Balanced Audio Technology VK-600M SE Monoblock Power Amplifier

Can a massive solid-state amp deliver the immediacy and delicacy of a low-power, single-ended design?

A fundamental principle of high-end audio design holds that the signal path should be as short and simple as possible, and the power supply as elaborate and massive as practical. The VK-600M SE solid-state monoblock power amplifier from Balanced Audio Technology (BAT) takes this idea to the extreme; this amplifier has the signal-path simplicity of a low-power single-ended amp, coupled with a power supply that looks as though it could light and heat a small city. (See the accompanying interview with designer Victor Khomenko for details.)

We tend to think of an amplifier’s power supply as outside the audio signal path. After all, its job is merely to supply direct current to the tubes or transistors that actually do the work of amplifying the music signal. Looking at a schematic reinforces this view; we follow the audio signal from input to output, with the power supply represented as an adjunct to the signal-amplifying electronics.

A more accurate way of thinking of a power amplifier, however, is of a device that pulls 120V/60Hz alternating current from your wall outlet through the amplifier’s power transformer, converts the AC into direct current (DC), stores that energy in large capacitors, and then allows the tiny audio signal at the amplifier’s input to modulate the stored energy as electrical current that is driven through the loudspeakers by the power amplifier’s output transistors. This way of thinking of a power amplifier leads to the realization that an amplifier’s power supply is actually in the audio signal path. The current that ultimately drives the cones in your loudspeakers back and forth comes from the wall outlet via the amplifier’s power supply.

BAT’s emphasis on the supply’s importance is reflected both in the standard VK-600’s substantial power supply and in the upgrade path BAT makes available. The amplifier’s basic configuration is a stereo unit at $7995. Two levels of power-supply upgrade are available: the BAT PAK at $995 and the SUPER PAK at $3000. Both are boards containing rows of capacitors that beef up the power supply by adding additional energy storage. When fitted with both upgrade options, the amplifier becomes the SE version. (The SE is $11,500 when purchased initially, which saves you $500 over starting with the basic amp and upgrading.)

The next step up is the VK-600M, a monoblock version that combines the stereo amplifier’s two output channels into a more powerful single channel. BAT PAK and SUPER PAK upgrades are also available for the mono version. The ultimate realization is the fully loaded VK-600M SE reviewed here ($23,000 per pair).

Power output is rated at 300W into 8 ohms, a figure that doubles as the load impedance is halved (600W into 4 ohms). This suggests that the VK-600 can deliver power to currenthungry loudspeakers that have low-impedance dips. The two channels are completely separate (including transformers) with each supplied by its own AC power cord. Inputs are balanced only, reflecting the amplifier’s architecture of fully-differential circuitry from input to output. If you want to drive the VK- 600 with an unbalanced signal, you’ll need RCA-to-XLR adaptors, available from BAT.

This amplifier is built like a tank, with a very nice, but not overly lavish, front panel. The money went into performance rather than cosmetics.

The VK-600M SEs were in some ways revelatory, particularly when partnered with BAT’s top-of-the-line VK-51SE preamp. For starters, these amplifiers exhibited iron-fisted control over the Wilson MAXX 2’s big woofers, without the slightest hint of strain at any listening level. The VK-600M SEs didn’t just go low and play loudly; they produced a rock-solid, tight, and visceral bottom end that served as a strong tonal and rhythmic foundation for the music. Their dynamic impact, explosive transients, and effortlessness in the bass were peerless, in my experience. I’ve never heard the dynamic envelope of kick drum or tympani reproduced with such depth and startling impact, coupled with equally sudden decay. For instance, the spectacularly recorded bass and kick drum on Travis Larson Band’s Suspension [Precision] were portrayed so vividly that this high-energy power trio seemed to have much of the life and drive it has in concerts. The VK-600M SEs (along with the Wilson MAXX 2) even resolved the individual strokes of two bass drums played quickly, rather than turning the instruments into an undifferentiated low-frequency blur. Taut, muscular, and authoritative are how I’d describe the VK-600M SE’s bass. (The MAXX 2 turned out to be an ideal match for the VK- 600M SEs, since the Wilson’s superb bass took full advantage of the BAT’s bottom-end impact and resolution.) The musical result was a visceral, whole-body involvement in the music (some music, at least) that smaller-scale hi-fi systems just don’t deliver. Although I can greatly enjoy a well-chosen and set-up system of modest proportions, a playback system’s ability to deliver the bottom two octaves with unfettered dynamic contrasts is an experience unlike any other.