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This is the 13th in a series of reviews dedicated to the concept of 32Ohm Audio as embodied by the store of that name in downtown Portland/Oregon and described here - Ed.

Reviewers: Marja & Henk
Financial Interests: click here
Sources: CEC TL5100, Audio Note tube DAC; Philips DVP 5500S SACD/DVD player; iPod Video; Thorens TD 160; Thorens TD124
Preamp/integrated: modified Audio Note Meishu with WE 300B (or AVVT, JJ, KR Audio 300B output tubes); Tri TRV EQ3SE phonostage; Trends Audio TA-10; Qables iQube; NuForce Icon Mobile; RSA Predator; KingRex T20U and Slap; Yarland FV 34 CIIISA
Speakers: Avantgarde Acoustic Duo Omega; Avantgarde Acoustic Solo in HT 2.0 setting; Podium Sound Podium 1 [on loan]
Cables: Audio Note AN/Vx interconnects; Siltech Paris interconnects; Gizmo silver interconnect; Qunex 75 reference interconnect; Crystal Cable CrystalConnect Reference interconnect, CrystalDigit S/PDIF RCA/RCA and RCA/BNC, Y-cable, Crystal Cable Piccolo iPod to XLR, CrystalPower Reference AC-Eur/IEC CrystalSpeak Reference; Audio Note AN-L; Gizmo silver LS cable. Nanotec Golden Strada #79 nano 3; Nanotec Golden Strada #79; Nanotec Golden Strada #201 nano3; full ASI LiveLine set; LessLoss DFPC [in for review]
Power line conditioning:  LessLoss Firewall [in for review]
Equipment racks: Two double sets of Solid Tech Radius; Acoustic System amplifier shelves
Sundry accessories: IAR carbon CD damper; Boston Audio graphite CD damper, Denson demagnetizer CD; Furutech DeMag; Nanotec Nespa #1; Machina Dynamica Magic Box; Exact Audio Copy software; Compaq server w/Windows Server 2008 and XP; ; wood, brass and aluminum cones and pyramids; Manley Skipjack; Boston Audio Design TuneBlocks; ASI TopLine
Room treatment: Full apartment treatment by ASI  with Acoustic System Resonators and Sugar Cubes; Gizmo's Harley Davidson cap
Room size: ca. 8.0 x 4.70m with open extension to a 2.20 x 2.40m A/V bay and open kitchen. Ceiling height is 2.50m, reinforced concrete walls of 45cm, reinforced concrete floors and roof of 30cm. Room has on one side a large glass bay.
Review component retail: €499

March of last year we published our review of the Qables iQube. A good year and a half later now, we can publish a review on their next model, the iQube V2. Just as the older model now christened V1 by default, the new portable headphone amplifier is the result of an intense collaboration between Qables owner Hans Oosterwaal and Guido Tent of Tentlabs. We received a test version that was technically identical to formal production save for a USB connector that was not yet in the correct location betwixt input and output sockets on the back.

While unpacking, we noticed two differences with the previous model at once. The new unit is larger yet seemingly lighter. Where the V1 had Henk flash on childhood memories of handling small but heavy things, the iQube V2 conjured up no such associations.

It measures 12 x 7 x 2.3cm DxWxH while the V1 was 10 x 6 x 2.3cm. Including batteries, the V2 throws 218 grams on the scale, the V1 a mere 6 grams less. The illusion of the V2’s greater lightness is due to it packing 29% more volume. Why was that necessary? The V2 adds a built-in USB DAC.

Think DAC and Guido Tent and arrive at top-class jitter reduction as many Tentlabs products have already proven. His X02 and XO3 clock modules have found their way into many CD players and DACs as either upgrades or stock trim.

However, their mounting size of 45 x 75 x 14mm and 35g mass for a clock assembly were not exactly suitable for a portable device. Guido had to author a more compact solution. So he did.

Though the V2 amplifier is identical to the V1, the oscillator now runs at a frequency derived from the main clock. That still ticks at 12MHz but the oscillator steps down to 375kHz whereas the V1 ran a 500kHz carrier switching frequency off its own clock. The added USB receiver is a PCM2706 slaved to the 12MHz main clock. Within the PCM2706, a phase-locked loop sends output data in native I²S to the SRC4190 sample rate converter which adjusts the incoming sample rate—be it 32, 44.1 or 48 kHz—to a fixed rate suitable to the main clock’s 12MHz frequency.

Guido designed the main clock as an ultra-low jitter device and added a small discrete low-noise power supply for his portable version. Behind the sample rate converter sits the Crystal CS4344 DAC chip. To optimize jitter reduction, the DAC chip derives its clock information directly from the master clock. Handling the clock information in this way while embedding a sample rate converter in the circuit leads to extreme low jitter which naturally improves the overall sound quality.