Tube Power Amp Reviews

It's going to happen very soon.—Leonard Cohen, "The Great Event"

With a parts list that includes 18 new-old-stock Black Cat capacitors, 16 vintage-style Cosmos potentiometers, two Tango chokes, one Tango power transformer, and some of the loveliest steel casework I've seen on a contemporary product, no one could accuse Noriyuki Miyajima of skimping on the build quality of his company's only power amplifier, the Miyajima Laboratory Model 2010 ($9995, footnote 1). Then again, because the 2010 is an output-transformerless (OTL) tube amplifier, Miyajima-san spent considerably less on iron than would otherwise be the case. Think of the money he saved!

The road to hell is paved with good inventions: clever ideas that appear, in hindsight, motivated more by a desire to sell clever ideas than to make musically superior products.

The DiaLogue tube amplifiers from PrimaLuna have, at their heart, a clever idea of their own: an output circuit that is user-switchable between triode operation, in which the screen grid of a tetrode or pentode power tube is defeated by means of connection to the tube's anode; and Ultralinear operation, in which the screen grid of a tetrode or pentode carries a portion of the AC music signal, supplied by a tap on the output-transformer primary, in a feedback-like effort to reduce distortion and increase power. Fans of the former often report a sweeter, more tubey sound, while fans of the latter report a tighter, more detailed, more timbrally neutral sound. Audio enthusiasts are given to reporting any number of things.

Even as the gulf narrows between the sounds of the best solid-state and the best tubed amplifiers, most listeners remain staunch members of one or the other camp. Similarly, when it comes to video displays, the plasma and liquid-crystal technologies each has its partisans, though that conflict's intensity is relatively mild, perhaps because video performance, unlike audio, is based on a mastering standard that establishes color temperature, gray-scale tracking, color points, and the like (I'm deeply in the plasma camp). But in audio, the "standard" is whatever monitoring loudspeaker and sonic balance the mastering engineer prefers, which makes somewhat questionable the pursuit of "sonic accuracy." Still, in a power amplifier, a relative lack of coloration is preferable to amps that Stereophile editor John Atkinson has characterized as "tone controls"—usually, if not exclusively, of the tubed variety.