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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: Esoteric/APL Hifi UX-1/NWO 3.0GO, Yamamoto YDA-01
Preamp/Integrated: Esoteric C-03 (transistor), ModWright DM 36.5 (valves)
Amplifier: ModWright KWA-150, Ancient Audio Single Six
Speakers: ASI Tango R
Cables: Complete loom of ASI Liveline
Stands: 4 x Ikea Molger rack and butcher-block platforms with metal footers
Powerline conditioning: 2 x Walker Audio Velocitor S
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; extensive use of Acoustic System Resonators, noise filters and phase inverters
Room size: The sound platform is 3 x 4.5m with a 2-story slanted ceiling above; four steps below continue into an 8m long combined open kitchen, dining room and office, an area which widens to 5.2m with a 2.8m ceiling; the sound platform space is open to a 2nd story landing and, via spiral stair case, to a 3rd-floor studio; concrete floor, concrete and brick walls from a converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse and 2nd-story landing.
Review Component Retail: €10.000/pr + €5.000/pr for optional Super Black Boxes

Danes don't lie.
For the longest time, that was Dynaudio's catchy byline. Whereas the Bavarians of the famous motorworks picked the ultimate driving machine for their slogan, the Danes focused on telling the truth. It is after all intrinsic to the concept of high fidelity. Then Dynaudio USA dispatched the above press release. While you would grant marketeers a certain freedom of spin (slogans are supposed to be catchy and slick after all), an official business alliance between a maker famous for serious speaker loads and a valve amp firm plainly is not about spin and slick.

It's a statement about mutual respect, intent and copasetic performance. Aerials, Thiels and Dynaudios simply aren't the kind of speakers that ever were considered tailor-made for valve gear. Yet show after show Octave's Andreas Hofmann has made it a point to demonstrate his electronics into exactly such loads. If that wasn't telling enough -- and for the longest time, America paid no attention so Octave lacked any US presence -- Dynaudio's pick for their strategic alliance in this high-profile market should lay to rest the ancient argument about tubes lacking proper drive, control and linearity into such speakers. Years ago B&W chose Classé transistors. Dynaudio now went thermionic instead.

Therein surely lies a tale. But it isn't ours to tell. Still, this connection makes a thought-provoking intro into Octave's MRE-130 monos, Herr Hofmann's top offering below his very exclusive €44,000/pr Jubilee mono towers [right].

1 - power on/off | 2 - bias selector for each tube position including off

After reviewing and awarding his brilliant V-80 integrated with optional Super Black Box and the stand-alone HP500SE preamp, I wanted a pair of MRE-130s. This was based purely on the strength of this prior exposure (for a second opinion, we also have this review of the V-80). I needed drive-anything push/pull tube amps to complete my amplifier arsenal of reviewing tools. And Octave was the very best I'd heard. Andreas recommended the optional capacitance-multiplying Super Black Boxes to assure uncompromised 2-ohm stability. I trusted his recommendation and the order was written.
1 - RCA input | 2 - input selector (RCA, XLR or mute) | 3 - XLR input | 4 + 7- winged speaker terminals | 5 - multi-pin socket for optional power supply box | 6 - serial number | 8 - power IEC | 9 - international voltage and max power draw declaration

Octave history and philosophy was covered in detail in the earlier reviews. In short, Hofmann's father developed the firm as a transformer designer and supplier to medical, radio and industrial clients; Andreas expanded into hifi and valve gear yet keeps all manufacturing domestic to not outsource offshore. As Dynaudio rightly stated, Octave is adamant about comprehensive electronic protection of its output stages. They run 'artificial intelligence' to assure precision bias, strategic power management for delayed ramp-up and constant circuit monitoring and no-fault tube operation. For load invariability and performance linearity, Octave relies exclusively on push/pull circuits with pentodes and feedback. Key concerns are immunity to back EMF, phase stability, wide bandwidth and low noise.

The MRE-130s run a classic pentode rather than UL output stage. Two 6550s or KT88s parallel per phase and benefit from non-traditional additional power supplies for regulation. Driver tubes are 1 x 6C5 (an octal triode inside an outer metal casing) and 2 x ECC82 (E82CC, 12AU7A, 5814, 6189) which are anticipated to last 10 years. The power pentodes should run 3 - 5 years. All tubes are checked and play-tested by Octave to require no burn-in. Each MRE-130 measures 485 x 408 x 176mm WxDxH and weighs 22.7kg. Tube sockets are ceramic with silver contacts, the double-sided PCBs use 130u Cu traces with thru-holes and storage capacitors are of the low inductance kind. Power draw is 160 watts at idle, 320 watts at full power. Max power is 130 watts into 4 ohms (140 at 2% THD), frequency response is 10Hz to 80kHz +/- 0.5dB. There are no relays in the signal path. Feeding signal during the 2 to 3-minute warm-up cycle could pass a distorted signal but the amps are unconditionally stable unloaded. An unusual feature is the rear-mounted mute toggle. It allows cable swaps without power-down. Selectable RCA and XLR inputs are standard as are paralleled winged speaker terminals for biwiring. The optional Black and Super Black Box connect via 50cm multi-pin umbilical (longer umbilical lengths upon request) but not to the wall directly.

As the graph demonstrates (3W, 4Ω, 30Hz to 20kHz), THD always ties directly to correct bias. Curve 1 shows proper bias. Curve 2 overshoots by 10%, curve 3 by 30%. The difference of 0.2% and 4% THD between correct and pushed settings is significant. Sadly, these days very few valve amp manufacturers run fixed bias. Even though it offers higher output power and more accurate bias when properly implemented, most don't trust their customers. If those must face multi-meter probes and hard-to-reach access points, such mistrust is well placed. Auto bias thus became the default hifi solution. Yet it doesn't allow for tube monitoring. Many an upset amp has been returned for service only to be diagnosed with a faulty tube. The customer feel stupid, the manufacturer grudgingly absorbs warranty ship charges without proper cause. (Yamamoto's auto bias gets around this with a meter that shows actual bias current.)

Octave exhibit at Munich HighEnd 2009 - their V40SE integrated droves the big Dynaudio Sapphires with aplomb

For such reasons, Andreas Hofmann prefers fixed bias. To not confound owners, he has implemented an unusually precise and idiot-proof scheme with differently colored LEDs that are coupled to precision op amps. Without any tech know-how, anyone can monitor and set this bias to perfection. It's German ingenuity at work, no hard hats required. Perhaps that's another reason why Octave is big in Japan. That country is notoriously selective about its hifi imports. Hopeful parties routinely deem it the hardest market to break into. With Octave operations spanning two decades, the firm has a proven track record and its models enjoy unusual longevity within their lineup [Jubilee preamp below].

The company has shown stability and a very conservative approach both to business and in how its products require no hand holding or outré speakers to work as advertised. You could call it Tubes for Dummies and Everyman. Which still fails to justify why one should continue bothering with the archaic vacuum tube. As proud new owner of the MRE-130s monos and numerous SETs, I naturally have an opinion. But I also count amongst my review gear ModWright's massive KWA-150 all-transistor machine and Nelson Pass' FirstWatt F5. If Octave has laid the usual power/drive concerns to rest to make speaker selection no longer contingent on output devices (or vice versa), which type of properly liquid listener might gravitate to the MRE-130s over transistor behemoths?

Here's what's under the hood [image opens to full size in a new window].

Octave website