Date: 2024-11-25
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.
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.
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.
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 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.
Listening
Desert Lady/Fantasy (CD, Columbia CK 57856) by Toshiko Akiyoshi and her 16-piece Jazz Orchestra, featuring Lew Tabackin. I played three minutes of the first track, then three of the next, the title track. The soundstage was grand: flush with detail, big pictures, and colorful images, except this time, during some parts, its pacing and images seemed to drift more than usual, none of which I had noticed on the Adderley CD, which is a much more sterile-sounding recording than this more harmonically tufted Akiyoshi one...
Tube Rolling
Finally came the moment to AB-test swap the KT120 and KT88 output tubes, and it's at this juncture that the concept of synergy became a theme for this review, because while I expected my tube comparisons to result in a universal winner, that's not what happened. The KT88's generally denser tone, more cut-out imaging, and more realistic timbre suited some recordings particularly well, while with other recordings I preferred the KT120's more panoramic, harmonically developed, bassier, more dramatic presentation. In the end, I chose the KT120s over the KT88s, in part because they sounded a smidge more refined and less grainy than the KT88. That could be because, though I burned them in for 50 or so hours, it might not have been enough.
The wrap
I found the Octave V 70 to be a slightly tweaky component (in view of its several options) that presented music on a grand scale, with vivid colors and shapes and a dynamic momentum that was emotionally engaging. It did a few things that don't often coexist in a single product as well as they did in this one: color, texture, transparency, tonal density, sense of touch, bass heft, and dynamic power. Does that sound like your typical tube amp?
I would say that Andreas achieved what he set out to do: create an amplifier with the soul of a class-A combined with the muscle of high-powered AB. The result is a product like nothing I've heard before, which sounded bigger than life and natural simultaneously. The Octave V 70 had the spirit of cinema vérité in Technicolor. All things considered, I think the $15,900 asking price for the V 70 with the KT120 tubes and the Super Black Box is a pretty good deal.
Basic Model V 70 Class A, optional Phono MM or MC
Tube Complement 4 x KT120
Design Aluminium silver or Aluminium black
Options Phono Input MC or MM
Black-Box and Super Black Box
SPECIFICATIONS
Output power 2 x 50 W continuous, 70 W Peak into 4 Ohm
Frequency response 20 Hz - 70 kHz @ 50 W - 1 / -3 dB
Distortion 0.1% @ 10 W into 4 Ohm
Signal-to-Noise Ratio - 100 dB / 50 W
Optimal Load Impedance 4 - 16 Ohms
Damping factor 5 @ 8 Ohms
Connections
Inputs 5 x Line Level / RCA, 1 x Bypass-Function / RCA
1 x Phono optional / RCA
1 x XLR Input
Outputs 1 x Rec Out / RCA, Pre-Out adjustable / RCA
Features ODT / Octave Dynamic Technologies,
ECO Mode, Power Management
+852 9149 2164
1504191160
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