VTL Stereo Power Amplifiers

VTL manufacture 4 stereo power amplifiers with big variances in both performance and cost.

ST85 Stereo Power Amplifier

The ST85 is the entry level stereo power amp from VTL and is priced at £3450.00. The natural partner to go with the ST2.5i preamp the ST85 delivers a meaty 60 watts channel and gives you a full taste of the VTL sound. Utilising 4 EL34 tubes, which is a classic workhorse tube design and works exceptionally well with a short signal path which makes it ideal for use in a VTL, what with their simple circuit ethos.

The ST85 works best with a standmount or smaller floorstanding speaker and sounds smooth and sweet, but don’t mistake that as being dull and laid back. It is dynamic and incredibly well balanced. With the right speaker this is a devastingly capable power amp.

With RCA inputs, a pair of conventional binding posts (that accept both spades and 4mm plugs), and a switch to alternate between tetrode and triode, the rear panel is nice and simple.

  • Compact Stereo Amplifier ideal for entry level systems
  • Musical sounding EL34 tubes in the output stage
  • Tetrode/Triode Switchable
    • 60 Watts per channel in tetrode
    • 30 Watts per channel in triode
  • Extruded aluminum front panel with luxurious, modern look – black and silver options available
  • Front panel comes with a window of thick tinted glass where you can see the glow of tubes

ST150 Stereo Power Amplifier

The ST150 is the most popular stereo power amplifier in the range and for good reason, with 150 watts per channel (in tetrode mode) this power amp has the ability to drive and control a much wider range of larger and more demanding speakers compared to the ST85.

Using 6550 tubes, it sounds sweet, fast, articulate and dynamic. When pushed it never hardens up or becomes aggressive in nature it just keeps on delivering that traditional sweet, seductive VTL sound.

I’ve a couple of customers with big systems with an ST150 at the heart of them doing sterling service, it really is a tremendously musical amplifier. In tetrode mode it can play loud and it seems to relish the challenge. In triode mode it becomes less efficient as power drops to around 70 watts, but if you have a small, sensitive pair of speakers and you favour jazz and simple vocals it delivers a sweetness which is hard to beat.

The rear panel is the same as the ST85 with RCA inputs, a pair of conventional binding posts (that accept both spades and 4mm plugs), and a switch to alternate between tetrode and triode.

The ST150 is priced at £6900 with 6550 valves (KT88 are an option at the point of purchase for an additional £200)

  • High energy storage power supply >200 joules
  • VTL proprietary output transformer
  • Very low-noise floor with specially designed grounding scheme
  • Tetrode/Triode Switchable
  • 150 watts per channel in tetrode
  • 70 watts per channel in triode
  • 4 6550 tubes per channel with individual bias setting for each tube
  • Audiophile grade film and foil caps used in the signal path
  • Extruded aluminum front panel with luxurious, modern look — black and silver options available
More Reading - Ken Kessler - Hi Fi News Magazine (ST150 Review) 

S-200 Signature Stereo Power Amplifier

The new S-200 is the entry level power amplifier in VTL’s Signature range of products, although don’t let the term ‘entry level’ fool you, this is anything but entry level.

The S-200 has all of the typical VTL sonic attributes but it also has huge amounts of raw power and control, giving vice like grip on just about any speaker available.

VTL wanted to deliver the performance and features of the MB-185 and MB-450 mono-blocks but in a single space saving chassis and with the S-200 they have suceeded!

The 200 watts per channel amplifier is packed with technology VTL has spent years developing (Bear with me, we’re about to go techie again!). A fully balanced differential input stage drives a differential phase splitter and a lower impedance push-pull output stage with a custom made, fully balanced, interleaved and coupled output transformer. Like its Signature stable mates, the amplifier incorporates VTL’s SmartTube technology with automatic bias adjustment and fault sensing, making this amplifier especially welcome to music lovers who value ease of use. With the S-200, there’s no need to guess when or if a tube may need to be replaced.

To keep the output tube operating point constant and stabilize the critical power supplies, even under AC and main power supply fluctuations, the S-200 deploys adjustable precision-regulated bias and screen supplies, yielding tonal stability and sonic integrity especially during complex, dynamic signal conditions.

The S-200 also features 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 3 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

The S-200 bears a similar sonic signature to its bigger brothers, the MB-450 Series III Signature monoblocks. The mid bass authority and control is excellent while the midrange and top end reflect natural timbres and instrument colours effortlessly. The amplifier’s agility and speed, its very low noise floor, and its ability to drive a wide range of speakers are distinct features that few other tube amplifiers in this price category can offer. Pair it with VTL’s TL5.5 Series II preamplifier for one of the most compelling and seductive sounds available anywhere close to the price, put it with a 6.5 and the performance steps up considerably.

The S-200 Signature Stereo Power Amplifier is priced at £12500 with 6500 tubes, with KT88 tubes fitted it costs an additional £200 at the point of purchase.

Features

  • Fully balanced differential circuit – even single-ended signal produces balanced signal at output
  • 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
  • Superior handling of loudspeaker loads for greater signal stability
  • The amplifier is unconditionally stable, without the need for capacitor compensation
  • Tube-like JFET type current source maintains sonic integrity in single-ended mode
  • Lower impedance output stage for improved loudspeaker control
  • Proprietary designed interleaving and coupling in the balanced VTL Signature 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
  • 200 watts per channel in tetrode; 100 watts per channel in triode
  • Uses eight 6550 or KT-88 tubes
  • Adjustable regulated screen supply 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
  • 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
  • Film bypass of power supply caps for greater HF resolution
  • Extruded aluminum front panel with luxurious, modern look – black and silver options available
  • Rack mountable
  • Rigid construction and improved ventilation for lower operating temperature
More Reading - Hi-Fi News Magazine (S-200 Signature Stereo Power Amplifier)
S-400 Series II Reference Series Stereo Power Amplifier
The S-400 is the flagship VTL stereo power amplifier and sits directly below the mighty Siegfried. With 300 watts per channel in Tetrode mode (150 in Triode) the S-400 is a seriously powerful and capable amplifier.
For the latest Series II revision VTL has re-worked 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. Equipped with the same “SmartTube” technology as the Siegfried II, the S-400 deploys Auto Bias and Fault Sensing, precision-regulated power supply technology, and bi-directional RS-232 control, giving unparalleled flexibility and ease of use.

The S-400 Series II gains 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.

As with the S-200 above another great 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 3 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

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.

The immediate thing you hear when you listen to the S-400 is the noise floor, or the lack of one. You get an inky black background which really lets you hear everything that is going on in the music.

You get a huge soundstage which is tall, wide and deep which paints a superb picture of what is going on in the mix. The high power of the S-400 delivers real dynamics and most importantly control and the whole presentation is just effortlessly musical.

Listening to music through the S-400 II amplifier is an exciting and invigorating experience!

Priced at 35175.00

Features

  • Fully balanced differential circuit – single-ended input 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 greater sonic integrity 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
  • 300 watts per channel in tetrode; 150 watts per channel in triode
  • Uses twelve 6550 or KT-88 tubes
  • 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

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