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KingRex UD-01
Special Edition

NEW! There's little wrong with a stock UD-01: tonal balance, detail retrieval, transparency, organic musicality . . . all the things cheap DACs don't usually do well, the UD-01 does brilliantly.

Naturally, then, we wanted more: bigger soundstage, better dynamics, more information, increased vavoom. So we junked the £2.50-worth of dual channel op-amps installed in the standard unit, and installed four of the finest op-amps we could squeeze in the case: Burr Brown's flagship OPA627s at £18 a pop. It takes two of these peerless single channel op-amps to do the job of the TL072 in the DC section, and another two to replace the low pass filter OPA2604.

In truth, we auditioned (what felt like) every op-amp on the market, seeking some special chemistry among lower priced items, but, as many reviews have testified, the combination of huge soundstage, vivid dynamics, smooth midrange and treble and bottomlessly articulate bass bowled us over.

Additionally, the scary-bright blue LED is removed, case dampening is added, and a strategic scattering of Stillpoints ERS fabric is added.

The Special Edition UD-01 is a truly high-end DAC with a tiny form factor. The KingRex PSU or other upgraded power supply is strongly recommended to get the best from the UD-01 SE.

Please note that the SE upgrade can be retrofitted to a standard KingRex UD-01 for just £65 including postage.

Compatible with any Windows, Mac or Linux PC.


We no longer recommend adding an expensive PSU to the UD-01 – better to spend less for greater benefits on the UD-01 Pro with its on-board linear supply. However, all these DACs clearly reveal differences in USB cable . . .

KingRex UD-01 SE + 1m LAT USB Cable: £229
UD-01 SE + 1m Wireworld Starlight USB Cable: £259
UD-01 SE + 1m Locus Polestar USB Cable: £359
UD-01 SE + Audio Odyssey TOD2X + LAT USB: £459


“I'm also going to go out on a limb here, because I'm going to enthuse about a 65 quid upgrade on a £160 DAC . . . But, anyway, I've just had one of those fantastic hi-fi moments when you hear loads of stuff you've never heard before on familiar recordings.

I've been having a love affair with a Taiwanese DAC for a bit over a year. The KingRex UD-01 is £160 in its basic form – about the size of a ciggy packet, I suppose, with a wall-wart power supply. Let's skip over that. I had the UD-01 with the KingRex Power Supply; £170 in a very nicely engineered metal box, which is where the UD-01 starts to punch above its weight.

Item's Mark Welsh talked me out of going for the SE II upgrade, and instead took about half the amount off me I'd budgeted for. He sold me an SE upgrade and a bling audiophile USB cable that I haven't plugged in yet, having decided to let the SE burn in thoroughly before making any comparisons. He says the SE II and the SLAP (the sealed lead-acid power supply) both make further improvements, but the law of diminishing returns sets firmly in, and in the context of a conversation about my next upgrade and the KingRex's future in my office system, spending less now seemed to make a lot of sense.

The UD-01 SE I'm listening to at the moment was a new (as in unused) DAC and, along with the new op-amps, needed 100-150 hours burning in – a quick calculation tells me it has had between 100 and 150 hours. Strangely, at a little over 100 hours, everything suddenly came together.

To be honest, I'd been a bit worried that the wonderful naturalness of the base UD-01 had been replaced by something that sounded more hi-fi. The SE seemed to be getting further bass extension, detail throughout the range and a more focused stereo image, but didn't seem to be shrugging off its early tonal dryness.

This evening, though, the SE sounds like the base model, but with a much cleaner window. That means the SE should pass the most important uglymusic hi-fi test – it doesn't irritate me over a long period – with flying colours.

So what's the newly-buffed, smear-free window contributing to my enjoyment? I've noticed tiny nuances as big, heavy cymbals are played - Charles Moffett's playing on Ornette Coleman's At The Golden Circle has moved from being a bit crude to showing real sensitivity. Similarly, I've heard details in Ron Carter's acoustic bass playing on Joe Henderson's The State of the Tenor that just haven't been there before, even when I've had much bigger speakers in the system in the past. I've also dipped into Joy Division, Pearl Jam, John Abercrombie and Nusrat Fateh Ali Khan, all with the same post-Windowlened wonderfulness.

What's so impressive is that the SE is finding all this extra detail without sacrificing any of the poise, musicality and rightness of the original.

So £395's worth of DAC, upgrade and power supply isn't cheap cheap, but even the base model and power supply haven't disgraced themselves at any time feeding a system that should be way out of its league.” – David Rosam

“Clearly an improvement on the stock configuration, sounding better in almost every department. It simply sounds more sophisticated than the stock UD-01 . . . I can recommend the 'SE' as a worthwhile upgrade over the standard UD-01.” – Nick Whetsone, TNT Audio

“These 2 single channel op amps [twin OPA627] absolutely trounced anything that had gone before them in this test: the width of the soundstage, the clarity and the sheer presence make this my choice of op amp for use in the Chiarra without a shadow of a doubt. The sound is just so "clean", "natural", musical" and "detailed" with the 627's on board. Ten out of ten.” – Rock Grotto

KingRex UD-01 Special Edition DACKingRex UD-01 DAC Rear panel

  • Decoder chip: Burr-Brown PCM 2702E
  • 16-bit 44.1 or 48kHz
  • Low pass filter op amp: twin Burr-Brown OPA627
  • DC Servo: twin Burr-Brown OPA627
  • Coupling capacitor-free design
  • Power rating: DC 12V / 0.5A
  • Adaptor input: AC 100-240V (47-63Hz)
  • Gold-plated RCA SP terminals.
  • Single USB 1.1 input.
  • Comes with UK transformer / power lead.
  • 12 month UK warranty
  • Weight: 207g
  • Dimensions: 110mm x 75mm x 33mm



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