Smart Devices 2X150VT power amplifier
By Michael Fremer   •   January, 2002 If your audiophile habit goes back more than a couple of decades, you're probably doing a double take looking at the Smart Devices 2X150VT. Looks like a Hafler DH-200, doesn't it? That's because, at its core, a Hafler DH-200 is exactly what it is. Smart Devices doesn't name names in its brochure, but they do say that "You may recognize this amplifier as one of the dominant premium performers of the 1970s and '80s"—a reasonable enough description of the MOSFET-output DH-200, which combined outstanding sound with a very reasonable price—especially if you built the kit.

Smart then throws credibility overboard: "The world's finest-sounding amplifier is back...improved!" Was the Hafler DH-200 ever considered "the world's finest-sounding amplifier"? I don't think so! But to make doubly sure that you don't think the 2X150VT is merely a slightly modified DH-200, Smart also calls it a "stainless-steel Stradivarius."

I recognized the 2X150VT's antecedent, and you may have as well, but obviously some audio reviewers didn't. While perusing Smart Devices' website for background information after completing my listening, I was tempted by links to some reviews.

I was amazed by what I didn't read. Neither of the reviews even mentioned the Hafler connection (David Hafler, of course, founded Dynaco, another venerable name in audio.) One said the amp was based on an earlier Smart Devices design, but the other said nothing, despite the brochure's admission. You'd think a reviewer would at least be curious to know the "dominant premium performer" origin of the product being reviewed.

Now, I've owned a Hafler DH-200 since 1979 or thereabouts—the question is, was Smart Devices was smart to resurrect and improve on the ultra-popular DH-200. Conceptually, the answer is "Yes"—the 200 was a fine-sounding 100Wpc MOSFET amp. Tweakers like me were able to improve its sound by replacing its cheap capacitors and bypassing some electrolytics. Mods abound; if you do a Web search on "Hafler DH-200," you'll find plenty. Think what a real audio company might be able to accomplish with it while saving a bundle on startup tooling.

The Smart redesign
Georgia-based Smart Devices has been making professional audio electronics for 23 years, mostly for movie theaters around the world. According to their website, the company offers "over 120 specialized products for cinema playback." So this isn't about a guy in a garage buying a bunch of old DH-200s and retrofitting them with better parts. Smart licensed patented circuitry held by engineer Peter Hochstein, and obviously was either able to get inventory of "new old stock" chassis parts, or have them fabricated to the original specs.

Because the DH-200 was available as a kit, a neat, modular design was essential, and Smart has carried it forward essentially unchanged in the 2X150VT. There are two identical heatsink modules, one attached to either side of the chassis and containing three pairs of matched MOSFET devices, and a main circuit board. (The lower-powered, 100Wpc DH-200 used two pairs of MOSFETs per channel, though there was room, and even holes, for a third pair.)

Smart Devices claims to have improved the DH-200's original circuitry and replaced high-tolerance parts with precision low-noise resistors and sonically superior capacitors. DH-200 veterans will note the much-improved power supply. A large toroidal transformer made by Smart is centered between the amplifier modules, as are the large (22,000µF) power-supply caps. These caps are topped by a circuit board containing rectification, the rest of the power supply, and the bridging circuitry.