Theta Digital Enterprise monoblock power amplifier

Monoblock power amplifiers seem to be moving in and out of my listening room faster than green-onion salsa from Chi-Chi's. Over the past six months I've had the Parasound Halo JC-1, the Halcro dm68, the Pass XA-160, the Musical Fidelity kW, and now these 300W (into 8 ohms), $4500-each beauties from Theta Digital. All of these amps sounded as different as they looked, which was no surprise; too bad the "measures the same, sounds the same" dogmatists remain open for business.

Once upon a time, more than 15 years ago, Theta Digital was exclusively a "digital done right" company, as their slogan has it, specializing in custom, algorithm-driven, two-channel oversampling audio DACs, which were then exotic. In fact, Theta introduced the DSPre, the world's first DSP-based outboard DAC, back in 1988. (DSP stands for "digital signal processing.") Soon thereafter Theta introduced a CD transport that was actually a heavily modified laserdisc player, linked to the DSPre via an AT&T glass optical cable. These and other Theta innovations were then copied throughout the audio industry.

Theta's idea was to squeeze every last bit of performance from 16-bit/44.1kHz CDs, an agenda left me cold. To my ears, the best of what resulted from it didn't begin to approach the musicality of most modestly priced turntables. I remember arguing with Theta's Neil Sinclair about the futility of it all, but he's since built a successful company out of it. So much time has passed since then that I bet some of you don't even know what a laserdisc-based CD transport might be, or why one would want to use one to play CDs. Theta didn't release a one-box CD player until 1997.

When the home theater boom began to wax and interest in tweaky two-channel digital audio products began to wane, Theta smartly began applying its core expertise to designing modular multichannel A/V preamplifier-processors—though the company is still very active in the two-channel DAC arena. And with the first Dreadnaught in 1999, Theta began building multichannel home theater amplifiers.

Veteran designer David Reich (Dayton-Wright, Classé, McCormack) dreams up Theta's power amps, including the no-holds-barred, 400W-into-8-ohms Citadel monoblock (reviewed by Jonathan Scull in the May 2002 Stereophile). Needing some massive electronic horsepower to drive a big Aerial Acoustics 5.1-channel system for a Stereophile Guide to Home Theater review, I prevailed on Theta to lend me three fortress-like Citadels to drive the front channels. Based on that experience, when the opportunity arose to review this three-quarter-size edition of the Citadel in my two-channel system, I said yes.

No Star Trek Puns
With three-fourths the power and two-thirds the height of the Citadel, the Theta Enterprise doesn't quite have the same level of visual drama. But it's attractive enough, with its sculpted aluminum front panel and rounded chassis cover, made from a single U-shaped sheet of brushed aluminum. A vertical, remote-control-like fixture attached to the front panel contains a Standby button and LED and the Theta logo. Stereo pairs of Enterprises come with mirror-imaged front sculpting and control-panel placement. Instead of conventional external heatsinks, the amp features dramatic, carved-out openings protected by black-mesh inserts; a massive "floor-to-ceiling" heatsink assembly is hidden within.

Like the Citadel, the Enterprise is a fully balanced differential (no common grounds need apply), zero loop-feedback design featuring, according to Theta, "a 4-layer glass-epoxy circuit board: 1 layer each for positive and negative supply lines; 1 layer for ground plane; 1 layer for signal path." The Citadel and Enterprise have similar circuits—including for the bridge rectifier, main board, and capacitor bank—and use the same output devices; Theta claims they sound similar as well. While the Enterprise is rated at 300W into 8 ohms or 500W into 4 ohms, Theta says 350W and 525W, respectively, are more typical.

The rear panel is as businesslike and complex as the front panel is jewel-like. Along with RCA and XLR inputs, there's a Cardas-type binding post (footnote 1)—the kind that locks both channels' hot and ground connections with a single knurled knob—as well as both RS-232 and remote trigger facilities for home theater integration. Also on the rear panel are fuses for both positive and negative power-supply rails, an on/off switch, and an IEC jack. Three LEDs let you know when a fuse or fuses have blown or when the amp has been driven beyond its normal operating temperature—as if you won't know that when the music suddenly stops and you look up to find that your amp stand has melted. (Just kidding.)

A second Cardas binding post is optional for biwiring or biamping, or you can opt for high-pressure Reich-type connectors designed by...David Reich. This is an unusual clamping-type monolithic mechanism using two hex-head screws, but you're warned that the connector will break if you overtighten the screws, and that's not covered under the warranty. Nor are you covered if you remove the screws, then cross-thread them when you reinsert them. Making things even more chipper is that, aside from warnings about what not to do, there's not a word in the instructions about what you should do to use the Reich connectors correctly. Nor is there anything about how they actually work, and/or how best to insert your chosen cable ends into it. You just sort of stick them in these openings where the sun don't shine and hope for the best.

Ah, but I overdramatize the situation. On the other hand, the Reich connectors didn't break.

Enterprising Sound
I followed Theta's recommendation and gave the Enterprises a week's continuous use before doing any critical listening. After that week, I spent the next three listening to countless LPs, CDs, and SACDs using the single-ended Musical Fidelity kWP and Hovland HP-100 and the balanced VTL TL-7.5 preamplifiers. Toward the end of the review period, Richard Gray's Power Company did their thing to the electricity, and Aerial Acoustics installed their flagship 20T loudspeakers. In short, I heard the Enterprises in a variety of settings, some of which were more complementary to the amp's sonic character than others.

If you like your power amps on the rich and warmish side, the Enterprise probably won't be to your liking, though it will certainly gain your respect. If you like cleanness, transparency, and sonic law and order, the Enterprise will mesmerize you with clarity and definition—I could see into the soundstage for miles. It achieved its astonishing lucidity at the expense of a lush midrange, but the deficit was subtle enough to be made up for with the proper choice of complementary gear.

Playing live LPs such as Tony Bennett at Carnegie Hall or Mel Tormé and Friends Live at Marty's, I was treated to pleasing extremes of low-level, HDTV-like resolution of detail, crystalline clarity, and a giddy overload of spatial cues. Back-of-the-hall reflections seemed to ricochet and land in my lap. If I had to use my fingers to describe the initial impression this amp makes, I'd rapidly rub my index and middle fingers against my thumb.

The Enterprise's sonic character begins with lithe, harmonically rich, texturally supple, reasonably extended deep bass, though not of the iron-fisted variety you get from Krell, the Musical Fidelity kW, and some others. Both styles have their backers; some listeners find the iron-fist approach relentless and mechanical, while others consider such control beneficial for rhythmic delineation. The Enterprise was a bit lean in the midbass compared to the X-160, the Halo, and the kW, and more in tune with the Halcro dm68's lean but taut, extremely detailed, and well-defined midbass performance.

In the critical midrange, the Enterprise was ever so slightly recessed but oh, so crystal-clear and revealing—again, like the big Halcro. There was some loss of mystery and plushness, but in exchange I could hear images with pinpoint focus and extraordinary resolution of low-level detail, down into the vanishingly low noise floor. The Enterprise was a quiet amplifier.

Footnote 1: This has limited clearance; if you use spade lugs with large-diameter metal barrels, these might touch the edge of the chassis.—John Atkinson
Theta Digital
5330 Derry Ave., Suite R
Agoura Hills, CA 91301
(818) 597-9195