Collusion. "I'm not even sure that's a crime." (Rudy Giuliani on the Trump election's Russian interference angle.) Today's review is about collusion of a different sort. Had you been hacking my email account, you'd have read that "I have an idea/proposal for a review I'd like to do - your 300B monos. I very recently reviewed an exceptional pair of speakers made in Poland. They use their own 10" widebander with triple whizzer and 2.4 Tesla neodymium motor with 81 magnet slugs and a very unusual phenolic spider. Though 'only' 93dB sensitive, they behave exactly like 100dB types. By that I mean, they really prefer high output impedance to generate an old-fashioned ratio between output and input impedance. I had an amp of 0.25Ω which still was very good. By the time I got to a damping factor of 100, things started to overdamp. Once I hit 0.00x output impedances, things got very bright and a good octave of bass just disappeared. In short, this is the perfect type speaker to show off the special virtues of low-power no-feedback triode amps. It's not so insanely efficient as to sniff out the most subliminal noise. Unlike most 100dB types, it's got real bandwidth to 30Hz! I reviewed it with transistor amps which have 4Ω output impedance (single stage, single-ended, no feedback, static induction transistor types) and the results were stunning. I've owned a few valve amps over the years like Art Audio, Octave, Yamamoto and Trafomatic. But when I no longer had speakers which play to and not against them, I divested myself of these amps. Now I'm back in this sector. If you are interested, let's talk." The email recipient was Reinhard Thöress, owner of the eponymous valve audio firm in Germany.


Monitoring my account, you'd have been privy to his response a day later. "Amazing FR drivers those guys from Poland make. Phenolic spider, hybrid magnet, underhung(!) voice coil. Whoa. I am not a FR person myself. Never was, actually. That's despite the fact that years ago I created the FR20MkII based on a rather unique principle which one might call 'one-way speakers with three voice coils'. It had a 12" woofer in series with the 8" FR driver where the coil inductance of the 12er was used to form a LCR correction network to flatten the FR's response. I also had an indirectly radiating (140x60°!) super tweeter to compensate for the treble directivity of the FR.

"However... perhaps my freshly minted single-ended-triode/single-ended Mosfet EHT monos (EHT = Eintakt Hybrid Triode in German) would be an even better choice despite their moderate 0.5Ω impedance? This would combine particular loudspeakers with particular electronics. These monos feature an input attenuator switch (low, mid, high, full gain/sensitivity) implemented such as to allow for minimalist 'tone controls' by adding just one part per channel. We could share insights and create two or three tone registers for these new FR floorstanders. As it is conceptually forbidden to equalize the response between amp and FR driver, we do this at the input of the amp by adding just one part. This avoids clumsy sound-deteriorating compensation circuitry. You take your pen and make a thrilling review out of all that, creating something unusual and different in the process. Would that be an option?"


Perusing Reinhard's PDF, I learnt that his EHT were zero feedback pure class A point-to-point wired 40W/6Ω designs. Unusually, they were "fully short-circuit proof at the outputs without any sound-degrading protection. Moreover, a switch-on delay too is omitted because switching on/off develops no disturbing noise or dangerous signal in this circuit." It consists of a single-ended triode gain stage followed by a unity-gain Mosfet buffer. "This fully exploits and mates the most desirable characteristics of tubes and transistors as determined by their very natures. In spite of its obvious advantages, elegance and extremely high sonic capability, the EHT concept has never before been commercialized in serial audio production as far as we know. This is likely due to its low efficiency and rather tricky implementation. Yet analysis easily shows this topology to represent the purest form of all possible single-ended triode power amp configurations. Specifically it shows that without compromising sound quality, the EHT more easily obtains higher output power and with lower distortion than does all-tube single-ended triode amplification. That's because the critical power-tube-driven step-down output transformer as the typical all-tube impedance matching output arrangement can be omitted. As a result, the voltage swing required from the driver stage is up to 10 x lower (!) for an EHT of equivalent power. This crucial insight was the basis for our pursuit of this hybrid concept." The double-coil ultra low-noise C-core power transformers Reinhard winds in-house to be available at the EU's 230VAC, then at 100VAC (Japan), 220VAC (South Korea, Thailand, Russia, mainland China) and 245VAC (Australia). Weighing 24kg, each amp measures 15.4 x 43.4 x 43.4cm. [Reinhard's photo from Dawid Grzyb's review of his F2A11.]