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Siegfried Series II Reference Mono Power Amplifiers

  • Flagship VTL Amplification
  • Please Get in Touch for Pricing
  • Phenomenal Performance, Power & Control
  • Auto-Bias Set Up, Fault Sensing
  • 650 Watts per Channel


The Siegfried is the VTL flagship amplifier, the absolute pinnacle in tube design and technology. The original Siegfried launched in 2003 and was the first valve amplifier in the world to feature Auto-Bias and Fault Sensing.
The Siegfried has a magnificent reputation and a performance second to none. It’s one of those products that you often see in photographs online showing true reference high end systems. A number of world-class loudspeaker manufacturers use a pair of Siegfrieds as their reference point for voicing their designs.
The reviews that the Siegfried has received the world over speak for themselves as well, to quote Michael Fremer from Stereophile magazine – “Remarkably quiet, wideband, as linear and tonally neutral as the best solid-state amps, and with just a kiss of the effortlessness tube lovers find so addicting, the VTL Siegfried II was as neutral and as uncolored as any tube amp I’ve listened to.”
If you want to get to the heart and soul of the music the Siegfrieds are the amplifiers to do it. Regardless of what genre of music you favour the Siegfried delivers so much clarity, transparency and raw emotion. With 650 watts per channel in Tetrode mode (330 in Triode) they offer effortless control over whatever speaker you choose to partner them with, each mono block packs in a dozen of the superb 6550 valves. KT88 valves are available as well as a cost option. Sonically they are a smooth and sweeter than the 6550 which offer more dynamics and punch.
The fault sensing on the Siegfrieds is superb, the LED display will inform you if a valve has blown, but it won’t stop playing music. You can monitor tube hours, internal temperatures, mains voltage. It can even be connected to a computer to generate a report for all the faults/issues it has ever sensed.
Perfect embodiment of modern and ancient technology being used together harmoniously!
Quite possibly the best mono power amplifiers in existence!

The new Series II version of the renowned Siegfried platform features a complete re-working of the entire signal path. Upgrades include a fully balanced differential input stage driving a differential phase splitter and a lower impedance push-pull output stage with a dramatically improved, fully balanced and enhanced interleaved and coupled output transformer.

The new Siegfried Reference monoblocks gain further sonic benefits with a shorter, faster and fully balanced negative feedback loop, with zero global negative feedback. The negative feedback loop completely eliminates ringing and requires no capacitor compensation to maintain critical phase integrity and information. The result is an amplifier that remains stable even under the most demanding loads.

Adjustable precision-regulated plate, screen and bias supplies hold the output tube operating point constant even under AC and main power supply fluctuations, and stabilizes the critical power supplies yielding tonal stability and sonic integrity especially during complex, dynamic signal conditions.

Another new feature is a user adjustable Damping Factor feedback control that allows the user to adjust the amplifier’s output impedance by varying the amount of negative feedback. Impedance can now be precisely set to suit the listener’s taste, and to improve control of the loudspeaker loads to deliver best performance.

The 4 settings are:

  1. Low – Lowest damping factor, good loudspeaker control, most natural sound.
  2. Medium – Better loudspeaker control, with some impact on sound quality
  3. High – Best loudspeaker control, with a little more impact on sound quality, but on speakers that need the control the sonic improvement is clear
  4. Max – Maximum damping factor, but sonic impact is noticeable

As previously mentioned Low and Medium are the most popular settings, although it will vary from user to user depending on the speakers being used.

Finally, the amplifier has been substantially re-voiced with premium Mundorf silver oil capacitors, for a sweeter, more extended top end and mid range tonality that sounds more relaxed, with better flow and integration. Input stage capacitors are also bypassed.

  • Fully balanced differential circuit – single-ended signal produces balanced signal at output
  • Re-designed fully balanced differential input and driver stages for increased signal swing, bandwidth and stability
  • Zero global Negative Feedback
  • Shorter, faster feedback loop for greater tonal control without phase shift.
  • Improved handling of loudspeaker loads for greater signal stability.
  • The amplifier is unconditionally stable, without the need for any capacitor compensation.
  • New current source for lower sonic impact in single-ended mode
  • Lower impedance output stage for improved loudspeaker control
  • Dramatically increased interleaving and coupling in the balanced VTL proprietary Reference output transformer, for wider bandwidth and zero ringing
  • Variable user-adjustable DF feedback control to vary output impedance and damping factor for optimal matching to speaker load
  • Software microprocessor controlled
    • Tetrode/Triode Switchable
    • Auto Bias, Fault Sensing
    • Current in-rush limiting
    • Standby Mute function; with reduced tube current for increased tube life
    • Fully bi-directional RS-232 control
  • 650 watts per channel in tetrode; 330 watts per channel in triode
  • Uses twelve 6550 or KT-88 tubes per monoblock
  • Adjustable precision-regulated plate and screen supplies for stable operating point; discrete regulated input and driver supply for greater signal resolution and tonality
  • Adjustable precision-regulated bias supply for greater signal resolution and noise rejection and improved isolation from mains supply variations; output operating point does not change with AC power fluctuations
  • Improved Autobias and fault sensing system to operate in fully balanced differential mode; amplifier is fully protected against output tube failure; no need for precision matching of output tubes
  • All premium Mundorf silver oil caps in signal path
  • Film bypass of power supply caps for greater HF resolution
  • Extruded aluminum front panel with luxurious, modern look – black and silver options available
  • Precision regulated B+ and screen supplies
  • Rigid construction and improved ventilation for lower operating temperature
  • Factory upgradeable from Series I

More Reading

VTL Siegfried Series II Reviews Page

Additional information

Power Output

Tetrode: 650W, Triode: 330W

Valves Used

12 x 6550 or KT-88, 1 x 12AT7, 2 x 12BH7


90 Kg (per Monoblock)


W x D x H 292 x 610 x 610 mm

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