Integrated Amp Reviews

When I receive a product sample for review, I look forward to taking photos while I unpack the thing, as a guide to repacking for later on. This company provided an illustrated packing list—it was the first thing I saw on slitting open the carton. I look forward to crafting amusing remarks about poorly written or whimsically translated owner's manuals; this company provided the clearest, most comprehensive manual I've ever seen. I look forward to having some sort of anomalous event—smoke, noise, or smoke and noise—to write about. This product offered nothing of the sort.

The company in question is Germany's Octave Audio, and the sample they provided was of their entry-level integrated amplifier, the V 40 SE Line ($5300)—a remarkably well-built, well-presented, reliable, effective, mature, professional product. Damn it.

Description
The company known today as Octave Audio has its origins in the Hofmann transformer-winding company, started in 1968 by Karl-Heinz Hofmann, whose son Andreas Hofmann has been designing and building amplifiers since the 1970s. By the 1980s, the products of Hofmann the Younger began to set the direction for a manufacturing effort that soon began doing business under its present name.

The Octave V 40 SE Line is a true integrated amplifier, with an active preamplifier section that uses one 12AX7 dual-triode tube and one 6922 dual-triode tube, for phase inversion—its model designation notwithstanding, the V 40 SE is a push-pull design—and for line-level gain, the latter measuring 14dB at the V 40 SE's preamp-out jacks. The capacitor-coupled output section, which adds another 38dB of gain, uses one pair per channel of beam-power pentode tubes; KT88s are supplied as standard, although the owner's manual suggests that the owner can also use KT90, KT100, or 6550 tubes. Other allowable tubes include the 6L6, KT66, KT77, 5881, or EL34 pentodes, although the user is cautioned that none of the tubes in that latter group will provide the full 40Wpc for which the Octave amplifier is specified. Whichever the choice, output tubes are operated as pentodes, with up to 300V on their screen grids, and the output circuit uses 10dB of global negative feedback.

The Octave V 40 SE has a fixed-bias output section, with output-tube cathodes close to ground and adjustable bias current on the signal grids. Along with a protection system that monitors and regulates the rail and heater voltages, and a user-defeatable Ecomode system that reduces those same voltages when the amp is powered up but not in use, the V 40 SE incorporates a system that both monitors output-tube bias currents and gives even the most technophobic user an easy means of adjusting them, as needed. (I'll come back to this feature in a moment.) Unsurprisingly for a product with such sophisticated circuitry, the Octave is among those contemporary tube amps that also contain a number of solid-state devices, including four op-amps, numerous regulators, a few bipolar transistors, and, of course, full-wave rectifiers for the power supply.

The V 40 SE's case is mostly of aluminum alloy, with panels that fit together solidly and precisely. The first things one sees on removing the top cover are the generously sized output transformers and mains transformer; the latter is almost startlingly impressive, its wrappings appearing to rise from a pool of translucent potting, in the manner of Millais's Ophelia rising from the brook. Most of the amp's audio circuitry is built onto a single, sturdy PCB, with auxiliary boards for power-supply circuitry, input-selector relays, and the logic circuitry that enables the amp's metal-clad remote handset. (The remote controls only volume, by means of a motorized analog potentiometer.) Parts quality is fine throughout, with new tubes from Sovtek (small-signal triodes) and Electro-Harmonix (beam-power pentodes).

Although the V 40 SE's internal power supply is hardly anemic—I spied four 400V, 470µF caps tucked between the mains transformer and the left-channel output transformer—Octave Audio also offers an upgrade, the Black Box ($1200). This outboard bank of reservoir caps is user installable: You simply first power down the amp and disconnect it from the wall AC current—a point stressed by a warning label on the rear panel—then connect the Black Box by means of a four-conductor umbilical before powering up again.

Setup and installation
I used the Octave V 40 SE in my usual system, in place of my Shindo Masseto preamplifier and Shindo Corton-Charlemagne monoblocks. Given that the Octave lacks a phono stage, I used it in tandem with my lingering review sample of Sutherland Engineering's fine Insight phono preamplifier ($1400).

Installation was straightforward for the V 40 SE, which is of a reasonable size and weight. Gold-plated RCA jacks are supplied for four line-level sources, with an extra pair of inputs, unattenuated, for the two front channels of a home-theater installation, for those who think young; preamp-out and record-out jacks also appear on the rear panel. Loudspeaker terminals are of a sort I'd never seen before, with luxuriantly large knobs that would, I assume, make it easier than usual for owners to tightly clamp their spade lugs; I carried on with banana plugs, which, perversely, I nonetheless prefer.

Not only have I never seen a better owner's manual than that which accompanied the V 40 SE: I have never encountered a surer, safer, less ambiguous, or altogether better means of checking and adjusting tube bias. On the front panel are three rows of four LEDs each, these corresponding with the four output tubes. The user begins by setting the input selector to a dedicated bias-adjust position—the amp needn't be connected to sources or speakers—then powers up the amp. Initially, under most circumstances, the bottommost row of bias LEDs—yellow lights signifying low bias current—are illuminated. Ideally, and typically, as the amp reaches normal operating temperatures, the yellow LEDs fade out while the row of green LEDs above them—signifying correct bias—begin to fade in. (This was fascinating to watch.) After five minutes, with standard output tubes in place, only the green LEDs should be lit—but if any of the red LEDs in the top row light up, the user knows to back off the current for that tube by inserting the supplied miniature screwdriver into one of four tiny openings hidden on the front display. Needless to say, if the yellow LED for a given tube remains on, the user should increase current until all is good and green again.

As it turned out, my review sample arrived in a state of perfect adjustment, again sapping my fun. Damn it.

Apart from the above-mentioned pots for the bias-adjustment system, user controls are thin on the ground. On the rear panel, a small three-position toggle is provided for defeating the above-mentioned Ecomode—as must be done during bias adjustment—and for turning off the output stage. At the front of the left side panel is a simple, hefty rocker switch for power; on the left side of the faceplate is a generously sized input-selector switch, matched on the right by an identically sized volume knob. The V 40 SE's balance is not adjustable, and a mono switch is not provided.

A nicely styled tube cage, made from very light alloy, is supplied, and Octave strongly recommends leaving it in place whenever the amp is in use. (Removing it is a simple matter of loosening two bolts with a supplied Allen wrench.) I thought the V 40 SE sounded very slightly better without the cage and so, also perversely, I left it off.

Listening
The Octave V 40 SE was characterized by an up-front sound with nonetheless excellent stage depth with stereo recordings—and with a better-than-average sense of scale. It was enjoyably vivid, even if tone/tonal/timbral colors weren't as saturated as with the best preamps and amps. And while I wouldn't describe the V 40 SE as sounding bright, its treble was sufficiently extended that reasonable care should be taken in the setup and adjusting of partnering gear, especially phono cartridges; ratty-sounding digital gear should be avoided altogether.