January
2019

Country of Origin

Switzerland

Classic PSU

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: €11'500 with two outputs, €13'500 with three outputs, required DC/DC cables included

Twin-chassis statement converter.

Time stands still for no one. So Nagra's new HD DAC X improves over the far from ancient original with higher voltage rails and a power supply of 37 regulated lines which combine "ultra-fast silicon carbide rectifier diodes, ultra low-noise voltage regulators and a virtual battery made up of three times as many super capacitors as we use in our HD Preamp. This nets us a rise time of 1'800V/µs on the 28H inductive step-up transformers which perform passive voltage gain and desymmetrize the signal for the 2 x JAN 5963 tube stage."

Of course big X also gets the sophisticated mechanical isolation system which Nagra pioneered for the HD Preamp. Relative to today's assignment however, it's the power supply that has our interest. Huh? A scaled-down but conceptually related version called Classic PSU can be acquired to power non-HD series even vintage Nagra. Think of their phono stages, preamps, CD player/transports and DAC. In fact, the Classic can power up to three separate decks with 12V, simultaneously. The super caps doing that job take up room. That makes for the minus-one over the original MPS at right. That could drive four Nagra components, one of them via standard battery.

I can't be sure but it seems that Vinnie Rossi's groundbreaking LIO platform (passive, active or DHT preamp, headphone amp, integrated amp, phono stage or all of it) was first to vote on ultra/super capacitors not for president but power supply.

Since then other companies have followed. Gryphon use these hi-tech parts for their DAC module. Nagra did so first for the power supply of their tubed HD Preamp to post a colossal 160dB S/NR. Which segues into why one would strap a legacy or current non-HD Nagra to the Classic PSU: noise; or rather, strategic suppression thereof. When it comes to resolution, noise is public enemy #1. Lowering it becomes an instant upgrade, no further signal-path tweaks required. Nagra being Swiss and heavily engineering-driven, the Classic PSU of course is a plug'n'play proposition.

As a very satisfied owner of their Classic Preamp which upgraded the earlier Jazz, I was admittedly extra curious what this next upgrade path might hold. For those who don't yet know, like the UK's Chord, Nagra have decades of experience with advanced switch-mode power supplies. The Jazz still ran an external linear variant. The Classic includes an upgraded switcher in its deeper chassis for even lower noise with higher current. Tubes + SMPS? It's only good Swiss if perhaps not so common sense. Going beyond switch-mode now was teased by those super capacitors for even lower noise.

At Munich HighEnd 2018…

… Nagra's static display had shown off the HD Preamp and its super-capped power supply with the lids off.

In typical Nagra fashion, these chassis maximize available real estate for highest parts density. Emptiness is left to Buddhists, paying for it to less demanding shoppers. As we see, the HD Preamp's power supply is far more than just a bank of ultra caps. It even has twin toroids. What would the Classic PSU have up its aluminium sleeve? More importantly, what would it do for sonics? As a trickle-down affair from the HD Preamp and HD DAC X, the Classic PSU certainly had very serious design DNA in its Swiss jeans.

One of the HD Preamp's many chicaneries are the mechanically clutched dual-mono transformer volume controls. They can be decoupled for balance offsets, then re-clutched to lock in said offset.

… to be continued…