Integrated Amp Reviews

It may be strange to read what I'm about to say in the pages of Stereophile, but it's the cold hard truth so here goes: Audio reviews are inadequate. They don't tell the whole story. They come up short and can even misdirect.

It's not their fault, or at least sometimes it isn't. Even the good ones can't tell you how something will sound to you—let alone make you feel, the ultimate point—in your own room. As helpful as they may be, they can't address the elephant in the listening room: synergy.

Have you ever been to an audio show where a component in a demo sounded wonderful, only for that same model to sound average or worse at the next show, or, God forbid, in your own system? The truth is that most components these days are well-designed and sound good, so why don't all exhibit rooms sound great?

There's no better example of a truism in our hobby than that a well-set-up $10,000 system will sound better than a badly set up $100,000 one. Money can only go so far. Synergy goes further—among components, with the room, the recording, the listener's tastes, the foundation under the equipment, the tubes, and on and on. Even electrical power enters in: Recall another audiophile truism, about how your music often sounds so much better late at night. (The explanation usually given: The power is better late at night.)

In both cases, the reason is synergy. The greater the synergies we achieve in our listening environment—more synergies and more synergistic—the better the music sounds.

In reviewing the Octave Audio V 70 Class A integrated amplifier ($12,000 and up; $15,900 as reviewed), I was reminded of the importance of synergy in our hobby.

Octave Audio
Germany-based Octave Audio's origins date to 1968 when it began as a transformer-winding factory called Hofmann, after founder Karl Heinz Hofmann. In 1975, Hofmann's son Andreas, an audio enthusiast with "electric current in his blood," to quote the company website, introduced hi-fi into the family business by building and selling his own amps, initially under the Hofmann name. Then, in 1980, the company rebadged his wares with the Octave logo. Not until 2000, when Andreas took over the company, was the Hofmann brand changed to Octave Audio. Today, the company builds transformers for OEM companies, though only a few.

Octave Audio released the class-AB, 70Wpc, push-pull V 70 integrated amplifier in 2003. It has been a constant staple of the company's product line and remains so today—only now it has a brother, the 50Wpc V 70 Class A, released officially in May 2020, though the launch stretched into 2022 due to the COVID pandemic. It's the company's third class-A design, after the 8Wpc V16 headphone/integrated amplifier (2017) and the Jubilee 300 B monoblock (2019). As a fan of the sound of class-A, and an enthusiastic owner of a solid state class-A amplifier (footnote 1), I was excited to review the new model.

I was also a little perplexed because this class-A was different—a push-pull design built on a pentode circuit Hofmann developed to surmount what he considers class-A's inherent liabilities: low power, limited dynamic range, and energy-sucking inefficiency. He dubbed this new design Dynamic Bias Control, a souped-up class-A technology with the potential to deliver 50Wpc—and up to 70Wpc when paired with the company's optional Super Black Box Capacitance Power Storage ($3500 each), a power supply–looking device connected to the back of the V 70 that's said to increase the amplifier's capacitance tenfold to improve current delivery and, hence, the ability to drive difficult speaker loads. Octave says it "stabilizes current delivery and reduces the impedance interaction between amplifier and speaker." Better synergy.

I received the Super Black Box as part of the Octave review package. After trying the V 70 with and without it, I decided to do the core of my review with it and, later in the review, report the differences I heard without it. Octave also sells a smaller, less powerful version of the Super Black Box, called the Black Box ($1500), which Octave didn't send me.

Among the V 70's technical features are a 20–30 second "soft start" delay that turns the V 70 on in stages to protect tubes and other critical parts (but especially tubes) from the inrush of high current that can lead to premature wear; an ECOmode that automatically switches on to shut off the amp's tube section after about 7 minutes of detecting no music signal; a home-cinema bypass circuit; a pre-out for connecting to a subwoofer; and an autobias circuit that shows the stages of a tube's lifespan via a multicolored LED layout: yellow for warm-up, green for biased and ready to go, red for kaput.

In the event of a kaput, Octave recommends replacing two tubes—the matched pair it's a part of. An even better (though more expensive) option is to replace all four tubes—both channels. Compatible tube types include the 6550, KT88, KT90, KT100, KT120, and KT150.

Initially, the V 70 was sold with the KT120 tube, but Russia's invasion of Ukraine made that tube harder to get, so it has been replaced by the KT88 as standard. (You can still purchase the V 70 with the KT120 for an extra $400.) I was sent a set of Tung-Sol KT120s (footnote 2) and S4A KT88 tubes; S4A tubes are made in China.

John Quick, of Octave importer Dynaudio North America, encouraged me to start my critical listening with the KT120. One JJ ECC83S (12AX7) (ECC83) and two Electro-Harmonix 12AT7 (ECC81) input tubes complete the tube array. Thanks to the V 70's "protection circuits and soft-start electronics"—that's from the manual—the power tubes are estimated to last 3–5 years, while input tubes should last 10 years or more. I was intrigued by Octave's assertion, also in the manual, that some tubes can require up to 300 hours of break-in to sound their best (footnote 3).

Like Octave's other top models, the V 70 comes with a power selector—a two-position sliding switch on the back of the unit that offers two power-output settings: High (50W) and Low (25W), the former intended for use with more powerful tube types such as the KT120 or KT150, the lower with tubes that produce less power, such as the 6550, KT88, KT90, and KT100, to avoid overloading them. However, since the KT88 included with the Octave was the Carbon Plate High Bias version, John suggested I try the KT88s in the 50W position on the basis that, as per his email, "the carbon plating allows it to be reliable when fed a higher bias level, thereby producing more power in the V 70 when used in the High 50W setting. We don't recommend using standard KT88 tubes in this setting." I tried the KT88 in both settings and preferred the more open and dynamic presentation I got with High 50W.

The V 70 can be ordered in black or silver brushed aluminum. I received black, and I liked the unit's sober, sturdy appearance. However, unless you count two dots that light up to indicate input and power or speaker-mode selection, the screen has no backlight. In my basement listening room with the lights low, I had to use a flashlight to choose an input, or roll the knob across inputs until I heard music. A backlight would be useful, especially one that could be dimmed or shut off during playback.

On the other hand, the volume control I loved at first grope. In my hand it felt like a perfectly weighted, polished mini-menhir. Using it was tactile and intimately physical. This is not a multifunction remote. It has only two buttons, to lower or raise the volume—but what buttons! A soft-rubber mat-like texture, spring-action responsiveness, thumb-cupping comfort—my thumbs never felt so coddled. I wanted to change the volume just to feel it again.

The V 70 comes with a tube cage, but John suggested I remove it during listening because, "even though it's ventilated, a certain amount of acoustic energy can build up inside that little chassis. The cage is there really for safety and import reasons." Besides, the tubed V 70 looks prettier with the top down.

Like every other Octave product, the V 70 class-A is designed and built entirely in Germany.

Listening
With the V 70 fitted with the KT120 tubes, I started my listening with an acid test in which both I and the system are tested: the Cannonball Adderley Quintet's mediocre-sounding CD, Mercy, Mercy, Mercy (CD, Capitol Jazz CDP 7243 8 29915 2 6), an early digital release whose good music I can enjoy only in merciful bites. The Octave made the CD sound relatively good. It took this swinging live set and the noisiest crowd I've heard on disc and made it sound fun.

Before you think, "Oh, the Octave was hiding the nasties with layers of syrupy distortion," it wasn't, or at least, that's not what I heard. I heard the opposite: an opening up, a growth spurt of harmonic foliage coupled with deep-view transparency. The picture was naturally detailed, with radiant tone and images that were more fleshed out than usual. The Octave didn't so much erase the digital nasties as allow more of the music to emerge so that I cared less about said nasties. The Octave perked up this recording, making it sound almost like a remaster of its former self. An amplifier-induced remaster.

The Octave time-stamped the performance on Mercy, Mercy, Mercy—the musicianship, the venue, the giddy crowd banter—by restoring sonic cues. The crowd sounded distinct, giving real personality to the whoops, oohs, yeahs, yelps, the guys-bonding-together exclamations: "What do you think of California now?" It put dimensional measurements to things in space. It made instruments sound physical, impactful, polished, and dynamic, and it placed me on the threshold of the action, maybe 8' from the stage, where my perspective was of hearing band members playing side by side. The Octave radiated the performance, making it big, robust, lustrous, alive, and emotionally galvanizing. I felt like calling the waitress and ordering a beer. Instead, I grabbed one from my minifridge.

When Adderley introduced the title song—"You know, sometimes we're not prepared for adversity"—the lilt in his voice was expressive. His breath against the mike was at once plush and natural-sounding, with real-breath substance. It had shape and denoted it, too: I could picture Adderley's girth and height just by his voice (though who knows if my inner vision was accurate?).

Similarly, the notes emanating from Adderley's alto sax and Victor Gaskin's double bass had meat and tonal shadings. The round, springy note effect in Joe Zawinul's piano sounded timbrally pure, sweet, and delicate, despite the ruckus going on around it. Trumpets were brash and searing, exciting and dynamic. Even the drums, probably the tinniest-sounding instrument on this tinny-sounding disc, had body and were clearly part of a drum set. I could hear the lopsided-oval fluctuations in the movement of the cymbal plates.

We audio enthusiasts like to talk about how a system is akin to a time machine, but is there any type of recording that embodies that better than live jazz? The Octave answered that question for me. It showed me that Mercy, Mercy, Mercy, despite its sonic limitations, was indeed a time machine.

The Octave passed the acid test, as did I. I listened to three tracks straight through.

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Footnote 1: Maybe it's worth mentioning here that the particular class-A (integrated) amplifier Rob owns—the Grandinote Shinai—uses solid state devices in a tubelike circuit, output transformers and all.– Jim Austin

Footnote 2: Tung Sol tubes are made by Electro-Harmonix/New Sensor, an American company that produces its tubes in a factory in Saratov, Russia. Its headquarters, and the factory where Electro-Harmonix guitar effects are made, is in Queens, the New York City borough.

Footnote 3: A couple of years ago, I had a conversation with a designer of tube amps (not related to Octave Audio) in which he asserted that at least in certain designs, tube amplifiers sound much better when they have some hours on them, and in the same conversation that such use causes a degradation in measured performance. Which raises the fascinating notion that in this respect at least, the worse a tube amp measures, the better it sounds.—Jim Austin