Country of Origin


Eigentakt demonstrator amplifier

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, Qobuz Hifi, Tidal Hifi, COS Engineering D1, Denafrips Terminator, Soundaware D300Ref, Jay's Audio DAC2-SE & CDP-2 MkII
Preamplifier: Nagra Classic, Wyred4Sound STP-SE Stage II, COS Engineering D1, Vinnie Rossi LIO (AVT module)
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1 monos, SIT-3, F5, F6, F7; Crayon Audio CFA-1.2; Goldmund/Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics NC500 monos; LinnenberG Audio Liszt monos
Loudspeakers: Audio Physic Codex; Cube Audio Nenuphar; Kroma Audio Mimí; Albedo Audio Aptica; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V, VI & Submission; German Physiks HRS-120; Eversound Essence; Fram Midi 150
Cables: Complete loom of Allnic Audio ZL 3000/5000; 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 [on loan]
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

German Wima and Japanese Rubycon capacitors fulfill audiophile pedigree.

Hello Dolly.

Actually, that's not what the emailer said. Instead, "you might have picked up some noises about me taking part in a new Danish project called Purifi. We combine work on class D amplifiers and speaker drive units specifically to reduce distortion in both. My partner Lars Risbo and I have achieved a roughly 20dB improvement over current designs in both cases. Sonically the impact is quite startling. We are gearing up to become an OEM supplier of drive units and amplifiers. A few key customers have already gotten samples to play with. So we decided it's time to go a bit more public." That was Bruno Putzeys, inventor of class D uCD/Ncore, collaborator in Grimm Audio, engineer with Kii Audio.

Behind Purifi, there's the already mentioned Lars Risbo who founded Toccata Technology which was later acquired by Texas Instuments for its PCM-PWM direct-digital technology. Lars holds more than 30 US patent families. There's Carsten Tinggaard, founder/owner of PointSource Acoustics, previous product manager at Danish Sound Technology and CTO of Tymphany where he was in charge of establishing the Danish R&D facility which worked on Peerless, Vifa and ScanSpeak drivers. There's Peter Lyngdorf of Hi Fi Klubben, Dali and Steinway Lyngdorf, a group with 1000+ employees and multiple factories in Denmark and China. Peter's background includes stints at NAD, Snell and TacT Audio. There's Claus Neesgaard who worked for Texas Instruments, Kim Madsen who also came from there plus developed military power modules for Alcatel's Ariane 5 Rocket and several Dynatech fighter jets. Finally there's Søren Poulsen again from TI where he owns definition and architecture development of the world's highest-power top-performing IC amplifier with 5 US patents. That's an amazing dream team with fantastic resources.

Purifi's first amplifier invention is the 1ET400A mono module. It delivers more than 400w/4Ω with 131dB(A) dynamic range, 12.8dB of gain, THD+N below 0.00017% and output noise of 11.5μV(A) with sub 50μΩ output impedance. The high 75dB+ loop gain across the audio band "corresponds to an unprecedented 110MHz gain bandwidth" with "negligible intermodulation distortion, extremely low THD at any frequency and power level right until clipping", with a "high power supply rejection ratio" where "even a simple off-the-shelf unregulated SMPS won't degrade audio performance, load-invariant frequency response", 60kHz flat bandwidth with a second order low-pass and more.

"Presumably this new class D tech will position itself above Ncore 1200 but remain a separate entity under Purifi rather than Hypex?" was my obvious question. At right we see Mola Mola's Kaluga monos as Bruno's own take on NC1200 boards adopted also by brands like Bel Canto Black and Nord Acoustics. Bruno: "Hypex and I separated amicably a while ago so they're not involved in any of the new work. Measured and sonically, the Eigentakt circuit is quite a step up in performance from Ncore. So we're indeed looking to establish it as the new high-end standard. Purifi is actually three entities – one that does fundamental research into both loudspeaker driver units and amplifiers, then two subsidiaries to commercialize drivers and amplifiers respectively.

"As you can imagine, we've been in early discussions with the usual suspects and response is pretty consistent, namely that they wouldn't re-engineer existing products but be happy to switch for new products. That sounds entirely reasonable. Actually more difficult is the product tier just below the top end. There a common response is "well, Ncore modules are available from stock and they're good enough, why take risks?" Either way, for a while we'll have to toot our own horn first by getting the right people to hear the modules in their evaluation kit, then report on what they heard. In the case of Ncore I recall that the only media outlet prepared to do a review of the evaluation kit was 6moons. Everyone else had a strict policy of reviewing only products in a form that end users can buy. Would you still be up for a review of a lab-grade demo?"

Hello Dolly. "Great! As soon as we can spare a demo unit, we'll make arrangements."