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S-400 Series II 400W/channel

The sound of the S-400 is extraordinary in the way it combines the power and authority you would expect from 400W per channel with delicacy, subtlety and fine detail. Perhaps the most striking quality is the way it portrays the harmonic structure, or timbre, of acoustic sounds alongside its other strengths.

The S-400 is almost like two amplifiers in one, offering on-the-fly switching between valves in tetrode mode – for the greatest power and control – and triode mode – for a gentler presentation such as for late-night listening.

Underpinning this stellar acoustic performance is some very clever micro-processor control that maintains the valves working in their optimum "envelope" at all times, under dynamic playing conditions and varying supply voltage. At switch-on there is a 4-minute countdown visible in the front window as the circuits and valves "soft start" and come slowly up to their operating points.

Valve bias and fault sensing are fully automated by the logic circuits. Valves are re-biased all the time, between music passages, to keep them working optimally and to extend their life significantly. If a valve should drop below its ideal performance the fault will show on the front display panel. The amplifier can adjust for smaller faults and carry on playing but will shut down automatically if the fault is more serious.

This level of micro-processor control helps to make the amplifier ultra-reliable in long-term use.

A removeable panel below the display gives access to diagnostic controls, including valve bias figures and valve and amplifier hours of use.

Visit the VTL site for more detail and specifications: S-400