June
2020

Country of Origin

Korea

X7-DDC Femto

Reviewer: Srajan Ebaen
Financial interests: click here
Sources: Retina 5K 27" iMac (4GHz quad-core with Turbo boost, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 14.4), PureMusic 3.02, Audirvana 3, Qobuz Hifi, Tidal Hifi, COS Engineering D1, Denafrips Terminator, Soundaware D300Ref,  AURALiC Vega 
Preamplifier: Vinnie Rossi L2 Signature with WE VT52/300B or Elrog 50/300B, Nagra Classic, Wyred4Sound STP-SE Stage II, Vinnie Rossi LIO (AVT module)
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1 monos, SIT3, F5, F6, F7; Goldmund/Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics NC500 monos; LinnenberG Audio Liszt monos
Loudspeakers: Audio Physic Codex; Cube Audio Nenuphar; Albedo Audio Aptica; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V & VI & Submission; German Physiks HRS-120; Eversound Essence; Fram Midi 150 & 120; Acelec Model One; sound|kaos Vox3a [on review]; Aurai Audio M1 [on review]; Sotto Voce Stereo 3 [on review]
Cables: Complete loom of Allnic Audio ZL3000 and Zu Event; KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Black Cat Cable redlevel Lupo; Ocellia OCC Silver; LessLoss C-MARC Entropic process cords between wall and rack upstairs and downstairs
Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps/sub
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands 
Sundry accessories: Acoustic System resonators, LessLoss Firewall for Loudspeakers
Room: 4 x 6m with high gabled beam ceiling opening into 4 x 8m kitchen and 5 x 8m living room, hence no wall behind the listening chairs
Review component retail: €1'100

AC/DC. Even if we didn't do the group's Aussie Rock, we could still use their A for analog, D for digital and two C for converters and make us two hifi components. And today we'd want to. That's because here we deal with a D/D or digital-to-digital converter as only one half of the D-to-A equation. It buffers, reclocks and dejitters inbound binary signal purely in the digital domain. Apply dual/quad upsampling or none. Keep incoming AES/EBU, coax, Toslink in the same format just polished up; or change to another format into the DAC of your choice. Only a USB output is MIA because it wouldn't carry a clock signal.

J-Link III is pin-specific I²S over HDMI to pipe up to 384PCM or DSD256 into the JAVS X7-DAC MQA. It likely won't match I²S pin assignments of non-JAVS DACs. All other digital output formats thus limit to 192kHz as per their industry spec. To listen to anything higher past the X7-DDC, set your own DAC to max upsampling and target resampled 352.8/384, 705.6/768 or even 1'411.2/1'536kHz depending on its capabilities. The DC input takes not just the stock switching power brick but optionally the company's battery/super-cap Clean Power in a matching half-width case. That can power both X7-DDC Femto and X7-DAC MQA for a tidy threesome with squeaky-clean DC like Nagra's Classic PSU does for their range.

I sense your grumble like faint tremors presaging an earthquake.

"Why would I want this thing when my DAC already has all the inputs I need?"

Join the club. For those of us who don't need to supply digital signal to multiple DACs off a single source, it's a very fair question. I don't understand why double clocking in first a DDC then DAC (here with exactly the same femto clocks) has audible benefits. My ears have simply accepted that it does; and whatever else might go on in these reclockers. And yes, given their demonstrable efficacy, I'd much prefer if they were already built into our costly DACs so we wouldn't need extra boxes and cables. But sometimes reality bites. Thus our Denafrips Terminator doesn't jack directly into the iMac's port. Its USB instead runs through a super-cap'd Soundaware D300Ref which outputs it as precision-clocked I²S over HDMI.

It's also why my desktop runs a battery-powered Audiobyte Hydra X1+ to insert between PC and USB DAC. I heard similar benefits with a Mutec USB-3+ under review. Grimm Audio's MU1 includes an ultra-precision sample-rate converter/reclocker in proprietary FPGA code doing a better job of it than commercial on-chip solutions.

As an aside: JAVS have the Romeo and Juliet models which act like a two-step UHF noise blocker for incoming USB signal. "The contaminated USB input signal is first sorted by Romeo's primary femto clock before being converted to an Ethernet signal and transmitted to Juliet. Here it encounters a second clock alignment with battery power before going to your DAC. It's rather complicated but does enable us to minimize the transmission of digital noise to the final DAC via physical isolation."

This is a physical example of multi-stage signal purification from serialized reclocking in multiple components. In current parlance, it might be called a two-box USB isolator and regenerator.

When the JAVS X7-DAC MQA with Clean Power walked off with a well-deserved award [upper right], I was keen to know what today's box might do for it. I also wanted to learn what it could do for other D/A converters. Modularity means bolt-on opportunities. Which means a possibly new lease on life for aged DACs like our 7-year old Auralic. "Don't bin 'em. Revive 'em!" could be the bumper sticker.


Under the clam-shell covers of the X7-DAC MQA and Clean Power. The former's two precision clocks are clearly visible on their own board at the rear panel.

"The X7-DDC Femto is built on asynchronous sample rate converter functionality. This enables high-quality Bluetooth too because those signals also get processed by our upscale femto clock." If we visit the company legacy page, we understand how the number '7' in today's model names reflects their 7th generation. JAVS have refined their tech for years before deciding to go global. They've done their homework to graduate first.

X7-DDC Femto with switching power brick, figure-8 power cord and two precision clocks in the closeup

Where does the €1'100 X7-DDC Femto fall on price? Without Clean Power option, between Denafrips Iris & Gaia so well below Innuos' Phoenix. At €2'250 with outboard PSU, it's still less than the Innuos, a lot less than our €3'600 Soundaware D300Ref, €750 more than the top Denafrips. Korea's unique selling proposition is the 1-2-3 combo of DDC, DAC and PSU. You can do just their DAC, just their DDC with your own DAC, add the Clean Power to either or go gilded trio. Here flexibility is king. It's the Kali Yoga of converterage. I'd stretch to our Denafrips Terminator with latest processor board, COS Engineering D1 and H1, Auralic Vega and, of course, its own X7 stable mate still on hand.

Having already described the Clean Power benefits to the X7-DAC in my first JAVS review, I'd now tap the PSU's second power outlet and spread its luv around.

For an alternate take on the DDC topic which some still find contentious, read about Rajiv Arora's exploits here. For some humorous thoughts on digital transports by John Darko, go here. For my own most current attempt at grading certain tweaks by efficacy, there's this. In today's context, a tweak is anything which you can take out of your system and still have sound. Think racks, footers, subwoofers, super tweeters, black boxes, filters, DDC, AC/DC conditioners, acoustic resonators, cable lifters and more.