Tubes done different

Linear Tube Audio. Kora. Alieno. Today is about three brands whose designers approach tube amplification other than the vast majority. To eliminate the classic output transformer, Berning and their US licensee LTA upshift the music signal onto a high-frequency carrier wave like a radio signal. This so-called ZOTL circuit then applies minuscule RF transformers to step down the tube-amplified signal from the carrier wave before presenting it at the speaker terminals. Having heard Berning amps and later reviewed a few LTA versions, they clearly did not sound like traditional transformer-coupled brethren. Kora of France cluster four small-signal triodes for voltage gain in their 2 x 250V Square Tube block followed by what most armchair engineers should probably refer to as a transistor current buffer with a gain of less than one. Alas, our French engineers are adamant. Theirs is not a classic hybrid circuit they say. It works and sounds like a pure tube amp just with more power. Past the Munich show and following up on a reader's recommendation who just took on Kora distribution for New Zealand, I'll try to secure a review sample to clap ears on their difference. Coming from Italy, even more outré reads Alieno's claim that their 100LTD 2A3 no-feedback SET with 1MHz internal bandwidth outputting 100wpc/3Ω at 55A max has no transistors in the signal path at all, just in the power supply. That just flies right over my head to leave my hair in a sorry mess. What hair you ask? My point precisely. But with these three unique approaches to thermionic gain claimed not to be traditional hybrids, today's curious shopper clearly has interesting options to explore. The tech details of these executions are far beyond my paygrade. This mini feature isn't about that. It's merely to direct your attention at what look to be exciting options in the outer left field of valve amplification. You take it from there…