Mastersound 300 B S.E. integrated amplifier
By Art Dudley   •   February, 2008 Although she'll deny it, my wife thinks ill of me because I've failed to buy her a new Mini Cooper. I can point to a number of things in my defense—especially the Mini's lack of all-wheel drive, which we need for climbing our quarter-mile driveway in bad weather, and its insufficient cargo and passenger space—all of which would constrain a Dudley-owned Mini Cooper to recreational use only. And a new round of car payments would be difficult to justify for those reasons: not because I'm cheap, and not because I'm too old to appreciate a car that's fun to drive.

I admire the new Mini. Steeped as it is in the engineering tradition for which BMW, its new parent manufacturer, is rightly famous, the latest Mini has a torquey motor, a crisply precise shifter, a pleasant interior, and a very high level of fit and finish overall—none of which could be said about the Mini's earlier incarnations (footnote 1). That's because none of the manufacturers previously associated with the Mini seemed to think that building a very-high-quality version of the thing and pricing it accordingly would meet with success. And indeed, 40 years ago, that may have been true.

The thing is, the modern Mini is cut from the same cloth as virtually any modern single-ended amp, including the Mastersound 300 B S.E. integrated amplifier. The Mastersound's output architecture can trace its roots all the way back to the very first electric amplifiers, yet its implementation of that architecture is decidedly modern.

In truth, the sorts of single-ended-triode (SET) amplifiers that we know and love today could have existed when the passenger pigeon and Lee DeForest walked the earth. But back then, no one dared dream of a commercially (let alone domestically) acceptable product built with the huge, high-quality output transformers needed for full-range operation. In the years since, we've learned that audio enthusiasts are more willing than most to buy all sorts of crazy things; big, expensive amps are just the tip of the iceberg.

Mastersound, a family-owned company located near the Italian city of Vicenza, seems poised to take advantage of that shift in the consumer cosmos. Founder Cesare Sanavio, who built his first tube amplifier back in 1947, dedicated most of his professional life to the design and manufacture of very-high-quality audio-frequency transformers. His audio-enthusiast sons, Luciano and Lorenzo, witnessed the birth of the modern SET movement, and realized that they were in a uniquely good position to join the industry themselves: rather like developing an interest in making furniture, then discovering that your family owns a sawmill. Mastersound's first commercial amplifiers appeared in 1993, and the rest, as they say, is history.

Description
The Mastersound 300 B S.E. is a true integrated amplifier, with an active line-level preamplifier in front of its final (as they say in Italy) amplifier. The preamplifier uses both halves of a single 12AU7 dual-triode tube per channel, purely for voltage gain. The driver stage of the final amplifier comprises both halves of a 5687 dual-triode capacitively coupled to the 300B output triode, which itself is operated in cathode-bias mode. (I measured the rail voltage at a seemingly high 500V, but the cathode-bias arrangement considerably lessens the operating voltage actually seen across the tube.) The output tubes are heated with DC, evidenced by the 300 B S.E.'s absence of hum through my speakers: The only unwanted noise emitted by my review sample was a brief, soft buzz, audible only when the power-supply capacitors were charging up.

The build quality is superb, and strikingly reminiscent of the Lamm ML2.1 monoblock ($29,990/pair). Most of the parts reside on a single, large circuit board, with various other bits rigidly fastened to the chassis itself. In another Lammian touch, all transformers are thoroughly potted in epoxy, or something like it. Signal capacitors are mostly polypropylene types, evidently custom-made for Mastersound.

The front panel of the 300 B S.E. sports only two controls: a volume knob and a rotary selector switch, for choosing among the four line-level inputs. A fifth choice, labeled Direct, activates a pair of inputs that bypass the Mastersound's volume pot and line-level gain stage altogether, for use with an external line-out preamplifier. (Because the disappointing owner's manual doesn't say otherwise, I first assumed that Direct indicated a line-level input from which some unnecessary parts had been removed, and that I would hear something wonderful if I used those inputs for my CD player. My family was in the next room at the time; they're still angry with me for the deafening loudness that resulted.) Source input impedances are all specified as 100k ohms, while Mastersound claims that the inputs for the power amp are closer to 50k ohms.

The remote handset supplied with the 300 B S.E. is the height of simplicity and elegance. It functions only as a volume control, and sports just two buttons: one up, one down. There are no words, numbers, or markings of any sort—the two buttons are closer to one end than the other, so you can easily tell at a glance which one is up and which is down—and, best of all, it's carved from solid wood, with a light oil finish. If I were expecting visitors, especially female visitors, the Mastersound handset is the only one in the house that I would neither hide nor throw away.

I tried without success to remove the 300 B S.E.'s tube cage. For one thing, I was curious to hear if the Mastersound's audible performance would change with different output tubes. (I have other 300Bs on hand.) For another, experience tells me that some tube amps sound better with the tubes uncovered—although I'm darned if I know why. In any event, I failed, because I lack a screwdriver with a shaft sufficiently long and thin to reach the screw heads tucked inside the corners of the cage. Caveat tinkeror.

Installation
For the most part, I used the Mastersound 300 B S.E. in my main system, where it drove a pair of Audio Note AN-E SPe/HE loudspeakers. Most of that time was spent using the Mastersound as an integrated amp, driven only by a line-level source. I also devoted some listening time to using the 300 B S.E. as a power amp only, driven by my Shindo Masseto preamp (output impedance: 600 ohms) and fed by line-level and phono sources. Although the latter was more musically satisfying overall, the Mastersound's character remained the same in both arrangements.

---

Footnote 1: I don't doubt that this observation will be met with a few howls of indignation. I'll take pleasure in knowing that most such responses will come from men who can no longer wedge themselves into the car they would defend.