Astraeus

Reviewer: Simone Ragionieri
Source: Generic 5G router into Taiko Audio network switch both powered by a Zayin Audio Suprareg; Taiko Olympus XDMI Server; LampizatOr Horizon 360 DAC
Headphone amplifier: Solaja Audio Master 300b [on review], Riviera Audio Labs AIC-10
Headphones: Nur Harmonia [on review], Spirit Torino Valkyria, Raal 1995 Immanis
Loudspeakers: Diesis Audio Aura SE
Cables: complete Faber's Cables La Potenza loom
Power delivery: Faber's Cables La Potenza power distributor and ground box, Furutech NCF AC wall plugs on a dedicated spur
Room size: 5 x 4.5 x 2.7m
Room treatments: Eight ceiling diffusers, floor-to-ceiling acoustic curtains on sidewalls, Vicoustic VicTotem Ultra VMT in front corners
Review component retail: €9'400 ex VAT

What comes after Armageddon? The location for the Bible's mythical end-time battle is how the prior flagship head/speaker amp from Serbia's SAEQ was named. To eclipse it—perhaps the morning after that battle with a glorious peace treaty—we now get Astraeus, a Greek god with plenty of celestial offspring. As previewed in my Armageddon review, Astraeus runs a conservatively biased long-life single ECC88 input stage with two heater-voltage settings followed by a 99-step fast-acting remote-controlled precision attenuator, MKP coupling caps, a Germanium interstage, output transistors sans ballast resistors hence no degeneration as that "other form of feedback" as Nelson Pass calls it, Armageddon power with 3 x the quiescent current for up to 5W of class A bias and an innovative memory function ideal for when comparing two headphones of wildly different sensitivities.

"The input tube without output transformer will move us towards a new tonal balance whose greatest effect will be at higher SPL for a deeper level of relaxation without loss of resolution. With this project I support the general nostalgia for tubes. With hybrids, the most important thing is to retain that authentic tube sound and preserve its magic of space and refined micro detail without too much sweetness. The goal was to bring the sound into the zone of physiological hedonism which tubes generate. And that's what happened. This playback is lively, fluid with a beautiful presentation of the third dimension of space. I wanted to optimize the potential charm of the tube with the power resources so easily provided by a fast semiconductor output stage with low distortion.

"I would like to mention a few details of how I realized my wish to preserve the authenticity of the tube sound with the concept of a hybrid of very serious potential. The input stage is practically a tube buffer with high 8-9mA bias meant to run ECC88, E88CC, 6DJ8 or 6922. That connects directly to your source signal to not degrade through an attenuation system. The input sensitivity is about 2V peak to peak for full power. The overload limit is about 7.5V peak to peak. After this tube input buffer comes the volume control in 99 steps. We removed its semiconductor note with Germanium transistors between input and output stage to preserve the authentic tube flavour. It is indeed a real loss for audiophiles to have stopped costly Germanium transistor production when those parts offer a sonic nobility that classic silicon transistors lack. Our Hyperion Ge amplifier is an outstanding example of that physiological pleasantness without too much sweetness or losing resolution to offer a type of sound that appeals to many. That's why I decided to revisit Germanium transistors in Astraeus. Finally, the silicon output stage runs initially in class A with little coloration to not overlay the influence of the tube sound. This is one of the biggest hybrid challenges that must be taken very seriously. All listeners to the prototype confirmed unequivocally that we absolutely managed to preserve an authentic tube sound without excessive glazing that would round off the edges of images, curtail the breathiness of vocals and take away the air flow on a saxophone.

"Astraeus is capable of 20wpc into 8Ω and 30wpc/4Ω from a 150-watt transformer that's 50% larger than Armageddon's. I don't believe you will ever need a preamplifier. The connector system on the back is of much higher quality than Armageddon. Raw power isn't the primary decider. Astraeus is more refined, lively and has that physiologically seductive presentation of tubes." One of the listeners to the prototype was Raal's Aleksandar above who clearly enjoyed his time with Astraeus over his own Immanis triple-ribbon earspeakers. And to give Cap'n Obvious his due, the new remote control adds legs to Dragan's hope that more people run his dual-use models with appropriate speakers. Now that volume is adjustable from the seat, justifiable reluctance born of laziness just got smoked. This isn't just a super-ambitious headfi amp. It has equal ambitions as a speaker driver. About his choice of tube: "Tube selection is complex. You must listen to several favourites, spend hours and hours, days and days on just one change to get the sound you're after. Personal sensibility is a determinant. There's lots of talk on tube types but the circuit context in which you apply the tube is most important. There are many tube amps using the ECC88 but with an average sound that doesn't excite. The method of application, choice of surrounding components, the entire construction of the amp all set the final sound quality. It's not just the type of tube. It's like cooking a dish. Sometimes excellent ingredients don't give the good taste we wanted but add a little more salt and chili and it becomes fantastic. Too many pictures with great parts don't tell the story. That's why you choose a restaurant where you know the chef can really cook. It's the same with amplifiers. It's not the parts which decide but the overall design and ultimately the chef. My recipe maximizes the single tube's flavour by placing it directly at the input where it sees a 2-3V signal against its own negative gain to transfer the full tube contribution to the output stage past the attenuator. Compare that to a typical head amp with 20-30dB voltage gain where the input stage must generate just 0.2-0.5V of gain to reach full output. That reduces its sonic influence. I wanted the opposite, hence a tube buffer. I also don't recommend DAC voltages greater than 2-2.5Vpp to not restrict the proper range of our attenuator."

As an interim teaser from Alex whilst Dragan formalized the prototype, "the sound was fluid, lively, full of detail and body, simply amazing. Relaxed yet full of life. It sounded correct in tone balance, it sounded correct in every way and I could easily live with it for a very long time. We were rolling interconnects and DACs. It was easy to recognize different cables, DACs were showing a world of difference, enough that I could easily tailor the sound to my preference. And we rolled two different tubes, EI ECC88 and Tesla ECC88. I did prefer the EI for its fuller sound. I was looking in my stash for more tubes but couldn't find the box, so my tube rolling joy was cut short but not to my dismay. For me the EI was phenomenal as was the Astraeus as a whole package. I liked a lot those two memory settings on the volume control. Basically you can listen to wildly different headphones regarding sensitivity and quickly swap for A/B testing. Just set the volume for one, memorize it, set the volume for the other, memorize that, then tap the knob as you swap headphones. Voilà, same volume. Very good stuff. I am most happy to witness this leaps-and-bounds evolution in SAEQ's sound so congrats to Dragan for this wonderful new amplifier!" At the alternate Hifi Deluxe show at the Munich Marriott, Dragan even demo'd Astraeus over two Immanis plus a dynamic headphone, simultaneously.

After Munich Dragan had this: "I'm pleased to report that the Astraeus promotion at the Hifi Deluxe was very successful. We shared with Raal and used their Immanis for amplifier testing. We never experienced so many lovely comments and excited impressions to the point that some visitors declared the Astraeus + Immanis combo to probably have the best sound at both Munich trade fairs [MOC and Marriott respectively – Ed.]."