Rooster Review - Sound On Sound
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Thermionic
Culture Rooster
Valve Microphone Preamp & EQ
Paul White
Is this latest addition to the Thermionic Culture flock
something for the company to crow about?
o appreciate anything built by UK
company Thermionic Culture, you
need to know something about the
philosophy of their founder, Vic Keary,
a larger-than-life character who relishes
building larger-than-life tube-based audio
gear. Vic set up the all-tube Chiswick Reach
studio in West London and then moved into
small-scale manufacturing with engineer
and co-founder Jon Bailes, who oversees
the mechanical engineering and visual
aspects of the products — all of which
seem to have curiously bird-related names
— before being joined by studio engineer
Nick Terry. They have a philosophy of not
using any solid-state circuitry in the signal
path, although, of course, they may use
it elsewhere, such as in power supplies.
The team confess to being obsessed with
tube-based audio equipment and they
all seem to dislike the sound of modern
solid-state circuitry. I’m not sure anyone has
dared to ask them what they think about
digital audio!
Although many Thermionic Culture
circuit designs hark back to the pre-vintage
days of the mid 20th century, they’ve done
whatever they can to reduce noise and
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distortion to meet the needs of today’s user,
through the use of high-quality resistors
and capacitors where appropriate, selected
tubes and carefully laid-out PCBs and
hand wiring.
Ruling The Roost
The Rooster, which I’m reviewing here, is
a hefty 2U, twin-channel, tube-based ‘mic/
line plus DI’ preamp with EQ. It also borrows
heavily from the distortion section of the
company’s Vulture.
The mic/line XLR connections are
on the rear panel, while the unbalanced
instrument DI is on the front. Each channel has its own
phase (polarity-invert) switch and 48V phantom-power
switch. The control panel is an unfussy black, with clear
legending, chunky knobs and traditional toggle or rotary
switches. Even the power light is analogue, although there
is a small concession to modernity in the form of simple
red-green-yellow LED output-level metering. The rear panel
is also very straightforward, with XLRs for the mic and line
inputs, XLRs for the two channel outputs and an IEC mains
inlet with adjacent voltage selector. Unlike most professional
studio equipment, the output was unbalanced on the review
model. Since I completed the review, a balancing-transformer
version has been released too, and it may even be possible
to retrofit the new option (you’d need to speak to distributors
Unity Audio about this). Given that cable runs from the
unit are likely to be short, the lack of balancing shouldn’t
present a problem, though, providing you take care to avoid
ground loops. Inside, a torroidal transformer in its own
screened area powers the circuitry, and all the tubes are fitted
with screening cans.
The input stage employs a custom 1.2kΩ-input Sowter
audio transformer, feeding an ECC81/12AT7 tube — so this
part of the circuit is based on a fairly traditional tube preamp
topography. The EQ section that follows is designed for
sweetening or fine-tuning rather than surgical reconstruction,
with a broad bass-lift control peaking at 60Hz, a switchable
mid/high-lift (operating at 2.5kHz band-pass, 4kHz band-pass
or 7kHz shelving) and a separate mid-cut, centred at 700Hz.
There’s also a six-position rotary bass-cut switch, which is
derived from the circuitry used in the company’s Earlybird
2 preamp, and a switchable low-pass filter to trim off the
excessive highs.
So far it all seems very polite… but no Thermionic Culture
product would be complete without a dose of quirkiness,
and you’ll find plenty of that in the ‘Attitude’ section. The
Attitude circuit uses a 5725 tube to create distortion effects,
which range from subtle and musical to very obvious and
confrontational. This is accomplished by switching the
tube between triode and pentode modes via a front-panel
toggle switch, and then setting one of six negative feedback
amounts via the rotary Attitude switch. In the triode position,
the tube, which runs from a reassuringly high-voltage HT
rail, provides controllable distortion depending on the
amount of feedback applied. This arrangement results in
the amount of distortion being very low when the Attitude
switch is set to minimum. When pentode mode is selected,
the third-harmonic distortion becomes more dominant, and
with the Attitude control set to one of its higher positions
Thermionic Culture Rooster £1749
pros
UÊWarm, punchy retro sound quality.
UÊGreat analogue EQ.
UÊVariable distortion characteristics.
UÊNot cheap, but certainly realistically priced.
UÊBalanced and unbalanced output versions available.
cons
UÊNone.
summary
A seriously esoteric all-tube preamp/equaliser at an affordable price.
EFDFNCFS … www.soundonsound.com
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THERMIONIC CULTURE ROOSTER
the distortion becomes much more
obvious. At the maximum setting there’s
no negative feedback at all, so the amount
of distortion is quite high — especially if
the input level is also turned well up. After
all this mayhem, the signal passes through
an ECF80 output stage, which acts as
a low-impedance output buffer.
Although a great deal of thought has
clearly gone into the design, the only way
to evaluate a preamp such as this, where
distortion is used as an effect, is to do so
subjectively. On paper, most tube-based
audio gear tends to look worse than its
solid-state counterparts, because tubes are
inherently more noisy and produce more
distortion. However, as long as the noise
floor is low enough that it doesn’t stand in
the way of making good recordings — and
the distortion is musically satisfying — the
results can be sheer magic.
Rooster With Attitude
As a mic preamp, the Rooster has that
punchy character that’s associated with
certain transformer-input mic amps, and
this comes across even when the Attitude
switch is at its lowest setting in triode
mode. There’s no apparent distortion when
the Rooster is used in this way but the
sound still has a character that’s missing
from a typical solid-state mixer mic-amp.
As you increase the Attitude setting, the
negative feedback is reduced, so that the
gain increases — which means you need
to back off the output level control to keep
the output signal steady. At the highest
Attitude setting, some distortion may be
noticeable if the input gain is also set fairly
high, but in the main it comes across as
a thickening of the sound that works well
on certain voices and also adds a nice sense
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of stability to DI’d bass guitar parts.
Switching to pentode mode ups the
ante on the distortion front, although the
low-numbered settings can still sound
nicely smooth and musical. At higher
settings and with a lot of input gain, the
distortion becomes rather more obvious, to
the point that it can sound quite crunchy.
In the main, I’d avoid going this far, as
large amounts of distortion without the
low-pass filtering of a typical guitar speaker
cabinet can sound unpleasantly harsh, but
at least the option’s there if you’re working
on death-metal vocals! Fortunately, the six
switch settings plus the input gain setting
give you plenty of control over how much
tube coloration is added, and for treating
drawbar organs or tine pianos (such as
the Rhodes) the pentode mode may be
exactly what’s needed to capture that retro
overdriven sound. For more subtle warming,
the triode mode produces more of a genteel
tape-saturation type of effect.
I have to say that I really like the sound
of the EQ section of this preamp. Forget
10-band parametrics — these few simple
controls are perfect for sweetening vocals
and most instruments, and make it easy
to produce a sound that punches through
a mix without being thin or harsh. As with
most well-designed analogue equalisers,
you may only need to make quite small
adjustments to achieve the desired result
— and even when you need more extreme
settings, the sound still stays musical and
well focused.
Tried & Tested
At the time of writing, there was no on-line
manual or even spec sheet for the Rooster,
but that doesn’t really matter, because it’s
how it performs in a real-life situation that’s
important. Providing the input stage was
run at a sensible level, I could detect no
noise issues in typical studio close-miking
applications, and the tonality has a lovely,
vintage directness to it that helps sounds
sit well in a mix without your having to
resort to unseemly brightness to make them
heard. For a ‘clean-with-character’ tonality,
the triode mode excels, whereas the slightly
more ebullient pentode mode works well on
instruments that traditionally rely on a bit of
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distortion to complete their sound — some
styles of bass guitar, electric piano, organ
and electric guitar, for example.
The EQ section did exactly what I wanted
without strangling the sound, as some
less sophisticated equalisers and plug-ins
tend to do, so I’ve no complaints at all in
this department — and even the limited
number of frequency options didn’t seem
to get in the way of great results. Adding in
some low end, I was rewarded with depth
and punch without everything turning into
a woolly mess. The mid controls felt wide
and sweet and, with the 7kHz setting, the
high/mid control brought out the clarity and
transparency of a sound without making
it brittle or harsh. What this boils down to
is that you can add a lot of this EQ if you
need to, without compromising the integrity
of the sound, even though in most cases
you probably won’t need very much to
get the job done.
Cock-a-doodle Do?
A processor such as this one may seem
costly, but when you consider that you
get a pair of seriously characterful mic
preamps as well as an effective retro-style
analogue equaliser in an all-tube format,
the cost isn’t really over the top. In fact,
many US-made boutique tube processors
will cost rather more without offering the
same vintage vibe.
While the designers would clearly love
to live in an all-analogue world, a preamp
like the Rooster could bring some welcome
analogue character to a digital studio, and
if you’re in the market for something a bit
more exotic to use as a front end, this could
be exactly what you’re looking for.
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£
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Review model (unbalanced outputs) £1749;
Transformer-balanced output version £1995.
Prices include VAT.
www.thermionicculture.com
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This article was originally published in
Sound On Sound magazine, December 2008 edition.
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