Manley TNT MICROPHONE PREAMPLIFIER - Manual (Page 13)

THE COOL CHANNEL
Solid State or Right Channel
The No Tubes side of the TNT gives you a range of
colors and might even be considered a contrast to the
Tube side. Or maybe not. If one has strong ideas that
tubes and transistors sound vastly different then the
TNT might be a little unsettling. For what it is worth,
both the Tube side and Solid State side of the TNT are
pretty clean representatives of their technologies.
On the other hand it is extremely easy to find a variety
of “personality preamps” using tubes (we make a few
too) that all sound different from each other. Similarly
there are many different solid state or discrete sounds. It
largely depends on topologies, parts choice (especially
transformers), and a variety of other choices a designer
might make (or a cloner might copy).
As a “clean” preamp (CLEAN setting and IRON
set fully counter-clockwise) we think the TNT Cool
Channel may be hard to beat for sheer transparency
and lack of electronic artifacts, especially in the 300
and 600 Ohm impedance settings. It is also designed
to be useful as a fuzz-box or distortion device (60’s
or 70’s setting, INPUT GAIN hot, GAIN TRIM fully
counter-clockwise). It won’t simulate a Marshall
stack or analog tape with VU’s buried deep in the red,
but it shares some of those characteristics and might
be an alternative sound, and at least sounds better
than most preamps driven hard. Or it can give you
a range of subtle flavors just as a basic preamp with
the IMPEDANCE and IRON knobs, and/or by using
the 60’s & 70’s settings, but driven lightly and before
obvious distortion. These colors are set up to be easy
and obvious to use, even though they are for the most
part subtle. In fact, considering that this is really just a
Mic Pre, and not a compressor or EQ, it seemed most
appropriate to not go overboard and make it into an full
blown processor, but rather give the user more control
than is usual yet keeping it within a ‘safe’ realm where
it is unlikely one will screw up a recording doing
something that can’t be undone. That ‘subtlety’ might
be obvious in the IMPEDANCE switch, that unlike
other preamps that may have a 6 dB gain change from
one setting to the next, and again, the TNT is designed
to have maybe 1 dB of gain change from one extreme to
the other, with most mics. We consider this important
for selecting which impedance to use. Alternatively,
comparing settings with radically different volumes
makes the process near impossible to do especially
when the differences tend to be subtle.
The IRON control may also be subtle in many situations
because it uses the actual output transformer (which
starts off pretty good) rather than a fake simulation
just labelled to suggest a sound. The IRON control
practically removes all audible effects of the real
output transformer in the “0” setting and that can be
easily verified by comparing the ¼” transformerless
output to the XLR transformer output.
Just a little note on the subtleties of the Impedance and
Iron controls: Maybe other units have more dramatic
changes when you adjust similarly labelled controls
and maybe what you are hearing then is flaws in the
implementations or parts they use. We try not to do
that, and we won’t con you and we did put some effort
into maintaining constant levels as these controls are
adjusted. We also try to maintain similar frequency
responses when impedance is changed, where others
don’t. So the TNT knobs do what they say they do, and
don’t add strange misleading effects (for a change).
The NT preamp starts as 3 gain stages. 2 are identical
and symmetrically used for opposite phases (XLR pin
2 and pin 3, i.e., balanced) and are voltage amplifiers
like 99% of all mic preamps. Unlike 99%, these voltage
amplifiers are very high impedance (2 meg Ohms) and
exhibit very low capacitance and inductance, not that
microphones need or are designed for that light of a
load, but occasionally there are audible benefits. The
third initial gain stage is a transformer input current-
mode amplifier, which might be considered a rare
technology in a mic pre and nearly opposite to the
voltage amplifier topologies. These 3 preamps are
variously selected and combined with the deceptively
simple IMPEDANCE switch. Rather than a resistor
that just shorts out the signal for lower Z, that resistor
feeds the current mode amplifier in the TNT, and the
part of the signal that is normally thrown away is
amplified and mixed back in.
On the IMPEDANCE switch there are 5 positions.
Furthest counter-clockwise is the “300C” setting , and
next is the “300” setting. What is the difference? The
“300C” position is only the current mode preamp by
itself. The “300” setting uses both the current mode
and the voltage mode preamps and is closest to a good
50/50 blend. The next setting, “600”, restricts some of
the mic’s signal from going into the current stage and
more is available for the voltage stage, and the blend is
closer to 30/70. The 2000 Ohm setting and the 2 meg
settings only use the voltage preamp.
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