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MARCH 2013 • 97
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VTL’s 7.5 Series III – the
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Equipment Review
The VTL TL7.5 Series III
Line-stage (and MB450
Series III mono-blocs)
W
hen the VTL TL7.5 first appeared, way back in 2002,
it marked a serious watershed in the evolution of valve
electronics. For so long the poor and far from pretty
relation of sleeker, more stylish solid-state electronics,
the arrival of the 7.5 banished the oversized casework
and perforated bent metal chassis aesthetic. In fact, it was externally
indistinguishable from the solid-state competition. More importantly, it was
operationally indistinguishable too, with a practicality and versatility that
equaled the best; an elegant, twin-chassis package that oozed class.
Ten years on and the market for valve electronics has evolved – and so
too has the 7.5, reaching Series III status. The competition has split, some
playing catch up and trying to clean up their acts, others filing the contest
under “too hard” and reverting to the retro path. Where does that leave
the VTL? Still firmly atop the aesthetic and functional tree. The Series III
is externally identical to the Series I and functionally identical too, aside
from an internal switch that alters overall gain, testament to the clarity of
form and purpose embodied in the original design. What have changed are
important elements within the circuit itself, but to appreciate that evolution
it’s necessary to start with the original overall concept.
The TL7.5 should really be considered a hybrid design. It uses a two-box
chassis, separating the audio signal path from the noisy power supplies and
control/switching circuitry. The circuit in the VTL is fully complementary, with
a single 12AU7 per channel being used for voltage gain, direct coupled to
a FET-based buffer that supplies the necessary current. It’s an arrangement
that uses each technology for its strengths. Likewise, the substantial power
supply was built around solid-state MOSFET regulation in a series-pass
topology, avoiding the current limiting and lifespan issues that impact on the
performance of tube-regulated supplies. The audio circuit was a model of
simplicity, with very low global-feedback and using a single resistor ladder to
provide both volume and balance control.
So, what’s new? Let’s start with the power supply. Experiments
with a tube regulated supply yielded superior sonic results, but VTL
were reluctant to rely on valves in this critical application. Examining the
reasons for the superiority of the tube supply, they were able to develop
a new, shunt-regulated MOSFET design that delivered better dynamics
and signal performance than either the original MOSFET topology or the
tube power supply.
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By Roy Gregory
The tube gain-stage was re-engineered
for greater linearity, which allowed the
elimination complete of global feedback, while
the output buffer was also redesigned around
new J-FET-like devices sourced from
green technologies,
EQUIPMENT REVIEW / VTL TL7.5 SERIES III PREAMPLIFIER
offering a more valve-like behavior coupled
to greater extension, resolution and
linearity. Finally, the bypass capacitors used
throughout the circuit were completely
reassessed. Currently fashionable Teflons
were found to work well in the power supply,
delivering excellent detail and resolution, but
in the critical audio circuit, Polypropylene
was preferred for its natural, unexaggerated
balance. Roll these changes together and
sonically, the TL7.5, whilst still recognizably
the same animal, has taken a serious step
forward in sonic and, more importantly,
musical terms. I’ve been fortunate enough to
have a 7.5 Series III in residence for quite a
while, in conjunction with the MB450 Series III
mono-blocs reviewed back in issue 88. In that
time it has become the go-to pre-amp in a whole range of reviews, reflecting
both its sheer versatility and tractable nature: there’s nothing you can’t connect
to the 7.5, and nothing you can’t connect it to, given its full range of both singleended and balanced inputs and outputs, combined with its capability to really
drive long cables and handle wildly different input levels and system sensitivities.
Four inputs can be switched from single-ended to balanced configuration, with
two more and two tape loops operating in single-ended only. Input sensitivity
can be individually trimmed to accommodate different source components and
system phase can be reversed.
But what has made the VTL TL7.5 genuinely universal is its sheer
invisibility. Once it’s in the system, it simply gets on with the job. It’s not that it
doesn’t have a character, it’s more that you simply don’t notice it. This is the
Holy Grail of audio performance, and few components in my experience (and
even fewer line-stages) perform this trick quite as well as the 7.5. The few that
do are the keepers – the products that will stay in your system for a long, long
time – something that’s further underlined by the fact that VTL will upgrade any
7.5 to current status, a step that’s well-worthwhile.
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EQUIPMENT REVIEW / VTL TL7.5 SERIES III PREAMPLIFIER
What is it, in musical terms, which makes the TL7.5 such a significant advance
over its predecessor? I can best describe it as a more concentrated performer.
Whilst the character of any audio component can be broken down, discussed in
terms of traditional audio categories, like transparency, dynamics and separation;
and whilst all too often that dismantling of the audio performance mirrors similar
disconnections perpetrated upon the musical performance, in the case of the
TL7.5 the sound is so coherent and so holistic that it only really makes sense to
consider the way these aspects combine or alloy to create the overall impression.
Hence the term “concentrated”; by which I mean that there is a greater sense of
centered presence and energy, a greater sense of physicality to each instrument.
But it is not just about holding things closer, it’s also about holding them more
stable. So the thing about the VTL is the way it locates an instrument, almost
physically, within the soundstage and then keeps it there. What you don’t notice
is the sheer stability of the event. You don’t notice that instruments don’t move
with level or pitch. Whole sections of the orchestra don’t clamber forward into
an undignified central scrum every time there’s a crescendo, individual voices
or instruments don’t waver languidly within the mix. This absence of movement
passes unnoticed, simply because you only become aware when things do
move, when that movement destroys the spatial illusion, when instruments start
to migrate and draw attention back to the speakers.
The other thing that happens as natural result of this grounded,
concentrated presentation, is that there’s a greater differentiation of what is
instrument and what isn’t – which in turn creates a greater sense of energy, of
sheer musical power when the recording demands it. I’ve used the 450 Series
III mono-blocks with a considerable range of driving pre-amps, but combine
them with the TL7.5 Series III and the sudden surge of power is almost like you
turbo charged the amps. This sense of unfettered musical impact is founded
on the absolute integrity of the signal they’re being fed. This almost physical
sense of presence might not match the micro-dynamic textures available
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from the highest resolution devices, but
this is a different kind of resolve – one that
won’t brook any dilution or dismantling of the
musical message in search of mere detail.
But don’t get the idea that the TL7.5
Series III is just about BIG and LOUD. So
much of being truly invisible in the system is
about getting out of the way, about allowing
the expressive, fluid qualities in the playing
to shine through, the emotion in a vocal, the
way that two, or three, or four instruments
combine and play off of each other. Of course,
that doesn’t mean it can’t be loud too…
Play Elvis Costello’s ‘Little Triggers”
and there’s a centered impact to each drum
beat, a tactile shape and momentum to
the bass line, working together to underpin
and reinforce the beautifully modulated
and restrained vocal line. There’s a sheer
substance to the sound that matches
the power, purpose and attitude in the
performance that real brings that bitter mix
of sadness and anger alive. Likewise, the
open air recording, the massed voices that
open Peter Gabriel’s ‘Biko’ are spread wide
in a massive, open space. This is people
power plain and simple, the depth of the
emotion, the sense of collective grief (and
hope) heightened by the individual voices.
EQUIPMENT REVIEW / VTL TL7.5 SERIES III PREAMPLIFIER
It’s a powerful statement of musical intent
that is matched by the entry of the deep,
pulsing bass note, a beat that is tight and
solid, with edges, a pitch and a separate
space all of its own. As the music builds,
layer on layer, the 7.5 holds the two
acoustics, the two musical worlds separate
and distinct, never allowing that powerful
bass to spread, bleed or obscure the crowd
of voices. It might seem a small thing but its
adds real power and impact, a whole new
dimension of distance, of contrast between
those inside and those outside the events.
Gabriel could have mixed the song as a
straight studio track, but it works so much
better this way. The beauty of the 7.5 is that
it tells you that – and why that is.
Technical Specifications
Type: Tube-based fully complementary
By allowing each voice or instrument in a recording its own space, its
own existence, but by also preserving the relationship between the pieces and
players, the TL7.5 brings the core of the music right to the surface, imbuing
performances with a feeling of purpose and intent that heightens their power
to move and immerse the listener.
This ability to both separate and yet bind the music’s elements together
is an awfully neat trick if you can pull it off, and in this musically vital respect
the combination of 7.5 and MB450 is blessed indeed. In no small part that
is down to the ability of the line-stage to meet the demands of any input,
the power-amp to not just drive any speaker, but also adjust its damping
factor to optimise the coupling. But as good as the 450 is – and it’s a mightily
impressive beast – there’s no escaping the fact that it takes a whole step up
in terms of power, impact and sheer musical authority when driven by the 7.5
Series III. With power available to handle any musical programme, the grip to
hold things steady and the confidence to let them breathe, these Series III VTL
products aren’t just better than their predecessors, they represent a step up
in audio terms but a step change in musical communication, especially when
used together. If you want the music AND the message, and you want it right
there right now, then the TL7.5 Series III is a great place to start, the MB450
Series IIIs the perfect partners. Costly to purchase and demanding to house
they may be, but these electronics will deliver the warm, beating heart of a truly
great system; for once, value really isn’t an issue. +
line-stage
Tube Complement: 2x 12AU7
Inputs: 4 pairs balanced/XLR or RCA
single-ended. 4 pairs single-ended/RCA
Input Impedance:50kOhms (20kOhms
min)
Outputs: 2 pairs balanced XLR, 2 pairs
single-ended RCA, 2 pairs single-ended
RCA buffered Tape Out
Gain: <20dB
Output Impedance: 25 Ohms (150
Ohms max)
Dimensions (WxDxH): Control Chassis –
445 x 445 x 102 mm, Audio Chassis – 445
x 445 x 153 mm
Weight: 34kg (packed)
Price: £19,995
Manufacturer: VTL
URL: www.vtl.com
UK Distributor: Kog Audio
URL: www.kogaudio.com
Tel: +44 (0)24 7722 0650
(For full details of the MB450 Series III,
please see Issue 88)
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ISSUE 97
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