Octave V70 Class A test: tube integrated amplifier with a fine tone

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Date: 2024-03-26

The Octave V70 Class A attempts a special balancing act: It wants to be an integrated amplifier that combines the precision of the transistor with the tonal beauty of the tube and the Class A circuit. That worked out pretty well...

The tube specialist Octave has created its own league in the world of hi-fi: tube amplifiers that not only sound “nice”, but also particularly authentic. That has always been the approach of Octave boss Andreas Hofmann, who can lament for a long time about today's sound zeitgeist. Hofmann: “Today, a lot of things just have to sound nice. That's not my way. It has to sound right to me. Because beautiful sounding tube amplifiers are usually far too dependent on the connected speakers. Octave integrated amplifiers must sound good on all good speakers.”

Hofmann has proven this universality many times; His V80 SE was the amplifier reference for LowBeats for a long time. And although (or perhaps because) he is an absolute tube specialist and owns a winding system for transformers, Hofmann does not rely exclusively on glass bulbs. Semiconductors are also used where it makes sense - simply because they sometimes provide much better long-term stable working conditions.

And that's exactly what makes an Octave special: you always know that you'll make a friend for life. I have had two Octave components over the past few decades: the HP 200 preamplifier and the V40 integrated amplifier. There was never anything about them...

For this longevity, the Octave V70 Class A presented here has a few peculiarities that also distinguish its brothers. For example, there is electronically monitored overload protection, the controlled ramp-up of all heating and anode voltages and, last but not least, the so-called ECO mode, which switches off after a few minutes without a signal in order to gently restart with a signal. We know this from modern subwoofers. But such a life-extending mode is particularly useful for tubes.

The special features of the Octave V70 Class A
The V70 SE is a long-standing member of the Octave family. The biggest difference to the newer Class-A version is already in the name of the amplifier and makes high-end drivers sit up and take notice: Class-A.

In principle, Class-A has disadvantages in tube circuits - namely more components in the signal path. The concept with the higher quiescent current also sounds different, often even a little less dynamic than a classic push/pull setup - also because it necessarily has less power. But most music lovers find the Class A sound to be more pleasant, rounder and finer. Hofmann: “Technically it’s actually a step backwards, but sonically it’s a step forward…”

That's why he's happy to take this step, but garnishes his Class A circuit with a few subtleties. Hofmann developed the “Dynamic Operating Point Setting” (DBC). Behind it is a self-regulating Class A amplifier, which, if necessary, leaves its Class A range and then continues to work in the Class B range with a significantly lower quiescent current.

Is there cheating? “A little bit,” Hofmann replies with a smile. “But it’s better if the V70 Class A doesn’t have to round off the upper dynamic peaks, right…? He's right, especially since the takeover distortions of classic A/B circuits are not as big an issue with tubes as they are with transistor amps, where these takeover distortions sound unpleasant from half-wave to half-wave. In any case, the DBC concept has proven itself so well that Hofmann wants to continue pursuing this line very soon.

Practice
The mere fact that I am including a section on the topic of practical friendliness with a (actually simply equipped) tube amplifier shows the exceptional position of the V70 Class A. For example, there is the auto-bias circuit: A controller in the amplifier can adjust itself to the four inserted power tubes. That is laudable. Anyone who knows Octave devices: The tried and tested BIAS measurement, which showed the status with the colored LED traffic light and was adjusted using a screwdriver, is still available, but only for functional testing.

The functions of the V70 Class A are comparatively diverse. It offers 6 x high-level inputs, a regulated preamp output and the option of integrating the amplifier into a home cinema system. The settings for the ECO mode and the power range (Low/High) can also be found on the back.

And that brings us to another special feature of the Octave. The V70 Class-A can be operated in two optimized performance states: in “Power High” or “Power Low” mode. Since this is a Class A amp, the power output is naturally lower than with standard push-pull circuits. Our test model was equipped with the powerful KT 120; With it (or a KT 150) you can get the maximum performance (around 50 watts per channel). If less power is required (i.e. around 20 watts per channel), you can move the red switch on the back of the amplifier to “Low” and this will also optimally control a weaker tube like the 6550. Hofmann: “The 6550 from JJ in particular are comparatively cheap and sound really good.”

Of course I tried it out and luckily found a pair of JJ 6550 tubes in my stash. Result: Hofmann is right. The V70 Class-A sounds a bit finer with the 6550 in low mode. The KT 120 is an excellent tube, but there are even better ones out there. And if 20 or 25 watts are enough...

And then there is the possibility of expansion via the so-called black boxes. Hofmann sent me the large Super Black Box (price 2,400 euros) to try out. Thanks to a battery of twelve high-performance capacitors, it quadruples the sieve capacity of the V70 Class A. This expansion of the power supply not only increases the impulse power, but also the ability to drive electrically difficult loudspeakers much better.

During the listening tests we mainly used our two loudspeaker references, the FinkTeam Borg and the AudiaZ Opera belongs. The V70 Class A drive both confidently up to the expected level limits. However, its performance with the Super Black Box connected was noticeably better in both speaker cases.

It's not just about better bass control - of course that's also an added factor. No: Rather, the room opens up further and the entire sound image seems to emerge a little more effortlessly. Knowing full well that the V70 Class A will be a good 25% more expensive as a result, my urgent recommendation is: please go with it!

Hearing test
The listening tests were then carried out almost exclusively with the Super Black Box connected and with the more powerful KT 120 tubes. And in this configuration, the V70 Class A sounded pretty much as I expected. Despite tubes (which basically have a little less bass control than transistor amps due to their high impedance) and despite the class A circuit, which sounds even nicer and warmer, the Octave offered a downright refreshing bass performance. During the electro-pop classic “Oh Yeah” by Yello, he pushed the sub-bass into the listening room so forcefully via Audiaz Opera that we initially looked at each other in disbelief: Does a tube like that play with just 50 watts? Usually not.

Especially since it's not just about the bass: The Octave celebrated a wonderfully finely chiselled, very open sound in which all the details are precise but not superficially fanned out. I'm a big fan of Andrea Kleinmann's "Saitenwind", a solo harp recording in the monastery church in Lorch that has a great sound.

The recording from the summer of 2023 was made by LowBeats colleague Jürgen Schröder. That's why I was relatively close and know what it sounded like there. And all I can say is that the recording with the combination of V70 Class A and AudiaZ Opera came damn close to the recording moment. The strings swayed so naturally, so finely, so effortlessly and at the same time so physically; the whole instrument was noticeably in the room. I can't remember ever having heard the work so authentically before.

I was so excited that I listened to the harpist's entire CD - even though the CD is quite short. To ground myself a bit, I pulled our McIntsoh classic off the shelf. The MA 7900 is no longer the latest and is no longer in the American range. And yet it represents this special American way of sound, which is still very impressive: always touring comfortably warm from below, but always extremely strong when you press the accelerator.

But even though the Mac has at least four times the performance of the Octave, this was only noticeable at very high volumes. At normal to higher levels, the tube amp often seemed a bit faster and more powerful. And it always sounded a lot more open and finer in the mids: voices had a very special (should I say “beautiful”?) flair with the Octave. Everything had such a pleasant clarity and velvety quality. This is extraordinary.

Of course we also heard the V70 Class A against our current amplifier reference, the Westend Audio Monaco. With its 2 x 100 watts it is actually a bit more agile and allows the bass drums to bang even tighter. It also gave an even more stable impression of space. The Octave doesn't sound quite as grippy, but in many places it gives a slightly more cultivated subtlety - for example when it draws the harp strings a little more finely. Either way: You are operating at a very high level here.

Conclusion Octave V70 Class A
Class A: HiFi connoisseurs know the advantages of this circuit concept, which generally sounds finer and cleaner due to the lack of crossover distortion. However, Class-A also stands for high power consumption and low performance, and so Octave boss Andreas Hofmann has devised his own type of Class-A, which, in case of doubt, leaves it alone and opens up a greater scope for performance.

Another example of the “German” approach to the subject of tube amplifiers can be seen in the diverse and clever equipment as well as the fact that this amplifier is likely to have a long life thanks to flawless workmanship and tried and tested “gentle” circuits

Ultimately and above all, the Octave V70 Class A is an excellent, natural-sounding tube integrated amplifier that undoubtedly occupies a special position in its class and also keeps the audiophile's instinct to play alive with a variety of options for trying out and sound tuning...