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AMP-23R 3rd opinion

Reviewer: Frederic Beudot
Digital Source: Aurender A10 streamer + Denafrips Pontus DAC, LHY SW6 ethernet switch, Jay's Audio CDT2 Mk2
Analog Source: VPI Scout 1.1,  Zu-DL103 MkII, Genesis Phono Gold
Amplifier: Triode Labs 2A3i
Speakers: Ocellia Calliope .21 Twin Signature, Rogers LS 3/5a, Zu Essence
Cables: Zu Varial, Ocellia RCA cables, Zu Event MkII speaker cables
Power cords: Zu Mother, Ocellia power cables, Absolute Fidelity power cables
Powerline conditioning: Isotek Nova
Sundry accessories: Isolpads under electronics, GIK Audio room treatment
Room size: 18'x14'x10'
Review component retail: $6'250

I really had no intentions to get back into the reviewing gig when I emailed Srajan a few weeks ago. I'd just found his commentary on the Tektron 211 SET integrated very relatable because it mirrored my own impressions of the breed. So I simply wrote in to say hello. A few emails later, the idea to pen a follow-up on the Enleum AMP-23R turned into an open invitation to again contribute think pieces and reviews as I continue my musical journey through life. Before I do, let's rewind a few years. After 15 years of contributing to 6moons I had to reluctantly walk away. I was experiencing severe ear pain which affected my ability to enjoy music or form any objective opinion about a piece of gear. Two years and many audiograms later, correct diagnosis and treatments finally in place, my hearing for a fifty-year old is back to normal. The very top of the spectrum escapes me but there was no other permanent damage other than what time itself had done to frequencies above 12kHz. For the past six months I've enjoyed concerts and my system even more than before. Thinking that after four decades surrounded by music, I'd have to live out the rest of my days without it was scary. It certainly put things into perspective and motivated me extra to get my system 'just right'. It's that meandering journey which led me to Srajan's review of the Tektron 211 then reconnecting with my old audio mentor.

For the past decade or so my reference speakers have been Samuel Furon's unusual Ocellia Calliope 21 Silver Signature, the ultimate expression of Bernard Salabert's original 21cm PHY widebander augmented by a pair of piezo tweeters. Those only handle upper harmonics with no filter as their output naturally segues in where the PHY fades out. The cabinet is a complex folded open baffle comprising a heavy and inert front panel to anchor the drivers to whilst the sides and top of the cabinet are made of extremely light wooden sheets to dissipate energy extremely fast. The bottom is open so the material the speaker sits on significantly impacts how it sounds, especially the bass. I find hardwood floors best, short-pile rugs on tiles a close second for depth, speed and bass clarity. The back panel is a door that can be wide open to take full advantage of the folded open baffle design—how I like mine best—but the door can be partially or fully closed to minimize interactions with the front wall for a more direct presentation. To this day the big Calliope remains one of the most unique expressions of the filterless widebander I've come across. It packs the speed, transparency and midrange naturalness you expect from the breed without any of the colorations that plague horns. Bass reach isn't abysmal. Set up properly these will reach into the mid 40s but don't expect chest-pounding impact. The closest I've heard was Cube Audio's Nenuphar which I could happily live with but I do like how the Calliope's open back energizes the whole room rather than the more directional Nenuphar pattern. The trade-off is that the Calliope don't image as sharply and precisely though the dual tweeters of my Signature model do significant improve over the base model. The DeVore Fidelity O93 and O96 offer a very similar set of qualities with slightly less transparency and speed, a more comfortable presentation with a bit more LF body. The Ocellia on the other hand convey the artists' raw energy with less editorializing, a key trait of their performance that we'll revisit when talking amps. Zu speakers can claim the raw energy territory even better but come with some coloration and less transparency even in their latest nano-particle infused driver iterations.

One of our hobby's long-held beliefs, one might even say dogmas, has been that widebanders only work well with SET. If you dig deeper, you'll find a combination of factors contributing to what I now know to be mostly myth. High-efficiency widebanders usually come with high impedances, often 16Ω or up. That's ideal for single-ended triodes which love delivering voltage swings but for the most part are wimps when it comes to pushing current through a load. Triodes mated with high-bandwidth output transformers find high Ω the best environment to shine in whereas solid-state designs, depending on circuit topology, don't always excel under those conditions. The other element that often plays into the perceived lack of compatibility between widebanders and transistors is the latter's higher damping factor, especially from push-pull topologies with negative feedback. Widebanders in general don't have deep and powerful bass so the tighter the control from the amplifier over membrane movement, the sooner they overdamp and attenuate. The worst incompatibility will turn a rich upper bass and midrange into a cold, sterile and lifeless mess. My Ocellia have proven particularly sensitive to that mismatch. Many highly regarded amplifiers came then departed my music room completely dejected. The Ocellia are a bit diva-esque when it comes to partners and will show their displeasure without ambiguity. They've chewed through and spit out solid-state, push-pull tubes even single-ended triodes by the dozen. It's the rare exception that makes these ladies sing. But when they do, they're hard to resist. I doubt you'll be interested in a blow-by-blow account of all those stillborn sessions so let me summarize a decade of experimentation with some broad strokes.

Ocellia recommend their own 300B p/p amplifier as the best partner. Although their custom pure silver output transformers do give their 300B more agility than typical, it remains my least favourite triode. From Yamamoto to Audio Note Meishu, from Trafomatic to Western Electric's 91e integrated, I tried some of the most lauded examples of the breed. Though they all had a beguilingly liquid upper midrange that made singers float in 3D in between the speakers, even the most lit-up 300B XLS designs still blurred transients and turned to mush when dealing with complex signal. If your musical taste solely comprises Bach's violin sonatas, look no further. If you equally enjoy Shostakovich's 11th Symphony let alone Led Zep, prepare for a flattening of dynamics and overall confused imaging that doesn't serve either genre well. The direct-heated 211 offers a slot of similarities to the 300B but its centre of gravity is a bit lower. It excels at the lower rather than upper midrange and the best iterations I heard came from Audio Note UK and Tron. They had more drive and macrodynamic abilities than the 300B but at prices that were eye-watering. It doesn't seem that the Tektron Srajan reviewed bent that trend. The 45 is my favourite DHT for treble and upper midrange glory. I owned Yamamoto's superb A08s for years which could conjure up sopranos in the room better even than the 300B thanks to its more lifelike handling of transients coupled with that lit-from-within feel the best triodes are known for. Yet with power delivery of just around a watt and no deep bass to speak of, the 45 is a very specialized tube better used in bi-amplified very high-efficiency systems.