More than half a century later, blind dates—now with review equipment—remain fraught. Sure, expectations and the frisson of unknowns heighten the experience, but if it isn't a good match, I'm stuck for the duration of our time together. If a component sounds so mediocre that I can't be sure what's on a recording, the review and my joy are compromised. When music's emotion and beauty remain locked within cascading successions of bits or tightening spirals of grooves, it feels as though once again I've been sent out into the cold.

I first discovered Octave's towering Jubilee Mono SE monoblock ($80,000/pair) at AXPONA 2022, in the listening room sponsored by Dynaudio of America. In that first encounter, I found the sound so disappointing that I hesitated to accept an offer to review it. When I later learned that this poor showing was related to an unfortunate—indeed tragic—event, I promised to return once the setup was complete. When I did return, the next day, the transformation was dramatic. That system delivered "captivating beauty ... with all the soundstage depth, air, and expanse one could hope for," I wrote in my AXPONA 2022 show report. "Beauty without bounds."

I promptly said yes to the review. Then, mere days after Dynaudio of America President Michael (Mike) Manousselis visited my home to help install the Mono SEs, I was off to Munich High End. There, I heard the monoblocks for a second time, with a different front end and loudspeakers. "Timbres sounded extremely natural and inviting on vocal and chamber music by Claude Debussy," I wrote in my May issue show report. "The sound [was] all that I could ask for. ... [C]olors and depiction of space were stellar." I was eager to return home, finish writing my show reports, and start listening to the Octaves.

Octave's history and designs Founder, owner, and designer Andreas Hofmann dates Octave's beginning to 1968, when his father, a specialist in transformers and high-frequency tube technology, founded a company to manufacture ultrasonic power transformers. Three years later, when Andreas was 14, he applied all he'd learned from his dad to building his first amplifiers. Five years later, after finishing school, he decided to go further. "I got in touch with the high-end scene, studied and listened to a lot of tube amplifiers, and decided to develop my own designs," he wrote. "I wanted to overcome some issues with the 'classic' tube scheme and increase user-friendliness and long-term reliability. I also wanted to develop power amplifiers that are uncritical in relation to the speaker."

Octave released its first model, the HP 500 tube preamp, in 1986. Over time, production expanded to include preamplifiers and integrated amplifiers. Octave has always produced all the components for its products in-house to ensure quality; that includes winding its own power supply, output, and step-up transformers. In 2021, while the COVID pandemic was raging and high-end sales were climbing, the company moved into newly constructed manufacturing and warehousing headquarters.

An in-person chat at Munich High End with Hofmann and Thomas Brieger, Octave's head of sales and marketing, revealed that the company's Jubilee Mono SE is a new design, based on a pentode push-pull system Hofmann designed 20 years ago.

"I wanted to optimize and find the limits of the pentode design," Hofmann said. "My concerns were not limited to power. I also focused on the naturalness, the clearness, the dynamics, and the stability of the amplifier against a complex load. The second-generation Octave SE, which uses multifeedback, represents a refinement of the push-pull technology. There is also a completely new output transformer with a better phase shift that improves the feedback and the total phase of the amplifier design. I also chose the KT120 over the original version's KT88 because it was reliable and good-sounding, and it enabled me to raise the output power to 350–400W into 4 ohms and maybe 300W into 8 ohms.

"From the beginning, I've done true pentode designs rather than ultralinear or triode. Ultralinear was developed in the 1960s as a means to rival solid state performance. Ultralinear may give you a little more output power and lower distortion, but in my opinion, it kills the tube. The tube is always overstretched, and lifetime is reduced. It is one of the reasons why the tubes sometimes blow out.

"In contrast, pentode technology conforms to the tube; it doesn't overstretch it. Pentode amplifiers also have completely different load characteristics. Ultralinear is very, very sensitive to the load; pentode is not so sensitive. ... Bob Carver once made a pentode design, but he stopped it. I may be the only one doing this type of pentode amplifiers now."

Hofmann claims that Octave's pentode designs have better phase stability and phase response, which is important for designs with negative feedback loops. He also believes that in pentode designs, feedback works better, amp stability is increased, and dynamic stability improves, as does the sound of mid and high frequencies.

"I don't use chokes or old-fashioned parts in the power supplies," he said. "I've developed very, very stable new optimized power supplies that are solid as a rock and have low distortion and very high-power capability. Many designers use chokes to tune the sound and make it warm. This can make the amp a little bit slow. I don't want this. I want the sound as natural and precise as possible; I don't want it too warm or too soft.

"Even without a choke, you don't hear hum noise. People always use chokes to get rid of the hum, but I get rid of it using other technologies. In my opinion, it's easy to design an amplifier that has no hum and has no noise. It's about the total: the wiring and the ground system. It took me a long time to optimize it."

Thanks to the Mono SE's special output transformer, which is optimized for push-pull, its output remains stable down to about 2 ohms. "The transformer has very high symmetry of both tube windings," Hofmann claimed. "Think of it as a symmetric tube input to an unbalanced speaker circuit. Phase shift is precisely controlled. Most people use output transformers with 4-, 8-, or 16-ohm taps. Because no speaker presents a stable load with average impedance, our output transformers have only one output winding that is optimized for average impedance, let's say from 3 to 12 ohms. This is why we say the Jubilee SE mono outputs 400W into 4 ohms, depending upon the power supply characteristics, and an average of 300W into 8 ohms. The amplifier remains stable from 3 to, let's say, 20 ohms. Nor does it oscillate with a low-impedance or high-impedance load. If demand gets too high, the amp's electronic protection circuit switches it off."

Octave's models use a mix of JJ and Russian tubes. Despite parts shortages and concern over future accessibility of tubes made in Russia (footnote 1), Octave's policy of stocking up at least a year's worth of parts has kept production constant.

Due to the ease of bias adjustment and the protection system, the company claims that tube rolling won't damage the amplifier. "If there's a lousy tube, the protection circuit goes on," Brieger said. "We have a solution that minimizes stress to tubes, capacitors, and resistors. When you switch on the unit from cold, we initially build up the voltage very slowly and keep it below the specification. This avoids blowing fuses and tripping circuit breakers during this critical time and greatly expands the lifetime of the components."

"My designs are always a bit conservative; the amps don't get very warm," Hofmann added. "Because I don't overload the tube specs, I expect a tube lifetime of 5–8 or [even] 10 years. The unit turns on in three phases. When you [first] turn it [on], the current is limited to the mains and limited and regulated to the cold tube, so it comes slowly. After the tube is warmed up a little bit, we switch on the plate voltage to avoid stress in the cold tube. This extends the tube's lifetime. It takes 15 minutes to go from totally cold to getting the full sound.

"The amplifiers are bulletproof. My designs have extreme stability against load, because we know the stages inside, and we monitor the current and voltage. You can short-circuit the speaker or remove cabling, and it will make no difference. You can also switch our amplifiers on and off even if there's no speaker connected. Others say you should wait 7 or 8 minutes after you turn off a tube amplifier before you switch it on again, but because we perform startup and shutdown in a very controlled manner and follow the same procedure when we turn it on and off, you can turn it on and off without concern."

When I tried to talk about specific parts choices—for example, what internal wiring Hofmann uses—he replied, "I don't like to talk about this, because I don't want to get into these holy cow discussions that are endemic in the audiophile community over the capacitor being a silver foil capacitor or something else. Of course I listen to different wires and capacitors, but I don't want to make a philosophy out of it. Beyond the type of wire, the whole wiring system, distances, AC and DC connections, and the signal flow are of very high importance. Finding the best wiring schema can take a very long time. Thanks to the Audio Precision measuring system, we can analyze a lot inside an amplifier. But I can tell you that most of the critical small-signal connections are on a printed circuit board."

Brieger chimed in. "When you achieve the right angle and distance between the power supply and output transformer, specifications improve. After 40 years, Andreas can look at a PCB or inside a cabinet and immediately know how to place the parts and how to arrange them. It's not a secret that we use EPCOS capacitors, formerly made by Siemens.

Footnote 1: As noted in Julie Mullins's June Re-Tales column, Russian-made tubes used in Western hi-fi equipment—the Tung-Sol, Electro-Harmonix, EH Gold, Genalex, Gold Lion, Mullard, Svetlana, and Sovtek brands—are produced in a Russian factory by US-owned Electro-Harmonix.

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