Country of Origin
Reviewer: Marja & Henk
Financial Interests: click here
Sources: PS Audio PWT; Dr. Feickert Blackbird MKII/DFA 1o5/Zu DL-103; Takumi TT Level 2.1 [in for review]; Holbo Air Bearing Turntable System [in for review]
DAC: Mytek Brooklyn; T+A DAC8 [loaner]
Streaming sources: Devialet AIR; La Rosita Beta; Qobuz Desktop, Tidal Desktop; Sound Galleries SGM 2015 [loaner]; Mytek Brooklyn Bridge [in for review]'
Preamp/integrated/power: Audio Note Meishu with WE 300B (or AVVT, JJ, KR Audio 300B output tubes); dual Devialet D-Premier; PTP Audio Blok 20; Hypex Ncore 1200 based monoblocks; Trafomatic Kaivalya; Trafomatic Reference One; Trafomatic Reference Phono One; Music First Passive Magnetic; Gold Note PH-10 phono pre amp with PSU-10 external power supply [in for review]; SPEC RPA-MG1000 [in for review]
Speakers: Avantgarde Acoustic Duo Omega; Arcadian Audio Pnoe; Podium Sound One; WLM Sub 12; Sounddeco Alpha F3; dual Zu Submisson MKI; Soltanus Virtuoso ESL; Audio Alto AA LA17 [in for review]
Cables: complete loom of ASI LiveLine cables; full loom of Crystal Cable cables; full loom of Nanotec Golden Strada; Audiomica Pearl Consequence interconnect; Audiomica Pebble Consequence
Power line conditioning: PS Audio Powerplant Premier; PS Audio Humbuster III; IsoTek Evo 3 Syncro; AudioMica Allbit Consequence
Equipment racks: Solid Tech and ASI amplifier and TT shelf
Indispensable accessories: Furutech DeMag; ClearAudio Double Matrix; Franc Audio Ceramic Disc Classic; Shakti Stones; Kemp polarity checker; Akiko Audio Corelli,Costello and Phono Booster; Pink Faun LAN Isolator
Online music purveyors: qobuz.com, tidal.com, bandcamp.com, amazon.co.uk
Room treatment: Acoustic System International resonators, sugar cubes, diffusers
Room size: ca. 14.5 x 7.5m with a ceiling height of 3.5m, brick walls, wooden flooring upstairs | ca 7 x 5m with a ceiling height of 3.5m, brick walls and concrete floor downstairs
Price of review item: €189/1m
From our review of Audiocadabra's Optimus dual-headed USB cable, we quote: "Once the USB connection is made and our computer running audio streaming software communicates with our USB DAC, the fun begins. When all is perfect, the resultant tunes will be devoid of any drop-outs or crackles yet full of dynamics. Transients kick with impact and the soundstage has plenty of depth and all of that comes across at modest to low volumes. Yes, that would be nice and actually the case; in an ideal world. Unfortunately, ours isn't (yet) and more often than not, the perceived sound is noisy, lacks punch and dynamic contrast. A gray veil covers the musical landscape and with prolonged listening, neck pain and headaches are your reward. The cause? Mainly jitter.
"The signal which your computer sends to the DAC is intended as nicely sharp-edged square waves like in the example above. Alas, nature doesn't know square waves, only sine waves. To create that square wave upon which our digital transmissions rely, the computer must overlap several sine waves – or more precisely, superimpose several odd harmonics onto a Fourier square wave. That nicely composed square wave now runs down the USB cable between computer and DAC. The USB 2.0 standard for the cable demands up to 480Mb of data density per second and states that the cable should comply with a 90Ω impedance. In addition, the data signal aka those proverbial just 1s and 0s are represented by a +200mV difference between the D+/D- signals for a 1; and a -200mV difference for a 0. The standard USB cable has 4 leads: a power lead that carries 5V from the source to the connected equipment, two data leads (the aforementioned D+ and D-) and signal ground."
Originally USB was to supersede the IT domain's serial and parallel interfaces. However, soon the very practical universal interface found itself adopted elsewhere including home audio. The four conductor leads form two pairs. Two twisted data wires carry the signal, two supply wires handle 5V and ground. For the twisted pair, the USB standard requires 28-gauge copper while the supply wires can be 20-28 gauge. That number indicates the diameter of the round conductor (the higher the number, the thinner the wire). By twisting two data wires, there is a resultant differential mode impedance of 90Ω against ground. Next, the USB specification demands an aluminum shield followed by a copper shielding braid that covers at least 65% of the cables' surface. Finally an outer PVC sleeve finishes the build. Of course the specification committee had the best intentions to guarantee flawless signal conduit from point A to point B. In practice, there are many non-compliant USB cables on the market. Cheap conductor material, no copper braid or just a single-sided evaporation of aluminum onto a foil all lower costs. For pure IT use, these cables might get away with it as the application which the USB connection there is part of will have some type of error correction. In audio however, there is no such error correction. Data sent from source to DAC happens in real time. If part of the signal is damaged or missing, the DAC must cover things up. When unsuccessful, you will hear drop-outs or other forms of distortion.
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