Condemned traditions. "The 6J5GT is a very old indirectly heated triode. It belongs to what I call the xSN7 family which includes the 6SN7GT, 12SNGT, 6J5, 6J5GT, 12J5, 7N7GT etc. It is characterized as being one half of a 6SN7GT double triode. These all-purpose medium-mu triodes with a gain factor of 20, transconductance of 2.5mA/V and internal resistance of 7'200Ω were designed during times when space and energy savings were not any consideration. For example, a 6SN7GT consumes 6.3V x 0.6A = 3.8 watts of heating power. That's twice what a more 'modern' ECC82 double triode runs which itself is a kind of miniaturized 6SN7GT with almost the same characteristics. But it is exactly this "wasteful" energy consumption which gives it a generous emission from a large cathode. And that leads to the exceptional linearity of the xSN7 family of triodes. It's a fact generally accepted amongst experts and has been frequently confirmed by measurements. For instance, see the book Valve Amplifiers by Morgan Jones, just to mention one good reference. It's not just a bit more linear than other medium-mu triodes. The difference is drastic. So it is no wonder that the tubes of the xSN7 family were heavily employed for high-fidelity audio amplification in the early times of audio. As someone on a mission to explore the very limits of sonics, I'm condemned to follow this tradition." In the EHT monos, this tube is the voltage gain stage.
.aiff files on iMac via Audirvana 3; Soundaware D300Ref USB bridge; Denafrips Terminator (I²S over HDMI); Nagra Classic Preamp; Thöress EHT; Cube Nenuphar; Allnic ZL3000 /5000 cable loom; Vibex AC/DC conditioning
"By contrast, the 12HG7 is a very modern frame-grid pentode specifically designed for video output amplifier services in color TV receivers. I of course employ it in triode mode. Again this is a tube with a very large cathode for high linearity. It's high mu (40 in triode), very high transconductance (larger than 30mA/V) and very low internal resistance when operated as a triode. By simultaneously offering high transconductance and high mu, it becomes the perfect driver/buffer. Image quality of TV receivers was vastly dependent on tube linearity. It is easy to see why the designers of the 12HG7 really had no choice but optimize its linearity to the utmost. After all, early color TV receivers were considered a benchmark of technical progress in electronic engineering at the time. Therefore I employ this tube in my EHT monos and also in my dual-function preamplifier. Just how I use it in the EHT monos makes for the ultimate unity-gain buffer between 6J5GT and the single-ended Mosfet speaker driver."
Having seen two Mosfets, I suspected parallel operation. "Not. Neither do they operate in push/pull mode. Beware: one Mosfet operates as source follower while the other serves as an active load in parallel to the speaker load. That's true single-ended design!"
"If blood will flow when flesh and steel are one, drying in the colour of the evening sun, tomorrow's rain will wash the stains away but something in our minds will always stay.
"Perhaps this final act was meant to clinch a lifetime's argument, that nothing comes from violence and nothing ever could?
"For all those born beneath an angry star lest we forget how fragile we are… on and on the rain will fall like tears from a star, like tears from a star. On and on the rain will say how fragile we are…"
These lyrics are from Sting’s most famous ballad. With them we'll pierce the heart of this Thöress sound.
Anyone exposed to the tacit nearness of death like a car accident, life-threatening illness, high-risk surgery, violent attack or standing at a cliff's edge… they all know it. During these moments, our perception of being alive can flare up. When it mysteriously does, its sudden intensity isn't built on any certainty, strength, conviction or power. It just trembles in tremendous fragility. Yet it's not a condition of weakness or capitulation. It's simple awareness. How thin this veil which separates us from the otherness of death. It's not a mental invocation. Today is a good day to die. Let's be in the moment. Not that. It's an actual feeling awareness. Our bodily presence could be snuffed out. Now. Just like that. It's a live-wire recognition.
It has us insecure. Vulnerable. Cracked open. Exposed. Fragile. Intensely alive. Somehow we inquire through that veil suddenly so transparent. We sense the constant presence of unembodied stillness in which we are not. It's right behind and around our material world. Usually that can seem so solid and secure. Now it doesn't. The butterfly probes gently. Soon the dew drop will shatter and be no more. But right now, it's simply splendid in that precarious balance. Radiant. Alive.
That was the sound of the EHT/Nenuphar combination. Breaking my poetic attempt down into the usual audiophile nuts and bolts, on linearity and resolution, the Thöress monos were essentially on par with our SIT-1 monos even though their 30-60Hz coverage eclipsed the pure less powerful transistors with slightly better damping. On textural sophistication, the Thöress top end was the even more open. On high peaks especially, challenging female vocals powered right through the danger zone without skewing a thing. By contrast, the static induction transistors compressed, narrowed and hardened slightly. The EHT expanded instead without any clenching whatsoever. Those differences were clearly audible but not yet key.
Key was that strange intensity born of vulnerability not dominance. It wasn't the peak-health halo of a top athlete with its charismatic shine which in audio terms becomes vitality and gloss. It wasn't about raw physical strength which hifi translates into a sound that presents authoritatively and powerfully. This sound wasn't about vise-grip control. Not that control lacked. Far from it. It simply wasn't under consideration. When perfectly sated after a good meal, looking at food on a super market haul doesn't talk to us like it does when we're hungry. It's not about food per se. It's about our state and how that changes how we relate. In musical terms, power and control were magnificently present but as such, didn't talk to me. What did was unusual liquidity and expressiveness combined with a peculiar sense of something having cracked wide open. Whilst I appreciate how 'non-objective' or fluffy that reads, it's actually my best shot. It really does resonate with the actual experience. I'd call the EHT/Nenuphar showing a prime example of mature direct-heated triode sound—single-ended, no feedback—but with the amplitude evenness of transistors like our FirstWatt champs. On feel as the dominant quality or climate, it was unmistakably tube sound. On utter absence of noise, complete bandwidth and linear behaviour relative to the mechanical nature of loudspeakers, it had typical transistor strengths. Those aspects could be readily inspected and confirmed with a simple act of attention. Unless held on to however, they simply receded again into the overriding evidence of valve gush and redolence.
This clearly differed from the Trafomatic Belus hybrid. Back when, its solid-state aspects had dominated the temporal domain. It moved across time more rigidly and tight. The EHTs reminded me now of far more my friend's rare Berning Siegfried. Its 300B couple not through usual output transformers but tiny RF equivalents which step down an ultrasonic carrier wave. Radically different from my earlier Yamamoto and Woo 300B amps, Dan's Berning does it quicksilvery fast and fully exploded across the bandwidth. So does Vinnie Rossi's spud circuit for his L2 preamplifier and LIO DHT. Now the Thöress exhibited that type of aroma. Relative to the Berning, I merely suspected even more significant tonal mass from Reinhard's antique ½ 6SN7, the latter being colloquially known as a big-tone tube. With my widebander concept trending into leanness with ill-matched electronics, hearing the total opposite rather pointed at the 6J5. Attempting to roll them after a few minutes of play then power off will spell burnt fingers sans cloth or gloves. As Reinhard explained, their bigger cathode for generous emissions really does play miniature fission oven.
The sound's phenomenal openness meanwhile seemed directly tied to MIA phase-shifting bandwidth-limited output transformer windings. This quality incidentally expressed itself well beyond the confines of the listening chair. Even in the adjoining open kitchen and back out into the large foyer at my office desk where stereophony has long since gone out/through the door, this difference from the SIT1 communicated. If that suggests the perfectly balanced hybrid aka super mutt, I'd agree. Now we have the basic picture. With a pair of interstage-coupled Allnic PX25 monos and a Tektron SET integrated inbound for their own reviews, direct A/Bs against traditional direct-heated triode circuits with output transformers and lower power were next. But first, how would the Thöress do into our Audio Physic 4-ways? Here I'd not even bother with either of the pure tube SET. Entirely the wrong tools for the job. To measure climate change for the EHT, I'd now use our LinnenberG Liszt. Those are premium 200-watt 1MHz DC-coupled lateral Mosfet push/pull monos. With SIT1 our resident top amp for Nenuphar now outclassed by the Thöress, Liszt is our premium Codex driver. How much of Reinhard's expertly set 6J5/Mosfet flavour would translate? How much and where would it shift given a now very different far more challenging load?
