latest and greatest head-fi gear, he prefers to spend time away from the hobby with his two (almost) grown kids and wife in the breathtaking city of Cape Town, and traveling around his native South Africa.


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