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Differently wrinkled. On both sides of the tube/transistor fence, designers may look across for inspiration. So Jarek Waszczyszyn of Ancient Audio currently works on a classic 300B SET with custom switching power [below]. EveAnna Manley years back commissioned Bruno Putzeys for an SMPS for her small-signal valve gear. Nagra have used their own for even longer. Mark O'Brien of Rogue Audio does big valve amps but also embeds small triodes in the feedback loop of class D outputs. Designers like Jean Hiraga who consider a circuit's harmonic distortion behavior under dynamic conditions relative to how the human brain processes it include the late Eduardo de Lima of Audiopax, Vladimir Shushurin of Lamm, Luca Chiomenti of Riviera Audio Labs and Michael Vanden Broeck of Tenor Audio. In this group, designers may work in all tube, hybrid or pure transistor circuits. Within their catalogues, they achieve virtually identical results regardless. Reinhard Thöress works in pure tubes but also applies the same circuit concept to simple 2-stage hybrids, again for matching sonics but with superior current drive.
Others look at the high voltage ratios whereby triodes amplify gain to apply the same idea to transistors. These include Cees Ruijtenberg of Metrum/Sonnet who invokes deliberate triode cloning; and T+A's high-voltage range. spl too run their transistors on unusually high voltages to increase dynamic range. Some designers instead focus on classic tube output transformers to capture their effect in solid state. One such is Massimiliano Magri of Grandinote. McIntosh do it with autoformers. In the hybrid sector, Mario CanEver mixes up small triodes, output transistors, interstage and output transformers. In the pure valve sector, David Berning and his Linear Tube Audio licensee regard the classic output transformer as limited. To transcend it, they replace it with puny RF transformers of very different turns ratios to demodulate their audio signal which rides on a high-frequency carrier wave. S.P.E.C. of Japan model their class D circuits on classic valve circuits and sonics. Nelson Pass has groomed certain transistors for classic triode behavior, even eliminated ubiquitous degeneration resistors.
And who in this context could forget the classic Bob Carver challenge which focused on an amp's transfer function by claiming that if it could be duplicated by another amp, that amp would sound identical regardless of cost? To conclude our little detour, many smart people have looked into classic valve circuits to wonder what makes them tick: simplicity from fewer gain stages so far simpler if also far higher THD? Magnetic coupling? No global or local feedback? High output Ω? High bias voltages? Other? Considering how Guido Tent collaborated with Bruno Putzeys during their earlier joint Grimm Audio period, it's perhaps unsurprising that for a valve circuit, the Trans-SE10 thinks different on negative feedback. Arguably nobody in recent hifi has been more outspoken about the proper use of high feedback than Putzeys. It's a counter position to the 'no feedback' trend but given the many Hypex, nCore and already Purifi amps plus Mola Mola, it's certainly no less popular or commercially successful. As a result of all this gazing across the fence, many feel that traditional tube/transistor lines have blurred. This transcends gain devices. It includes operational classes. Tubes can sound like transistors and vice versa, class D like class A. It's when one aks what tubes or transistors or class A and D sound like per se that things collapse. Was it ever neatly fixed? It's probably been fluid all along even if, during certain time periods, default flavors associated with each by pure majority. But who can say how far back exceptions existed even if only as one-up efforts?
The more we listen to different things over time, the more foolhardy it seems to pin fixed sonic expectations on any circuit type or output device. Any proof finds itself quickly challenged by exceptions. How many exceptions does it take to undermine solid classifications in the first place? It makes a good intro for today's review when the circuit descriptions of the Trans-SE10 could suggest that this tube amp will sound like class D. It's got loads of negative feedback. Surely that settles it? Even if there were parallels, which class D do we mean? AGD/Merrill types? nCore/Purifi? ICEpower as massaged by E.J. Sarmento of Wyred4Sound? Pascal as tweaked by Aavik's Michael Børresen? Powersoft as groomed by Sven Boenicke [above]? You see the point. Neat stereotyping no longer works.
It probably never did. In reviews, it's simply quicker and easier than describing what something sounds like without type casting with the elevator pitch: "Think Mola-Mola meets Yamamoto." Can you see that movie in your head?
Not. So let's find out whether I manage any better today.
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