Mesa Tigris integrated amplifier By Chip Stern   •   August, 1999 Obviously, no one wants to listen to exaggerated bass, italicized highs, or colored mids. But if you (as I have in the past few months) plug in several high-quality integrated amplifiers, each designed to a different price point, into the same basic signal chain, you'll experience a wide disparity of sound signatures.

But isn't sonic neutrality supposed to represent the ultimate measure of the designer's art? Though high-end designers may, by and large, have abandoned tone controls, the manner in which each of us perceives tonal quality cuts to the heart of the issue of individual audiophile taste. And while all roads ultimately incline toward generally-agreed-upon notions of fidelity and musicality, the interpretive license each designer brings to the creative process contributes a certain subjective element of sonic perspective that gives each of these integrated amps its particular spiritual zest—that singular element of, dare we say, personality. Which is why, in evaluating any high-end component, I can think of no characterization that so damns with faint praise as "polite." But "polite" as in what? Refined? Accurate? Neutral? Or just plain boring?

Tone, Tone on the Range
No one will ever accuse Mesa Engineering's Randall Smith of being overly polite. An innovator in the field of tube technology with numerous patents to his name, Smith developed Tandem State Imaging, in which the best attributes of triode and pentode power are combined on the fly, along with increments of negative feedback, to allow listeners to fine-tune tonal contour and sonic perspective.

During the empirical process that led to the final version of his Mesa Baron power amplifier (reviewed in Stereophile in January 1997), Smith allowed himself to be guided by audiophile notions of sonic neutrality. In distilling all of his experiences down to the final design parameters for a new, affordably priced, pure–class-A, push-pull, cathode-biased, dual-monoblock integrated amp he dubbed the Mesa Tigris, Smith allowed himself to be guided more by his own sonic intuitions, and by his sense of what was practical and germane to music lovers.

"To me, the Baron was more amp than most people really needed," he says. "I wanted an amp that could play loud yet sound effortless, where you can listen to everything and discern all of the individual elements separately and distinctly, but the blend isn't sacrificed. Maybe that's a listening characteristic I've developed from so many hours of evaluation in the audition process. Some things will sound lush and warm, but the individual instruments will be difficult to pick out. On the other hand, you can get stuff that really sounds accurate, yet it comes across as kind of sterile. I wanted an amp that offered flexibility in terms of both system and source matching, because a lot of this stuff—too bright, too lush, too forward, too laid-back, too polite, too exciting, too whatever—is like food. Depending on your tastes, some people would say that this is too bland, while for someone else it's too spicy—which is why they put salt and pepper shakers on the table. With Tandem State Imaging you can get it so you can listen to it either way you want and do the trick with your mind."

Multiple-Personality Poster Amp
Save for using a single AC power cord, switch, and fuse, the Tigris is built as a dual monoblock, with its active line stage employing a pair of 12AX7 tubes per channel. As for its power section, the Tigris is the only audiophile amp I know of that uses two different types of output tubes—four EL84s and two 6V6s per channel—operating in two different classes of power through a common transformer. The EL84 tends to be fast and musical, with a sparkling high end and a sweet, airy midrange. However, it's somewhat lacking in low-end heft, and when pushed too hard evinces a harsh edge. On the other hand, the 6V6 has a big, round, warm low end, with a lush quality in the presence region of the midrange, but tends to get tubby and indistinct when pushed to its limit. (In guitar amps, when pushed into clipping, the EL84 tends to snarl, whereas the 6V6 growls.)

When all six of the Tigris' power tubes are operating in pentode mode, total output is 35W. In two-thirds-triode/one-third-pentode, the inner duo of EL84s runs in pentode, while the outer quartet of EL84s and 6V6s runs in triode, for a total output of 20W. And in two-thirds-pentode/one-third-triode, the inner duo of EL84s runs in triode while the outer quartet of EL84s and 6V6s runs in pentode, for 28W total output. Such unique power-tube miscegenation is musically complementary: each tube type contributes precisely what the other lacks. And by running them in pure push-pull class-A, the Tigris' dynamic headroom belies its actual power-output rating with a smooth, open sound that is intoxicatingly pure and sweet. In addition, a knob on the Tigris' rear connector bay allows you to dial in three different levels of loop negative feedback, labeled Stage I through Stage III. The greater the level of negative feedback, the lower the amp's output impedance, thus allowing you to increase the Tigris' damping factor for tighter bass, smoother highs, and enhanced dynamic headroom at "Turn that thing down!" output levels.

Better yet, a toggle switch on the rear bay allows you to defeat the speaker output and convert the Tigris into a superb dedicated headphone amp. Smith eschewed cheesy op-amps and integrated circuits for a headphone tap that derives its signal from the output of the power amplifier and the output transformers—just as your speakers do. You can thus enjoy all the sonic parameters of Tandem State Imaging with your headphones, for a remarkable level of intimacy, ambience, imaging, and timbral detail that compares favorably with all but the most costly esoteric electrostatic systems.

The Tigris is a phase-inverted design; the center ground/common post accommodates the "hot" output with an 8 ohm tap to the left and a 4 ohm tap tot the right. These gold-plated, vertically mounted (thank you) four-way speaker binding posts are as good as they come. Ditto the six sets of hefty, gold-plated RCA connectors below them on the rear panel, along with the IEC inlet for a detachable power cord. The line-level inputs comprise, from right to left: Record Out, Tape In, CD In, Aux In, Aux 2 In, and Preamp Out. The last, like the headphone tap, is really the amp's final output signal: rather than being a true preamp signal (which inverts, just like the speaker outputs), it's padded down through a load resistor and allows you to control a powered subwoofer, a surround-sound processor, or another power amp in a horizontal biamping scheme. You set the Preamp Out level through the use of the rotary Volume control (mounted on the right front panel), and the Preamp Out Level Set attenuator knob (on the rear bay).

The Tigris' build is beefy throughout: the transformers are mounted on rubber iso-shocks, and one three-position, 12-terminal switch per channel handles the triode/pentode switching. On the front of the chassis are four tiny switches: AC Mains, two Power Selects to implement the three levels of Tandem State Imaging, and Audio Ground to choose between coupled or isolated positions. Two Warm/Operate switches reduce the power supply rail voltage to idle when you don't wish to power down completely.

A Veritable Aural Parfait
In evaluating the Tigris' varied sound signatures, one hardly knows where to begin—from purring kitten to roaring mama lion, the Tigris behaves like the multiple-personality poster amp for high-end audio.