Product Detail

VTL S-400 Power Amplifier

Quick Overview
The newest addition to our Reference line, the S-400 Reference Stereo Amplifier adapts the outstanding technical achievement of Siegfried to a single-chassis stereo design. At 400 watts per channel, the...


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The newest addition to our Reference line, the S-400 Reference Stereo Amplifier adapts the outstanding technical achievement of Siegfried to a single-chassis stereo design. At 400 watts per channel, the S-400 packs plenty of power for the most demanding musical passages while retaining a remarkable ability to resolve the finest details. With the same precision-regulated power supply and highest quality components as the monoblocks, users can expect a fast, articulate and unusually vivid sound that comes very near to that of Siegfried.

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The luxurious looks, “smart” functionality and user-friendliness of Siegfried are duplicated in the S-400. Convenience features include:

  • Automatic bias adjustment - the amplifier always maintains optimum bias without user tweaking.
  • Automatic fault sensing - front panel display shows if a tube needs to be changed or if an internal fault occurs in the amplifier.
  • On-board diagnostics - all operating parameters are displayed on the front panel readout.
  • Tetrode/triode switching - accomplished with a touch of the “mode” button on the front panel.
  • RS-232 interface – all diagnostic functions can be controlled remotely via the amplifier’s RS-232 interface, enabling easy integration with modern home theater systems. User can query the status of the amplifier and run all the diagnostics remotely by entering commands on a PC via the Hyperterminal window.

While the technical facility of the S-400 makes it virtually foolproof, ultimately, it is the surprising sound that will make you a believer. Like Siegfried, the S-400 reveals the inner details and overtones of music, which results in a much more lifelike experience. Live music’s harmonic complexity and richness is fully revealed without a trace of harshness or electronic edginess.

Most listeners have traditionally agreed that the various types of amplifiers available—tube, solid state, single-ended triode, push-pull—each possess characteristic strengths and weaknesses. The advanced engineering of the S-400 succeeds in extracting the best qualities of each of these designs into one unit. The immense power reserves provide a foundation for music on the level of the best solid state amplifiers; the warmth, agility, and rich timbral presentation of the midrange recalls the best of single-ended triode designs, yet the S-400 remains completely unfazed during dynamic, complex passages like a top-quality push-pull. To be able to get this kind of astonishing performance—so close to Siegfried at only half the cost-- makes this amplifier a truly great value. The S-400 will redefine what you thought possible in a stereo amplifier.

Feature Summary


  • Fully logic-controlled automatic tube biasing: Re-biases between music passages, to keep tubes in optimal operating condition
  • Tube life: Front panel display shows hours of operation of the tubes—no more guesswork on when to change tubes
  • Switchable on-the-fly between tetrode and triode modes with built-in circuit protection
  • Logic-controlled soft-start sequence - extends tube life


  • Front panel fault display alerts user if any of the following conditions are sensed:
    • inadequate line voltage
    • power surge
    • any tube is operating out of its parameters
  • Automatic shutdown after fault is sensed


  • automated fuse testing
  • line voltage display
  • amplifier operating time (since new)
  • serial port for remote diagnostics


  • Precision regulated power supplies: For consistently musical performance and deep bass
  • Balanced input stage: For dynamic sound and superior noise rejection
  • Fully remote controllable and RS-232 Interface: For integration with centrally controlled systems
  • Phase switch


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Purchasing & Delivery

Free Delivery

Delivery is FREE on all orders over £50. In order to offer FREE delivery to UK customers, we use several premium couriers to ensure your delivery arrives safe. Most large orders (over 2kg) ship using DPD or DHL courier and smaller orders (under 2kg) by Royal Mail signed for services. The most appropriate courier will be chosen for the items ordered to ensure the quickest possible delivery.

Failed Deliveries

If you do not receive your order within 5 working days after receiving your shipping confirmation, please contact the courier with the tracking information provided to check if your order is being held. If you do not have tracking information, please contact for tracking details. If your order is kept by the courier, not collected and then returned to us, there is a charge for redelivery, so please ensure you contact the courier if you receive a missed delivery slip.

Warranty Information

Each product comes with a standard manufacturers warranty which can range from 6 month to 5 years. Many products are eligible for Kronos AV's 5 year warranty. Please get in touch to see if your order is eligible.

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