The S-400 is as "high tech" as any tube poweramp can be. Designed from the onset as a tube power amp that you can just plug and play, the S-400 is something of a "smart" tube amp. It biases for you (which is a huge bonus when you buy tubes that are not quad matched or sextet matched etc) when the tubes are installed, monitors the tubes as it is being used and warns you if any tubes are faulty or needs to be replaced. If it senses an issue, it shuts down to safeguard itself until the bad tube is replaced. The amp also monitors heat level and any variation in the power supply that can be detrimental to it where it will also safely shut down to protect itself. It even has a RS-232 outlet on the rear panel where you can hook up your computer to it and monitor all the data you gather from inside the amp. In terms of tube complement, it uses two 12AT7, two 6350 and twelve 6550C (or KT-88) tubes. It will produce 300W in 8 ohms and 400W in 4 ohms in tetrode mode and 150W in 8 ohm and 200W in 4 ohm when used in triode mode. These are serious power numbers and will easily drive any speakers out there. The only thing in VTL's lineup that is even better than the S-400 are the Siegfried monoblocks which are essentially the S-400 x2 plus 650W per channel and priced three times as much at $65,000 for the pair. For the money though, we would stick to the S-400. At one third the price of the Siegfried's, they are a benchmark setting, reference tube amp. You never get a sense that the S-400 would run out of steam with the many speakers we had it hooked up with. The transparency, neutrality and openness in sound are simply top of the game for amps in the $20,000-$30,000 category. Compared to the McIntosh MC2301, the S-400 had a slight variation in warmth but had more punch in the bass, better dynamics and cleaner detail presentations. You probably won't take long to hear that this is no other tube amp and concur it is either the finest tube amp you have ever heard or at least one of the best there is.
To achieve all these greatness, the S-400 is one massive amp. Standing 24" tall, 24" deep and about 12" wide, it weighs in at a back breaking 220 lbs (or about 330 lbs shipped in its crate). The twelve 6550C tubes were recently replaced by its previous owner at the expense of more than a $1,000 for them and have only 50-60 hours them. The amp looks really good cosmetically with minor scuff marks here and there. We have the original manual and crate and would prefer a local pickup but if shipping is required, it will ship freight.