Warm Audio TB12 Tone Beast
on test
Warm Audio
TB12 Tone Beast
Mic, Line & Instrument Preamplifier
Hannes Bieger
O
riginally conceived as a preamp
card for the input channels of the
company’s consoles, the classic
discrete design of API’s 312 mic preamp
has played an integral part forming the
sound of rock music, and American rock in
particular. API still build preamps based on
the original early-’70s design, and several
Warm Audio
TB12 Tone Beast £549
pros
• Ample tone-shaping capabilities.
• Fully discrete circuit design.
• Cinemag transformers.
• 71dB gain.
cons
• External PSU.
• Brightness of the LED level meter.
summary
The Warm Audio TB12 Tone Beast, based
on the classic API 312 preamp circuit
topology, offers plenty of tone-shaping
options at a very affordable price. Some of
its basic ingredients, such as the high-quality
Cinemag transformers and the fully discrete
Class-A signal path, can usually only be
found in more expensive units, and few
corners seem to have been cut designing
this preamp. Anyone in the market for
a good-sounding and versatile yet affordable
preamp should have a look at the Tone
Beast, but it will appeal most of all to those
planning to explore its saturation and
distortion capabilities.
180
Warm Audio’s latest preamp offers surprisingly
high quality in an affordable package.
other manufacturers now offer their own
takes on this piece of recording history,
for a number of reasons. First, the 312
offers a great sound, which is meaty and
powerful, with a pronounced mid-range.
It’s also a very simple design, comprising
little more than a pair of input and output
transformers and a single discrete,
Class-A op-amp. This means not only
that a preamp based on the 312 layout
is fairly easy to manufacture (though one
needs high-quality ingredients!), but one
could also argue that the original design
is almost begging for modifications and
enhancements. This is exactly what Warm
Audio, based in Round Rock, Texas, have
done: they’ve taken the basic layout of
the 312, as used in their existing WA12
preamp, and built their own versatile
concept around it, essentially doubling
all the important circuit elements for
maximum sonic variety. The result is
a single-channel 1U rackmount device they
call the Tone Beast.
Overview
The format means that, unlike with the
original ‘bare bones’ 312, there’s ample
space on the faceplate for controls.
Indeed, the Tone Beast comes with all
the bells and whistles one can expect
from a modern well laid-out mic preamp,
including dedicated switchable mic, line
November 2013 / w w w . s o u n d o n s o u n d . c o m
and instrument inputs as well as phantom
power, a -20dB input pad, a polarity switch
and an 80Hz high-pass filter. All switches
are accompanied by red status LEDs,
a simple but useful feature that should not
be overlooked. This input control section
already makes the Tone Beast more flexible
than some of its obvious competitors, but
the TB12 offers much more...
Both its Gain & Saturation and Tone
Control sections can transform the preamp
into a saturation generator, with a sonic
scope ranging from extremely subtle
coloration to the wildest fuzz sounds. The
stepped gain pot sets the amplification
in a range between +29 and +65 dB. It is
paired with an output pot ranging from full
attenuation (minus infinity) to unity gain.
This, in turn, allows the amplifier stages
to be driven hard without overloading the
next unit in the signal path, which opens
up a vast range of tonal options.
In order to explain precisely what the
Tone Control section has to offer, we have
to peek under the lid and consider what’s
inside the unit. Interestingly, the Tone
Beast doubles most parts of its signal
path, to offer sonic alternatives through
the deployment of different components.
Warm Audio have equipped the TB12
with no fewer than three high-quality
American-made Cinemag transformers,
one of which is a custom design, tailored
to Warm Audio’s specification. There’s
a single input transformer, but two output
transformers can be swapped at the
flick of a switch. The first, a steel-core
transformer, boasts a rich mid-range
and a tone which can be considered
more ‘vintage’-sounding, whereas the
50-percent-nickel-core transformer yields
a more linear, transparent response. Both
transformers can also be bypassed, which
results in an 8dB level drop but an even
cleaner signal.
Following the same logic, the other
key ingredients of the signal path, the
op-amps, can be swapped as well. The
Tone Beast is built around two discrete
op-amps, but, following the original 312
design, only one is active at any given
moment. One, the x731, is based on
the Melcor 1731, a predecessor to API’s
famous 2520 op-amp, and this is the more
coloured option. The other, called x18, was
modelled after Dean Jensen’s classic 918,
which is a cleaner and more open-sounding
op-amp. Both are socketed, following API’s
classic six-pin layout, and in the operation
manual, Warm Audio actively encourage
users to experiment with the many
compatible third-party op-amp blocks for
yet more subtle sonic variety.
The capacitors in the circuitry
surrounding the op-amps can be
swapped, too. The ‘vintage’ setting
employs tantalum capacitors, while the
‘clean’ option relies on electrolytics.
This is by far the most subtle of all the
modifications, and in some situations
it doesn’t change the sound much at
all, but its effect becomes increasingly
apparent as the preamp is driven further
into distortion. The palette of controls is
rounded off by the Tone switch, which is
active on all inputs (microphone, line, and
high impedance). On the mic input, with
the Tone switch disengaged, the input
impedance is 600Ω. Activating the Tone
switch sets the impedance to 150Ω, giving
an additional 6dB level boost (increasing
the maximum gain to +71dB), which may
be more suitable when recording with
a passive ribbon mic.
Finally, and slightly unusually, the
high-impedance instrument signal is
fed into the input tranformer via a little
additonal discrete transistor circuit.
This way, instrument signals can also
benefit from the sonic character of the
input transformer.
As well as the anticipated inputs and outputs, the
Tone Beast also offers insert slots for integrating
other processors in its signal path.
Although that’s it for the on-board tonal
tweakery, it’s still not all the Tone Beast
has to offer, as there’s an insert point into
which external equipment such as EQs and
compressors may be patched. This comes
between the op-amps and the output
transformers.
Value For Money
The Tone Beast feels sturdy, uses quality
components and should provide years
of reliable performance. In fact, I find it
amazing that Warm Audio can offer a fully
discrete Class-A circuit with components
of this quality, complete with the various
alternative options, in this price bracket.
Usually, this kind of technology can only be
found in units costing two or three times as
much as the TB12.
Inevitably, though, a few corners have
been cut in order to make this possible,
and while some take nothing away from
the overall qualities of the unit — and
while I did not find any real flaws — there
are some points I’d like to discuss. First,
the Tone Beast relies on an external
w w w . s o u n d o n s o u n d . c o m / November 2013
181
on test
Warm Audio TB12 Tone Beast
Quality components: the circuit employs three
Cinemag transformers and two discrete op-amps
(classic API 2500 six-pin layout).
‘wall-wart’ type power supply. This is not
a problem per se, and a quality internal
PSU would have driven the manufacturing
cost up quite a bit, but most high-end
units employ internal power supplies
unless there’s good reason not to, and
some manufacturers even take pride in
over-designing them! Secondly, I’m not
a big fan of the five-segment LED level
meter: it employs blue, green, yellow and
red LEDs, and the blue one is noticeably
brighter than the other ones. In fact, it is so
bright that it makes me feel uncomfortable
looking at the Tone Beast when it lights up,
especially in a dimly lit environment!
In Use
Apart from this minor criticism, the Tone
Beast has proven to be a very reliable
and versatile preamp over the course of
the review period. It takes some time and
effort to get used to all the nuances is has
to offer, simply because Warm Audio have
put so many features inside this box, but
thankfully the controls are clearly laid out
and the labels easy to read.
These days, ‘sonic colour’ is something
of a buzz phrase, and the character
that can be imparted by transformers in
particular seems to be in vogue. But while
Audio Examples
A number of audio files demonstrating the
tonal colours that can be achieved using
the Tone Beast can be found on the SOS
web site.
WW www.soundonsound.com/sos/
articles/nov13/warmaudiotonebeast-media.htm
182
the TB12 has all the ingredients typically
associated with such ‘colour’, such as the
transformers, Tantalum caps and discrete
op-amps, please don’t think that using any
of these options will drastically change
the sound in any given situation. In many
use cases these variations remain very
subtle, and will only be audible to the
critical listener. How much such nuances
entirely different units (not that I would
have expected this!), but like two different
sides of the same coin. One of them has
a more open, sometimes even slightly
harsh top end, while the other is noticeably
softer and rounder, and there are plenty of
shades in between these two poles.
No matter how you look at it, the Tone
Beast offers many means to fine-tune the
result and to adapt the character of the
preamp to the nature of the source being
fed into its circuits. For instance, some of
these features may be used with good
results to round off the edges of an overly
bright capacitor microphone.
The feature that I liked the most
isn’t even the most sophisticated of all
these options — but it certainly is the
most powerful, capable of turning this
microphone preamp into a hefty distortion
box. The vast range of the output pot
(which essentially goes all the way from
off to unity gain) ensures that there are
no gain-staging limitations at all. Not only
do the saturation and distortion effects of
the TB12 sound great in their own right;
“Its Gain & Saturation and Tone Control
sections can transform the preamp into
a saturation generator, with a sonic scope
ranging from extremely subtle coloration to
the wildest fuzz sounds.”
matter in the context of the full, final mix
will often be debatable. Mind you, I am
not saying this to question the concept of
the Tone Beast at all! I simply would like to
encourage you to listen closely and keep
in mind that when it comes to saturation
artifacts, less can sometimes be more...
The core sound of the Tone Beast is
a very present tone with a pronounced
upper mid-range. This is not untypical
for a preamp from the extended API
family. The 312 might not be the thickest,
richest-sounding preamp on earth, but
it is capable of delivering very tight and
solid signals which can cut through any
mix, and the TB12 certainly navigates in
these waters, too. The contrast between
the cleaner configuration (x18 op-amp
and nickel transformer) and its more
coloured counterpart (x731 op-amp and
steel transformer) doesn’t sound like two
November 2013 / w w w . s o u n d o n s o u n d . c o m
as mentioned before, the tonal changes of
the other options become more apparent
when the unit is being driven further into
the realm of non-linear amplification. Listen
Alternatives
Other manufacturers also offer preamps
based on API’s classic 312 topology. For
example, BAE produce the 312A lunchbox
module and single/dual-channel rackmount
units, and if you don’t need all the options
of the TB12, then Warm Audio themselves
produce the WA12. A few other mic preamps
offer switchable circuit topologies and
variable gain staging. The Universal Audio
710 Twin Finity preamp is a little more
expensive, but it offers blending between
valve and transistor amplifiers, and its two
gain stages can be driven into distortion.
Other preamps well known for their
saturation capabilities include the Roll Music
Systems RMS5A7 Tubule and Chandler’s
Germanium and Little Devil.
to the Minimoog example from the audio
files accompanying this article, and you’ll
hear how meaty and thick the Tone Beast
can sound, highlighting the sonic impact
of the output transformers. When they are
bypassed, the signal sounds rather hollow,
with a spectrum that reminds me more
of a square wave. With the transformers
engaged, by contrast, the signal gets
noticeably thicker, sweeter and more
valve-like, adding further to the massive
tone of this classic synth bass line.
The tone control section boasts
plenty of tone-shaping options,
such as the selection of alternative
op-amps, capacitors and output
transformers.
Conclusion
First appearances can be deceptive, and
that’s definitely the case here: one should
certainly not view the Tone Beast as yet
another microphone preamplifier. Rather,
it’s a sound machine that can be deployed
to great effect in many other areas of
audio production than the tracking stage.
For instance, I can conceive of this being a
very useful processor for sound designers,
and many people would find the TB12 a
useful processor during a mix.
While the Tone Beast cannot compete
with high-end devices in every single
aspect of its construction, it does
a surprisingly good job, and offers a signal
path that’s far more sophisticated than
one would normally expect at this price. Its
character as a mic preamp might not be to
everyone’s tastes (because I can’t imagine
any preamp being the ultimate solution
for all possible uses), but doubling as
a saturation generator it offers a vast range
of additional applications. These alone will
be worth the price of admission to many
people. It doesn’t matter which way you
look at it, then: the Warm Audio Tone
Beast offers plenty, considering its rather
comfortable price tag. ££ £549 including VAT.
TT Nova Distribution +44 (0)20 3589 2530.
EE sales@nova-distribution.co.uk
WW www.nova-distribution.co.uk
WW www.warmaudio.com
w w w . s o u n d o n s o u n d . c o m / November 2013
183
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This article was originally published
in Sound On Sound magazine,
November 2013 edition
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