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Reviewer: Marja & Henk
Financial Interests: click here
Sources: CEC TL5100, Audio Note tube DAC; Philips DVP 5500S SACD/DVD player
Preamp/integrated: TacT RCS 2.0 room control system, modified Audio Note Meishu with WE 300B (or AVVT, JJ, KR Audio 300B output tubes); Moscode HR401; Trends Audio TA-10; Avantgarde Acoustic Model Three [in for review] ; Qables iQube [in for review];
Speakers: Avantgarde Acoustic Duo Omega; Avantgarde Acoustic Solo in HT 2.0 setting; Podium Sound Model 1 [in for review]
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. Nanotech Golden Strada #79 nano 3; Nanotech Golden Strada #79; Qables Silver Cab and Gold Cab [in for review]
Power line conditioning: Omtec PowerControllers; PS Audio P1000
Equipment racks: Two double sets of Solid Tech Radius; Acoustic System amplifier shelf
Sundry accessories: IAR carbon CD damper; Boston Audio graphite CD damper, Denson demagnetizer CD; Furutech DeMag; Nanotech Nespa #1; Machina Dynamica Magic Box; TacT RCS calibrated microphone and software; Exact Audio Copy software; Compaq server w/Windows Server 2003 and XP; iPod; wood, brass and aluminum cones and pyramids; Xitel surround processor; Manley Skipjack; Boston Audio Design TuneBlocks
Room treatment: Acoustic System International; Gizmo's Harley Davidson cap
Review component retail: €399

Roughly midway in the last century when Henk hadn't yet started growing his beard because that work was too hard for a toddler, he had a very interesting neighbor. Mr. Neighbor not only had one of the first cars on the block, a true Glas Isaria Goggomobil, but also worked for the Svenska Kugellegar Fabriken or SKF ball bearing factory. Now and then this neighbor made a present in the form of a bearing ball which, at least compared to the size of Henk's hands at that time, seemed quite large. In his little hands the initially cold and very heavy steel ball would warm up to give a feeling of comfort. Ever since, small, smooth and relatively heavy things do remind him of those carefree days.
Such a nostalgic feeling presented itself as well when we received the iQube portable amplifier for review. The iQube concept was
birthed by Dutch audio distributor Hans Oosterwaal. He wanted a high quality, ultra efficient amplifier to use with a headphone in conjunction with a portable music player. Hence the amplifier should be portable as well. Anecdotally, Hans did not want to be excluded from the rest of the family as they watched sports on TV while Hans was listening to music. He liked to be in the family room with them and still enjoy his music.

Hans had previously worked at Philips so it was natural that he contacted two other ex-Philips employees, Bruno Putzeys and Guido Tent. After their own Philips years, these two are now both very successful in their own audio industry ventures. Bruno is designing circuits and filters at Hypex and Guido runs Tent Labs known for its components and DIY CD player. Together they also form one half of Grimm Audio, a company that caters to the professional recording industry with high-end products.
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Hans presented his two engineers with a 4-point wish list for his project. Along the way, the project was baptized iQube, a very apt nomenclature. The four points to be incorporated were sound, design, portability and battery power. Sound was most important and the central focus of the project. Once finished, the product had to have a strictly neutral character and should be as transparent as possible. From an external design standpoint, the iQube was to have a high me-too factor. Just like Apple's classy design team proved how a well conceived exterior not necessarily based on the form follows function credo can be responsible for the success of a product, the iQube was to have a timeless and almost classic look. For portability, the maximum allowable size was that of the largest iPod with which it had to integrate well to determine the location of the controls and connectors. While traveling, the iQube could not be burdensome and thus had to be easy to carry and store. The power supply of the iQube was to run off standard alkaline batteries with an extended operational time (alkaline batteries are widely available and most brands are safe and affordable). Rechargeable batteries had to be copasetic and recharge simply. Finally, the iQube had to accept signals from the line output of a (portable) music player or its headphone output.


This wish list was not simple to comply with as one vital aspect not yet mentioned was pricing. One can design a wonderful portable amplifier but when production costs go off the reservation, it's worthless. Against this background, Hans, Bruno and Guido went to work. Early in the design stage it became clear that the iQube would have a Class D amplifier heart not just because class D maven Bruno was on board but because class D has many advantages for portable use. From the battery part of the wish list, the figure of 70 hours was targeted for battery lifetime and class D's power efficiency of up to 95% insured that this design goal could be met. With Hans also wanting something unique, the use of a class D portable module left room for Guido's desire to add at least one exceptional application of special techniques to any design he works on.


Class D is quite mature by now but a few items need to be crossed off for best sound. One of these is adequate filtering. Guido explained that the iQube amplifier runs at a 500kHz carrier switching frequency filtered by an 80kHz second order low-pass filter which also determines the amplifier's bandwidth. Post filtering, a very small percentage of ultrasonics remains but the induction of a headphone at 500kHz is so high as to eliminate any energy generation.