VTL IT-85 integrated amplifier
The only wrinkle I can think of regarding the long-term value of such designs is whether or not you plan to eventually upgrade your system. Separates buyers who've already made a substantial investment in a preamp have the flexibility to substantially upgrade their power section should circumstances warrant it—say, if you're faced with the possibility of filling a much bigger room with sound, or stepping up from efficient, coherent two-way speakers to bigger, full-range, floorstanding designs that crave more current and driver control.
Enter Luke Manley, of Vacuum Tube Logic, with a clever, cost-effective, high-performance solution that's equivalent to a first-rate, remote-controlled, active line-level preamplifier—tubed, no less—with a fully functional power section thrown in for free. Do I gild the lily? In triplicate, but only to make a point: When auditioning the VTL IT-85, consumers need not feel unduly limited as they contemplate future upgrades. While the IT-85 integrated amp was designed to be a no-compromise, standalone unit, its buffered preamp output means that you can mate it to its standalone VTL sibling, the ST-85 stereo power amplifier that Lonnie Brownell reviewed for Stereophile in February 1999. The IT-85 and ST-85 were designed to form a balanced, coherent, gain-matched system with which you can horizontally biamp your speakers without any external crossovers: the ST-85 handles the low frequencies and the IT-85's power amp covers the high frequencies, even as the latter's preamp section functions as the overall system controller.
Vacuum Tube Logic makes some of the world's most impressive tube amplifiers—such as the imposing, dual-monoblock Wotan (1250Wpc tetrode, 600W triode). With its array of two dozen 6550 tubes per channel and a separate chassis for the power supply, the Wotan weighs in at...well, you don't want to know...and retails for $27,500. And, by Jiminy, he run warm—so warm that, two years ago, at HI-FI '98 in Los Angeles, when VTL used three sets of Wotans to triamp Christopher Hansen's MartinLogan/Wadia showcase system (it won best sound at the Show), they were compelled to install a huge bank of noisy fans to avoid thermal Armageddon. (To run the demo, they had to turn off the fans and close the doors. The heat inclined me toward Morpheus; I was beginning to snore when Stereophile webmaster Jon Iverson elbowed me sharply in the ribs.)
Considerably reduced in scale and using but a single pair of Svetlana EL34s per channel, the IT-85 confers the sound signature of its beefier brethren for a fraction of the price: $2500 for the IT-85, and $1750 more should you invoke the biamping option by purchasing the matching ST-85. This combo generates significantly less heat than the mighty Wotans; nevertheless, VTL designer and honcho Luke Manley warms to the subject of his aural double-decker with no less enthusiasm:
"The circuit topology on all of our amps—the input stage, phase splitter, and push-pull output stage—is the same throughout the whole range," Manley explains by way of illustrating the trickle of technology down to his newest product. "We just add more power supply and more tubes for more power. But it gives a family sound so when people upgrade their systems or go to higher power, they know what to expect." And while readily acknowledges that "it's a given that you get multiple sonic improvements with separates," Manley makes a compelling case for the efficacy of his first integrated design.
"In our mind, the IT-85 was for people who wanted the performance of separates but who wanted only one box, and who didn't want to remember which one you turn on first and last and all that. Sure, in some of our top-of-the-line power amps we go so far as to employ two separate chassis to isolate the power supply from the output stage, for obvious reasons. And I'd say that running with a separate preamp would tend to produce a somewhat smoother sound, with better transparency and dynamics. However, there are some sonic advantages to an integrated design. For instance, no matter how transparent your buffer is, having no buffer is always better—much clearer and more transparent. However, when you're designing a standalone preamp and the amplifier is not known, you've got to put a buffer on there because you cannot assume that the guy is going to always use short interconnects and a tube amp with high input impedance. On the IT-85, because the amp is known and it's right there, we were able to use the gain stage of our VTL 2.5 preamp—the first two 12AU7 tubes in the front—and we didn't need the buffer. The IT-85's pre-out is cathode-follower-buffered, though, because we knew that sometimes it might be employed to drive a solid-state amplified subwoofer."