Srajan Ebaen
Financial interests: click here
Sources: 27" iMac with 5K Retina display, 4GHz quad-core engine with 4.4GHz turbo boost, 3TB Fusion Drive, 16GB SDRAM, OSX Yosemite, PureMusic 3.01, Tidal & Qobuz lossless streaming, COS Engineering D1, AURALiC Vega, Aqua Hifi Formula, Fore Audio DAISy 1, Apple iPod Classic 160GB (AIFF), Astell& Kern AK100 modified by Red Wine Audio, Cambridge Audio iD100, Pro-Ject Dock Box S Digital, Pure i20, Questyle QP1R, Metrum Acoustics Adagio [on review]
Preamplifier: Nagra Jazz, Esoteric C-03, Vinnie Rossi LIO (AVC module), COS Engineering D1, Wyred4Sound STP-SE II, Metrum Acoustics Adagio [on review]
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1, F5, F6, F7; Crayon Audio CFA-1.2; Goldmund Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics UP SE NC500MB; AURALiC Merak [on loan]; ]
Loudspeakers: Albedo Audio Aptica; EnigmAcoustics Mythology 1; Sounddeco Sigma 2; soundkaos Wave 40; Boenicke Audio W5se; Zu Audio Druid V & Submission; German Physiks HRS-120; Eversound Essence; Rethm Bhaava [on loan]
Cables: Complete loom of Zu Event; KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Arkana Research XLR/RCA and speaker cables [on loan]; Sablon Audio Petit Corona power cords [on loan], Black Cat Cable redlevel Lupo
Power delivery: Vibex Granada/Alhambra on all components, 5m cords to amp/s + sub
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands [on loan]
Sundry accessories: Acoustic System resonators
Room: Rectangular 5.5 x 15m open floor plan with two-storey gabled ceiling, wood-sleeved steel trusses and stone-over-concrete flooring
Review component retail: $14'000 for HP700 with tone control module, add €930 for balanced input; €8'500 for RE320, add €2'500 for Super Black Box

An octave includes all musically relevant tones,
be it the Western well-tempered scale or the Middle-Eastern quarter-tone system. Beyond an octave, it's all repetition at either twice or half the frequencies; ad infinitum in either direction or in our case, to the limits of our human hearing. When a hifi company calls itself Octave—no 'audio, 'lab' or 'sound' required—it tells us a lot. "The name's Octave; just Octave." Where's Sean Connery when you need him most?

Our hifi provocateur turns it up to chromatissimo glissando with the modular HP700 full-function preamplifier. Be it MM or MC phono, true balanced inputs with inhouse-wound transformers, a choice of standard or 47-position stepped attenuator, RCA/XLR outputs, balance and precision tone controls - this beast with outboard power supply can be configured to do it. Being Octavian naturally means valves. That's what this German electronics house has always been about.

As the opening shot suggests—replace Focal speakers with Triangle, Dynaudio or other real-world loads—Octave gear needs no mollycoddling to perform. From that the thinking reader immediately suspects push/pull pentode or tetrode amplifiers and would be correct. Just so, boss Andreas Hofmann isn't ignorant of SET's market share.

"The High End 2016 show in Munich was more or less business as usual. For us this year will be more interesting as we'll demonstrate the new Miniwatt single-ended integrated amp. This combines a 'normal' 10wpc SET plus headphone amp but I'm running KT88 or KT120 outputs. For a year now I've been working on 300B and tetrode SE designs."

It goes without saying that the reasons why Herr Hofmann's engineering brain is unusually 'allergic' to traditional SE amps is their high output impedance, high THD, low power and higher noise floor. He dislikes high distortion and faulty compromised drive. As someone who believes in unimpeachable measurements plus the ability to play speakers of normal or even low efficiency at high levels without resorting to girls and guitars, the entire zero-feedback SET mystique is still foreign to him. But requests from foreign distributors have him investigate whether the breed can be elevated to Octave's stamp of approval.

In general then, one might think of Octave as Germany's VTL: tube gear modernized for the 21st century, its loudspeakers and our bass-heavy music. It's not about the vintage Quad aesthetic.

[In the right drawing, the switch between the output tube type selectors can change the impedance on the two RCA outputs from 100Ω to 300Ω. The factory default setting is 'low'. The fixed XLR value is 150Ω. On further adjustments, one of the XLR or RCA inputs can be set to home-theater bypass for seamless integration into a multi-channel setup.]

Back to the HP700, three selectable gain settings are high at x 18.5/25dB, medium at x 7.8/18dB and low at x 4/12dB. Bandwidth for high gain is 10Hz-200kHz -0.7dB or 0.7MHz @ -6dB. For medium gain, it's 10Hz-200kHz @ -0.3dB or 1.2MHz @ -6dB. For low gain, it's 10Hz-200kHz -0.2dB or 2.1MHz @ -6dB. THD at all gain levels is a low 0.01%/3V/10kΩ. SN/R is -98dB or 38µV for high, -104dB or 18µV for medium and -110dB or 8µV for low gain, all at 3V out. Input Ω is 50kΩ. The external power supply includes multiple shielded toroidal transformers and incorporates an AC mains filter.

To condense the essentials: mega bandwidth meets low distortion and low output impedance just as you'd expect from a modern preamplifier regardless of gain devices. Herr Hofmann takes particular pride in the linearity of his circuit including the optional balance and tone controls. A click to this page shows why.

With such figures, the still thinking reader suspects transistor buffers which factor on the XLR output to feed the balancing transformers. The RCA outputs assisted by transistor current sources couple via elite foil capacitors to Mullard EF184 pentodes though Siemens D3A* work as well. Both types saw MHz television amplifier duty during the middle of the last century. The driver for the output glass is one ECC82 double triode. The high voltage supply runs low-noise power transistors smoothed by a quad of 1'500µF Siemens caps. The phono module which this digiphile didn't ask for operates three additional dual triodes for RIAA equalization and gain.**

More capacitive filtering applies to diverse secondary voltage feeds and the Octave-wound power transformer is potted to minimize stray radiation. A metal remote pets just volume. In modern parlance, the HP700 is an end-of-life product; an aspirational effort; a luxurious proposition for the been-there-done-that customer. Even when reviewers can't afford half the gear they're so clearly privileged to host over the short term, it's always titillating to learn how the other half lives.

To said end, Herr Hofmann suggested that I add their RE320 stereo amp with optional Super Black Box or SBB for short, a massive capacitive upgrade to optimize low-impedance drive and current.

* Other plug-in alternates for the D3 bias setting are the E180F, E280F and E282F pentodes.

** "In the published photos of the open HP700, you see only five tubes because the phono input tube is hidden beneath the left grey side panel. This tube is located near the red array of small caps. You will see only a small part of the tube socket. In case of the optional control module, there is an additional tube as part of the tone control circuit but this tube is hidden under the tone control plate and you cannot see it. Of course it's possible to replace this tube without dismantling the control module."