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Reviewer: Srajan Ebaen |
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Octave. It's an interesting name for this audio firm from Karlsruhe, Germany. Double any audible frequency and you get the same tone. Just an octave higher; the same yet not the same. The more you double, the more frequencies separate one octave from the next. This separation -- at once the same as in tube amps which any number of companies make; but different by living on a higher plateau -- could be an intentional play on words. Or not. But explains company president Andreas Hoffmann: "Valve models are built nowadays by any number of players. About ours, I dare say that they truly do contribute something unique to the market. For integrateds and power amplifiers, our focus is on push/pull circuits of relatively high power. The latter isn't absolutely key but absolute stability of the output stages is. Ours are exceptionally load tolerant and of high bandwidth. Indefinite extension on top isn't as vital as building out extension down low to serve proper tone colors. |
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"Accordingly, our amplifiers/integrated find themselves nearly exclusively mated to regular dynamic loudspeakers by the likes of B&W, KEF, Dynaudio, Triangle, Sonus Faber and such, all solid mainstream brands. Needless to say, I believe there are special finds among these brands too but the clients will always be limited by what their domestic market offers. Particularly in Germany, that variety is quite limited. The three stepping stones of our Octave range are quite universal and, basically, hybrid affairs. We don't use pure valve preamps since I believe certain circuit junctions are better served by transistors. In output stages, tubes will always tend to limit max current while high output impedances impose their own limitations. Hence we have developed a number of solutions to address this. |
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| "Due to their implementation, our preamps are wildly flexible and proven (the core platform of today's HP 500SE dates back to 1986). This explains why they're all fully mature designs - also sonically. Preamps thus are very important to us but sound with an expensive machine is merely one aspect. To me, long-term stability and reliability are every bit as important. Yet reliability and protection against mishaps or exceptions don't just happen. They require very deliberate optimization circuitry. Protection in low-level circuits is relatively easy to achieve but with high- | |||||||||||||||
| level signals at great amplitudes, rather more complexity is involved. All Octave amplifiers are very comprehensively safeguarded against user error and parts wear including catastrophic power tube failure. |
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"Certain audiophiles regard electronic protection circuitry with a high degree of suspicion but I believe you cannot overdo technical sophistication in these matters. With room for safety improvements comes the parallel demand to safeguard or even refine sonics while fulfilling all the legal safety regulations and requirements of the CE and VDE. This then covers our basic concept brief. For company history, we date back to my dad and 1968 when he founded the firm to produce ultrasonic amplifiers. Our main clients at the time were industrial firms involved in the domestic ultrasound sector as well as producers of high-level power supplies. Against this background, I fell into amplification and loudspeaker design and the development of valve kit. From the very beginning, my demand was to offer novel electronic solutions but to not market them until they were fully and truly mature. The requisite financial independence for that was guaranteed by our industrial accounts, something that still holds true all these many years later. |
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"What has changed is that the manufacture of valve consumer electronics has grown to become a larger part of our enterprise. It is currently led by me, with 12 employees while we also train industrial electronics applicants. Worthwhile mentioning too is that all R&D and all production occurs exclusively in-house." I next asked for a brief overview of Octave's current lineup. "For integrateds, we have the V40 at €3.300, the V70 at €4.400 and the brand-new V80 at €6.800 without phono, €7.200 with MC. In preamps, we do the HP300 MKII at €3.400 or €4.300 with MC phono. The HP500 SE linestage is €6.800, €7.800 with MM/MC phono. The top model is the Jubilee Line preamp at €22.600 [above]. For power amps, there is the 65wpc stereo RE 280 MkII at €5.200, the MRE 130 monos at €10.000/pr and the Jubilee monos at €44.000/pr [below]." |
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Which segued neatly into what to review. "I think the V80 would be of interest since it's a new model for us with special sonic qualities. Alas, it really warrants an exceptional loudspeaker. In Munich, we demoed with the Triangle Magellan Quator which I found quite promising considering that the speakers were brand new and not broken in. For our integrateds and power amps, we also offer the optional black box modules in normal and super versions. Those connect to the machines via special umbilical and significantly increase power supply capacitance to stabilize current delivery and reduce impedance. This improves dynamic range, separation, depth, soundstage size and articulation. If source and speakers are appropriate, you won't want to listen without them. At least that's been my experience even though small and lithely voiced speakers will lean out contrary to popular expectations that these supplies would fatten up fundamentals. The bass will clearly gain in definition, attack and decay but not in mass. |
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"Seeing how you're currently reviewing the Esoteric A-100, I'd opt for the V80 with Super Black Box. The V80 too sports a respectable S/N ratio of -103dB, certainly sufficient for high-sensitivity speakers. Unlike auto bias presently so en vogue (and used in our since discontinued V50), the V80 is fixed bias and relies on external precision bias trim pots and LED confirmation. I prefer this scheme because it allows the user to monitor the output bottles. With auto bias, diagnostics are impossible unless a machine is fitted with some form of status display. In the days of the V50, it wasn't uncommon to have dealers and customers return kit for repair when the only thing wrong was a defective power tube. Since we have no control over the technical know-how of dealers or end users, I opted to relinquish auto bias even if it was implemented perfectly. With the V80 (and V40 and V70), the state of the output tubes can be readily monitored and their bias corrected individually. No special knowledge or tools are required. |
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"The V80 integrated amplifier is copasetic with most currently available pentodes like KT66, KT77, KT88, EL34 and such. Up to the RE 280MkII, our power amps all adopt pentode operation which enables affordable tube rolling which many Octave owners have embraced with passion. For review, I'd also suggest the HP500 SE preamp with or without phono. The latter includes a switchable subsonic filter and is optimized for low-output cartridges with its high amplification factor. I'm currently using the Lyra Helikon. Bandwidth for the SE is a colossal 0.2Hz to 1.5MHz (2.3MHz at -6dB), S/N at max output with high gain is -96dB, with low gain -103dB. Our volume controls are embedded in the input stage which stabilizes the amount of treble rush, usually no issue. Power supply hum is essentially non-existent. The SE's power supply is external and this preamp should work fine with your various SETs. I'd be happy to make both machines available." Jawohl, Herr Hoffmann. Wo unterschreibe ich? Where do I sign? |
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The 2-stage preamp with global feedback uses a single ECC82 in the input stage and a pair of Siemens D3A/EF184 pentodes in the class A output stage. There are four RCA inputs, one tape out, two RCA preouts and one balanced output whose transformer, like all Octave iron, is wound in-house. Output impedance is 100/50-ohm for RCA/XLR. Dimensions are 435 x 147 x 393mm and 180 x 100 x 280mm W x H x D for the preamp and power supply respectively. Hi/lo gain switching (17.5dB / 9.5dB or x 7.5 / x 3) improves matching with power amps and speakers. Soft-start power management extends tube life expectancy up to a claimed 10 years and the power supply is fully regulated with Mosfets, rectified by Schottky diodes and offers a residual noise floor of 300µV. An IR remote is included and the SE version is limited to a production run of 100 units per country. |
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The HP500 SE with phono gains an additional three valves [the smaller board towards the rear panel - 1 x 12AX7/ECC83, 1 x 12AT7/ECC81, 1 x 6922/ECC88]
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| The V80's input and output tube heaters as well as its high-voltage rails are logic controlled such that current conduction of the output tubes as well as input stage voltages are constantly monitored. The entire process is supervised by Ecomode and comprehensive protection circuitry so redundant that Octave claims essentially zero failures for machines 10 - 15 years in the field (except for power tube failures which is naturally beyond their control). Scenarios that will invoke protection are overdrive (excessive levels with extreme infrasonic content); shorted loudspeaker cable under high signal; output tube failure; and low-level tube failure which would result in overdrive of the associated channel. Power consumption at idle is 160 watts due to an "exceptionally efficient power transformer with negligible losses" and a defeatable Ecomode powers down the amp after 10 minutes of inactivity. It reduces power draw to 20 watts and increases passive security but obviously doesn't allow for bias adjustments. When signal is sensed during sleep mode, the V80 resumes service after a 30-second stabilization protocol. Max power consumption is 400 watts. The regulated power supply is unconditionally stable from 210 - 250V AC. Circuit gain for the V80 is a high 38dB. |
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Tube bias calibration uses 3 LEDs (yellow, green, red) which are linked to ultra-precision operational amplifiers for a claimed 0.3% accuracy, far higher than your average multi-meter probe would be. Red signifies over bias, yellow under and green alone sufficient but inaccurate. Precision low bias for 6L6, KT66, EL34, KT77, 5881 and 6CA7 lights up both yellow and green, high precision bias for 6550, KT88, KT90, KT100 green and red (EL509/159 are not permissible). Stock tube complement is 2 x 12AX7, 1 x 12AT7/6072 and 5 x 6550s (one spare). ElectroHarmonix KT88s used to be standard but Andreas reported present QC issues with those to prefer 6550s until his Russian supplier can solve the KT88 issues. The amp also includes a three-prong power cord, remote control, a 3mm flat-blade screw driver for bias adjustments and a 2mm hex key to remove the tube cage. The V80 sports a transistor headphone socket with 10V RMS into 300-ohm, compatible with 30 - 2000 ohms cans. The amplifier can be set to be live at only the speaker outputs, only the headphone socket or both. Further flexibility comes from a relay-switched tape loop which here is called "Master Out, Master In" to allow insertion of an equalizer or operation as a fixed-gain amplifier. A variable pre-out affords subwoofing or -- perhaps in conjunction with a second V8 configured as power amplifier -- biamping. Like all Octave amplifiers, the V80 may safely be fed signal without an applied load. The Super Black Box has a special fast discharge function after power down via a monstrous load resistor which is verified with the yellow 'Unload' LED. Its stock umbilical is 50cm but longer lengths are available by request. And that about covers the basics on the brand and the two review subjects Andreas and I decided on to introduce the brand especially to US readers where Octave has never enjoyed representation yet. |
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