One of the best-sounding power amplifiers I’ve heard in years was the Audio Research Reference 75. I’m not alone in that; it’s one of those ‘sweet spot’ amplifiers about which nobody has a bad word, including other amp-making rivals. However, the world is changing and people are downshifting; hefty pre-power combinations are giving way to smaller integrated designs, and the VSi75 perfectly reflects this.
The VSi75 could be thought of the result of what happens if you leave something like the LS17 preamp and the Reference 75 power amp in the same room, feed them a nice dinner, dim the lights, and put on a Barry White album. It’s an integrated with all the convenience of the latest generation ARC preamps (such as the green fluro display panel, five line inputs, and row of touch buttons on the front panel) with the power and circuit design of one of the best power amps out there. The only things that are missing from the line up is a phono stage, balanced input, and a balance control.
Operation is fairly straightforward; insert the two 6H30 input drivers and four KT120 power valves (if you are using the tubes supplied, they are numbered and the 6H30s are double damped with tube dampers), putting them in the appropriate valve bases as described in the manual. Turn it on (it has a 30 second mute before playing), wait 20 minutes or so for things to thermally settle down and press the bias button. Then adjust the two pairs of KT120s in turn until they all read a bias of 65mA. This should stay stable for the rest of the 2,000 hour expected lifespan of the tubes. As ARC rightly points out, if you keep the amp powered on constantly, that’s about 83 days between retubing and such action would kick you fairly and squarely in the electricity bill. You just need to give it about half an hour of warming up from cold before it’s on song. And, you can tell just how many hours your tubes have been running, because there is a display option you access from the remote. You have the option of four or eight-ohm speaker connectors, depending on your loudspeakers, but in most cases, experiment (I went for the eight ohm taps irrespective of loudspeaker used, but you may disagree). Audio Research suggests the VSi75 keeps on getting better and better over its first 600 hours of operational use; it sounds pretty damn spiffy out of the box, but it does settle in over time, too. It is supplied open chassis, with no valve cage option; remember this if your domestic life is filled with hyperactive children using your listening room as a combined race-track and judo dojo.
Essentially shedding a preamp box, replacing the preamp with a well-engineered logic circuit, and building everything into what could be thought of as a scaled down Reference 75 is an exercise in user-convenience. As I described earlier, there is a move to downshifting and downsizing. That array of additional boxes and miscellaneous gizmos are beginning to look a touch passé, now. However, there’s a thin line between ‘convenient’ and ‘compromised’, and if you get it wrong, instead of buying a nice little does-it-all box that sings, you get something that sullies the good name of the brand, both to newcomers and downshifters. Clearly this is something Audio Research took great pains to avoid in the VSi75.
As the name suggests, the VSi75 delivers 75 watts per channel thanks to the KT120s that are slowly sweeping through the Audio Research range. I used the VSi75 with several loudspeakers, from the KEF LS50 right up to Wilson Audio Duette Series 2. In terms of source, I mostly used a Townshend Audio Glastonbury player and in terms of cable, there was a whole lot of Nordost Valhalla 2 going on. Cross-check comparison amplifiers included the BMC CS2 and the Devialet 250 on the solid-state side. This list of devices is actually important to the tale, and the reason for the importance is the Devialet.