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STI-500 V2

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, Fore Audio DAISy1, COS Engineering D1, Denafrips Terminator, Soundaware D300Ref,  AURALiC Vega 
Preamplifier: Nagra Classic, Wyred4Sound STP-SE Stage II, Vinnie Rossi LIO (AVT module)
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1 monos, 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
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
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
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 in US: $2'499/2'999 for 500/1000 models

STI. V2. Series. Spelled out, that becomes Stereo Integrated, Version 2, two power options. By using similarly sized B&O ICEpower® ASX2 mono modules, a customer can pick 250/430wpc into 8/4Ω for the STI-500; or 460/725wpc into 8/4Ω for the 1000.

More choices present for chassis trim—black or anthracite gray—and standard terminals plus standard internal OFC hookup wiring vs upgraded Kimber TCX cabling with WBT nextgen® binding posts. Either way there's a vacuum fluorescent readout to display active input and volume for the analog resistor ladder which is triggered by the optical encoder volume/power knob. There's a differential signal path which converts all 4 RCA inputs to balanced.

There's one XLR input and one 100Ω RCA output, to a subwoofer perhaps. Any input can be configured for volume bypass aka AV thru-put. There's high 42dB voltage gain and high dynamic range of 111dB/108dB for the 500/1000 versions. There's low idle noise of sub 125µV/215µV. At ±0.1dB/0.15dB, 20kHz bandwidth for class D is high again whilst 0.005Ω output impedance is a modern low to give a high 2'000 damping factor for better woofer control.

The same low/high connection figures for power draw vs power output. We already know that the output watts are high. Even so, idle draw is just 25/35 watts. That's very little for a lot. It's why class D—which is just the letter after C, not shorthand for digital—is considered green tech. It's the most power-efficient gain topology we currently have. It's what drives smart phones, tablets, computers and televisions to benefit from R&D at a massive industrial level far from the hobbyist, boutique or garage-type audio playground.

That this tech is suitable for high-performance audio and not just subwoofer or car-audio sport has been status quo for years. In the high-end sector, pricing for the most ambitious class D amps now pushes $36'000 for a pair of Merrill Audio Element 118 monos with their faster-switching gallium nitride transistors. Which, calm yourself, is not the sandbox Wyred4Sound's EJ Sarmento plays in. The STI-500 in standard trim sets you back $2'500. A 2018 Black Friday Special direct from the factory called it $1'999. Just $500 more nearly doubles power for a 1000 instead. For such coin, cosmetic chrome chicanery with gold-plated accoutrements goes out the window straight into the dump. Katchinnnng. Ka-clunk. It's why their website invokes "rugged construction". Canadian contributor Glen Wagenknecht found much to like when he gave the original STI-1000 a whirl. Except that was nine years ago to the month.

In fast-running hifi time, that's a near century. Investigating the second coming of V2 was thus overdue and Sarmento gracefully proved game. In my book, he's one of the most gifted designers working with stock ICEpower modules. Sonic distinction—voicing—gets built in with custom input buffers. Anyone charging a lot more for class D than Wyred really ought to offer unique/proprietary circuitry. And such brands exist. Others meanwhile are happy to repackage the same modules into shiny chassis with a concomitant bill. Now I prefer a plainer look and the plainer invoice.