Theta Digital Citadel monoblock amplifier

As we all know, it's the sound that counts. However, good looks enhance pride of ownership, and Theta Digital's class-AB, 400W Citadel is as handsome a monoblock as these jaded eyes have laid eyes on.

The Citadel fairly screams "buy me!" Your first enthusiastic glance will take in the bright aluminum case, standing almost a dizzying 20" high. The aluminum (a black finish is also available) clads a steel chassis and back panel. A thick, curved aluminum endcap faces the listener, with a nicely styled control panel set out slightly from the cap. Viewed from the front, it looks like an architectural element set into a high-tech building—the entrance, perhaps. Ah, Metropolis.

The endcap is polished to such a shine that it positively dazzles when any light is shone on it. The control pod (excuse me, Mr. Kubrick) has a matte finish, the two textures played off against each other with subtle elegance. Very textural.

The control surface carries a trick Standby/Operate switch that I find beautiful in execution—it makes you think about Theta every time you switch from Standby to Operate, or vice versa. That's because the solid, chromed-brass Theta logo above the LEDs is the switch in question. It has a positive, precise movement when pressed—something like the heavy, short-throw, gated manual gearbox on a '60s Ferrari—and makes a nice, confidence-inducing click when engaged: "Sir Yes Sir Switch to On position Sir!"

Under the logo-switch are three LEDs. Right to left, the first glows red in Standby mode, green in Operate. The central LED is a Thermal indicator that torches on if the Citadel's temperature exceeds preset values, and shuts it off so it can cooleth down. (For the record, this never happened during my auditioning, and I blasted the Citadels from here to kingdom come!) The left LED, which does much to explain the "Digital" in Theta's name, is the Digital Lock indicator for the soon-to-be-ready D/A board. Alas, the board wasn't ready in time to be reviewed. But when a Citadel is so equipped, this LED will first glow red, then orange when you've got a lock. And green gloweth the LED if you select an analog input.

Finally, there's an input-selector button centered below the LEDs, but it does nothing without the upgrade DAC board installed.

The Citadel has no visible heatsinks. Heat transfer—blessedly, there wasn't too much of it—is handled by a series of curved, punched-out blanks on the sides and top. The punched-out areas are filled with contemporary-looking black-metal inserts that are perforated with small circular holes to let the heat out. On the Citadel's sides are four cutouts about a third of the way up from the base—the "belt" line, where a strip of solid metal adds rigidity. Below this belt are three cutouts that more or less line up with those above, while above the belt line a fourth strake opens up a good-sized cutout for maximum thermal efficiency.

The Citadel is beautifully executed, with a subtle, handmade Aston Martin look. There's a hint of quality in its looks that wheedles its way into your consciousness. No one element seems overemphasized; everything points to a simple, elegant, unified aesthetic.

We need backup!
At the top of the Citadel's rear panel is an overhang that's—all together now—curved! A lot is going on beneath this overhang—there's a sort of Superman-in-a-phone-booth change of identity to a pro-world layout: markings and LEDs, a board expansion bay, and separate power switch and IEC mains-in for analog and digital signals. Compared with its sides and top, the Citadel's rear panel is all business.

Center top of the back panel is a perfectly sized handle, which can't hurt—each Citadel weighs 110 lbs. Below that, to the left, are one or (optionally) two sets of output binding posts for biwiring. Theta calls these unusual posts "high-contact/low-pressure." They use Cardas 9 AWG Crosslink/Teflon wire, and a custom-made Delrin/rhodium-plated output connector tightened down with a hex key—perfect for audiophiles who don't change cables at the drop of a hat. The manual contains dire warnings about overtightening these posts when using spade lugs: You don't want to feed them bent-to-hell brass spades. But give them something nice and flat and they'll make a tight surface-contact patch. It's all beautifully thought out and executed.

Theta Digital
5330 Derry Ave., Suite R
Agoura Hills, CA 91301
(818) 597-9195