VTL MB-450 Series II Signature monoblock power amplifier

[Κώστας Φ.]

Description: Tubed monoblock power amplifier.
Tube complement: one 12AT7, one 12AT7, eight 6550C.
Inputs: 1 pair unbalanced (RCA), 1 pair balanced (XLR).
Outputs: 1 pair binding posts.
Rated power output at <2.5% distortion: 425W into 5 ohms, Tetrode mode; 225Wpc into 5 ohms, Triode mode.
Frequency range: 20Hz–20kHz.
Output impedance: 5 ohms.
Input impedance: 42k ohms.
Input sensitivity: 2.0V for full output.
Power consumption: 30W at idle, 1000W at full power.
Price: $13,500/pair.



"In the VTL MB-450 Series II Signature, the rack-mount handles and dark industrial look of the original MB300 and MB-450 (footnote 1) are replaced by a thick, elegantly handsome, curvaceous faceplate of brushed aluminum that frames a dark glass panel, through which glow the input and driver tubes. Three small buttons and accompanying LEDs select Mode, Power, and Mute. And that's it for the front panel.

On the rear panel are the main On/Off switch, a set of speaker binding posts, RCA and XLR inputs, a switch to select balanced or single-ended operation (I used the single-ended), a 20-amp IEC jack, five fuse holders, and a trigger connector for remote power-up via another source, such as a preamplifier. Much like the original VTL 300, from which the MB-300 and MB-450 are derived, the tube complement comprises eight 6550C output tubes, and one each 12AT7 and 12BH7 tube for the input and driver stages.

The MB-450 Series II incorporates many of the technological advances found in VTL's flagship monoblock, the 800W Siegfried Reference. These include "smart tube," logic-controlled auto-biasing circuitry, which continually checks and optimizes each tube's performance while providing a series of fault-sensing diagnostics for each tube via a series of LEDs. VTL maintains that the auto-bias circuit doesn't affect the sound quality because it's not part of the signal path, and monitors and biases the tubes only when music isn't being played.

The basic audio circuit, not so far removed from the original MB300, features a fully balanced input stage with separate input and driver power supplies, a "long-tailed pair" differential phase-splitter, and, of course, a push-pull output stage. Also included are a new, precision-regulated power supply and upgraded internal parts.

According to VTL, the screen power supply's "high-tension" voltage-regulation system, consisting of a 30-amp MOSFET connected between two massive banks of capacitors, working in conjunction with the main supply, to maintain proper voltages within <1% deviation at full output. That, VTL claims, helps give the amp a "fast, dynamic" sound.

With their auto-bias system's comprehensive tube-monitoring abilities, VTL strives for ultra-reliability in conditions of high current draw: the circuit immediately shuts down the amp in case of a potentially "fatal" tube fault. A separate fuse for each high-tension supply and automatic monitoring of fuse conditions add more levels of protection. Of course, protection doesn't mean complete reliability—tubes fail, and have been known to take out amplifiers when they do—but such redundancy of protection is comforting.

...

The VTL MB-450 Series II Signature monoblock power amplifier is easy to listen to. It's even easier to recommend." -- Michael Fremer



"In common with the other VTL amplifiers reviewed by Stereophile, the MB-450 Series II Signature offers generally excellent measured performance, compromised only by the design decision (on sound-quality grounds) to use a low level of loop negative feedback. It is indeed a powerhouse. And I continue to be impressed by the wide bandwidth of VTL's Signature output transformer." -- John Atkinson



Full Review: Stereophile.com

 

[Μιχαλης Σπερτος]

Οι οπαδοι των SΕΤ με αρχαιοπρεπεις DHT μπορουν να κανουν ενα διαλλειμα για να δουν τι σημαινει Συγχρονος Ενισχυτης λυχνιων με Συγχρονη σχεδιαση, και μετα "τα κεφαλια παλι μεσα"

Και να σκεφτει κανεις οτι η συγκεκριμενη σχεδιαση δεν ειναι τιποτε περισσοτερο απο μια απλουστευση της παρακατω :bravo:

http://www.wolcottaudio.com./WA_presence.htm

(εαν ενδιαφερεται κανεις μπορω να του στειλω τα papers του Wolcott)


Ομως ο VTL signature εχει μερικα δυνατα στοιχεια στην υλοποιηση.
Το σπουδαιοτερο ισως ειναι αυτο. Πως να κανεις ενα κλασσικο μετ/στη εξοδου να πλησιασει (χωρις να φτασει ακριβως) τις ιδιοτητες ενος Toroidal.


The VTL Signature Ultra-Wide Bandwidth, Low-Loss Output Transformer
VTL continues a tradition of emphasis on simple elegance and design innovation with our high fidelity, ultra wide bandwidth Signature output transformer.

• Multiple tight layering and coupling for extended frequency response
• Custom winding for clean square wave response, precise impedance matching to output tubes
• High efficiency with low insertion loss for optimal current transfer, set for 5 ohm ideal speaker load, utilizing whole secondary

The Soul
Behind the sleek new cosmetics of the VTL Signature MonoblockAmplifiers, a revolutionary new component is added to further improve the resolution of the amplifier. The Signature Transformer, an ultra-wide bandwidth, low loss output transformer, now comes standard with all VTL Signature Monoblock amplifiers. The Signature transformer's major strength is that it can deliver the current in the bass, while at the same time maintaining the speed in the high frequencies, dramatically improving the square wave response of the amplifier, and translating to a far cleaner sound.
The Innovation
Traditional output transformers cannot match the performance of the VTL Signature transformer. The biggest challenge with designing a big output transformer is that it needs to be as big as possible to be able to handle the bass current, but it gets harder and harder to keep the speed in the top end as the size of the transformer increases. If the coupling is not watched carefully, the capacitance and leakage inductance will roll off the high frequencies.
Technically, the design highlights of the Signature output transformer are a substantial increase in the number of interleaved sections over VTL's previous output transformers, dramatically improving the coupling between the primary and secondary windings (and even the individual wires) and increasing the efficiency (by lowering the insertion loss) of the transformer. The multiple sections and better winding to winding coupling of the Signature transformer gives the amplifier the capability to pass full power right out to the frequency extremes, which is the major reason for the wider frequency response and improved resolution, particularly in the top end.
An additional feature of the Signature output transformer is that the primary impedance of the transformer is more precisely matched to the plate impedance of the output tubes, and with the impedance set for optimum speaker load of 5 ohms gives the most efficient current transfer from the output tubes to the speaker load. This allows the VTL amplifiers to better handle the fluctuations in loudspeaker impedance and gives much more flexibility to handle a wider range of loudspeaker loads.

 

[Σπύρος Μπλάτσιος]

Απάντηση: VTL MB-450 Series II Signature monoblock power amplifier

[hi end mode]Αφού δεν το φέρνει ο Musiclover δεν λέει το μηχάνημα ρε. Άσχετοι...[/hi end mode]


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