50 watts of Class-A tube power per channel is a statement. But the Octave V70 Class A not only impresses with high power, but also with sonic maturity and finesse.

In brief
“Octave cannot deliver sound gimmicks or coloration: The V70 Class A captivates with neutral, highly accurate music reproduction. Its dynamics are exceptional for a tube amplifier, as is its universal compatibility with almost any high-quality loudspeaker. The extremely meticulous build quality and circuitry optimized for reliability make this German amp a lifetime investment.”

Advantages
+ Fine, precise sound with plenty of dynamics and spatiality
+ Automatic bias adjustment
+ High power for a tube amp
+ Wide selection of output tubes
+ Eco mode to save energy

Disadvantages
– Heavy, hot, and power-hungry
– Remote control without source selection

Our listening room gets warm because we have invited the Octave V70 Class A tube amplifier for review. Like all Class-A amplifiers, it is power-hungry, but promises things that stand in stark contrast to classic tube amps: almost unheard-of power reserves and stoic composure when it comes to speaker selection. Is that true – and how does this tube behemoth sound? We tested it for you.

Much “bias” about tube amplifiers
From the perspective of the HiFi mainstream, tube fans might be considered eccentric loners who deliberately make life difficult for themselves: They bring bulky, power-guzzling devices that operate with dangerous high voltage into their homes, devices that constantly need something checked and whose critical components must be replaced every few years.

Then, for optimal sound, these electronic prima donnas also require very specific loudspeakers, of which there aren’t many and hardly any affordable ones. And if you want to rock out properly at a party, the glowing fetish amplifier has to make way for a mundane transistor due to lack of power. Even if there is a grain of truth in it: tube listeners usually have better things to do than fight against such technical myths. They prefer to remain silent – and enjoy.

Experience shows that tube enjoyment is particularly unspoiled when the amplifier comes from Karlsbad in Baden, at the northernmost foothills of the Black Forest. There, Andreas Hofmann runs his amplifier manufacture Octave, which itself emerged from his parents’ transformer factory. The output transformers are the most fundamental and quality-determining component of a tube amplifier. And Hofmann learned how to build them, so to speak, with his mother’s milk.

We have ordered one of his best integrated amplifiers for testing: the V70 Class A. But ultimately, the exact model isn’t so crucial: all Octaves are characterized by Hofmann’s pursuit of absolute reliability, everyday usability, and sonic neutrality. You won’t find sound tricksters or delicate watt-wimps among them. The V70 Class A, during our listening test, certainly brings the unmistakable sound of its special circuit variant, but not its notorious inefficiency.

Octave V70 Class A listening test: Power, warmth, and transparency
First, we play a very delicate production on the Linn Sneaky network player, which has almost no macro-dynamics but incredibly noble tone colors and fine structures. Where To From, the new album by Icelandic composer and cellist Hildur Guðnadóttir, bathes us in harmonies of cello, viola da gamba, and viola, entwined with vocals by Guðnadóttir herself and two other female singers. After a few minutes, it becomes clear: no transistor amplifier we know can manage this level of elegance and softness, almost tenderness. Especially since this gentle elegance does not come at the cost of accuracy: you hear every square centimeter of wood, every vibrating string, every breath – with the contrast of an ink drawing, but also the airy lightness and nuanced richness of a watercolor.

Comparison devices are not easy to find if they are to stand at least a ghost of a chance. On the transistor side, we have the McIntosh MSA5500. It sounds somewhat darker and less finely resolved, but impresses us again with its microdynamics and smooth musical flow. In the tube camp, the Cayin Jazz 90 volunteers and comes quite close to the Octave. It lets the horsehair of the bows glide over the strings perhaps a bit rougher than the noble amp from Baden, but that one is also three times as expensive. If the money is there – no question: then the sensuality of the Octave’s sound is our choice.

Feel free to turn it up
Sortilège by Preservation and Gabe ‘Nandez is significantly more demanding dynamically. An album from Tidal’s recommendation list that initially reliably repels us with its brittle, often dissonant multi-layeredness. But just as reliably, it then draws us into a world of samples, noise, spoken word, and breakbeats. With the Octave, the music sounds so open and spacious even at low volume that we don’t want to turn it up at first. Our fear that the complex soundscapes might then lose stability and order is unfounded: a right turn of the thick aluminum volume control simply makes the beats bigger, the samples more ominous, and the rap more incantatory. But the beautiful timbre and fine differentiation remain fully intact.

The Octave also clearly contradicts the rumor mentioned at the beginning that tubes are not party-proof. To that end, we give it a more demanding task: Paul Kalkbrenner’s elegant techno and house album The Essence. The irresistible banger Que Ce Soit Clair, to which Belgian rap star Stromae contributes his vocals, kicks hard and crisp as it should. The source here is not the streamer, but our hefty Acoustic Signature turntable. We installed a demanding MC cartridge (Transrotor Figaro) to test the built-in MC preamp of our test amp. Unsurprisingly, this too does its job perfectly.

Octave delivers Class-A sound without its drawbacks
Class A means a continuously high quiescent current that keeps the output stage in its ideal operating range. In push-pull amplifiers, this can completely avoid the distortions that occur in AB mode at the transition between the positive and negative half-wave of the output signal. Because the quiescent current is fully cranked up, this transition no longer takes place: the output transistors or tubes are permanently under full load. However, this leads to enormous heat generation and high stress on the power supply. With tubes, which are already more forgiving in terms of crossover distortion than transistors, this circuit variant is therefore rarely used.

Andreas Hofmann did not build a standard Class-A amp with the V70, but rather a special form with “Dynamic Bias Control” – a floating, power-dependent adjustment of the operating point. Thus, we get an amplifier that largely operates in Class A, yet simultaneously has power reserves that would actually require a twice-as-large amp. You could also say: Hofmann cheats. Or better: he conjures. And so masterfully that nobody in the listening room notices. The V70 Class A can easily unleash 50 watts per channel. That’s slightly less than the classic A/B-tech V70 SE, but it’s gigantic for a Class-A amp that weighs “only” 22 kilos.

Tube-friendly and reliable
The exact power output also depends on the tubes used. As standard, the amplifier comes with two pairs of the modern beam tetrode KT120, but it can also adequately supply the larger KT150. Even the hefty KT170 is technically compatible, but it cannot be sold as factory configuration because its XL glass bulb no longer fits under the prescribed protective cage. Conversely, owners of sufficiently efficient speakers can also experiment with pin-compatible smaller tube types. A recessed switch on the back allows you to lower the plate voltage of the V70, expanding the selection to types such as EL34, KT88, and 6550.

Typical of Octave, the V70 Class A electronically monitors its tubes. A tube defect or incorrect operation practically cannot take half the amplifier with it, thanks to fast protection circuits. A precisely controlled power-on management gently ramps up the vacuum tubes. Only when everything is running stably, after about half a minute, a relay releases the speaker outputs.

On the newly arrived test unit, we searched in vain for the small trim pots for manual quiescent current adjustment that we were used to from older Octaves. No wonder: the V70 Class A automatically adjusts its quiescent currents. However, if you turn the input selector all the way to the left, the four small LED bias indicators in the display window still light up. But they now only serve to confirm that the automatic system is doing its job correctly.

Octave V70 Class A: Upgradeable and connectivity-friendly
The V70 Class A’s richly equipped connection panel is rather atypical for a tube amplifier. The basic version offers four RCA inputs and one balanced XLR input. Analog fans can order a phono preamp module for either MM or MC, which is then accessible via the Aux-2 RCA pair. We already know a similar concept from the T+A PA 2000 R. Another input leads directly to the power stage and is intended for operating the V70 with, for example, an AV processor. Outputs include both a fixed-level Tape Out and a variable Pre Out. The extremely solid speaker terminals from a German laboratory equipment manufacturer, on the other hand, are only available in a simple version: Hofmann nominally designs his amplifiers for 6 ohms, but they get along brilliantly with speakers of practically any impedance.

In addition to the IEC power socket, the Octave surprises us again: a screw cap covers a peculiar four-pole connector. This is where the optional “Super Black Box” connects. An external housing filled with coffee-cup-sized electrolytic capacitors, which quadruples the filtering capacity of the internal power supply and makes the bass grip even noticeably more iron-fisted. It’s not strictly necessary, nor particularly cheap. But it’s a wonderfully decadent upgrade option that you can treat yourself to either right away or sometime later.

Handmade in Germany at the highest level
We’ve already mentioned that Andreas Hofmann winds his own transformers. But even what he cannot make himself comes from the finest sources at home and abroad, with local suppliers taking precedence. Thus, the perfectly milled, painted, and brushed metal parts come from a company in Baden. The workmanship is not unnecessarily flashy, but perfect in a purposeful, unobtrusive way – more Unimog than Ferrari. This also translates to reliability and robustness: Hofmann’s amplifiers are completely unpretentious, don’t shy away from any nasty speaker load, and have earned a reputation for absolute indestructibility over the past 40 years.

Octave has even thought about energy consumption – a topic often neglected by high-end enthusiasts. If you activate the “Eco Mode” with a switch on the back, the amplifier deactivates its output stage after about ten minutes without a signal, but immediately and gently ramps it back up as soon as you want to continue listening. This not only reduces power consumption during sleep phases by 85 percent but also extends the life of the output tubes. So it’s perfect for when you want to listen to a side of a record now and then during the day. Which is guaranteed to happen often with the V70 Class A.

Our verdict on the Octave V70 Class A
Legendary durability, exquisite sound, and exceptionally stable power characterize the Class-A integrated amplifier from Octave. Experimentally inclined audiophiles will appreciate the many compatible tube types that the V70 Class A supports. At the same time, extensive protection and control circuits reassure even the most cautious music lovers. The fact that development, manufacturing, and many upstream production steps take place in Germany naturally affects the price. But it also results in a 110 percent perfect and wonderfully sensible build, along with well-thought-out, mature concepts that you can feel and enjoy with every interaction with the Octave.

Technical Specifications
Power: 2x 50 watts / 4 ohms (High), 2x 25 watts / 4 ohms (Low)
Inputs: 4x line RCA, 1x XLR, 1x Pre-In (RCA), optional: Phono MM or MC
Audio outputs: 1x pair of speaker terminals, Pre-Out (RCA), 1x Tape-Out (RCA)
Dimensions (W x H x D): 451 x 150 x 415 mm
Included accessories: Tube cage, remote control (volume only)
Weight: 22.1 kg
Chassis finishes: Black, Silver