Manley TNT MICROPHONE PREAMPLIFIER - Manual (Page 15)

Any particular tips using the NT channel?
T echniques specific to the solid-state side of the TNT
are not daunting. Most likely the first thing to get
your attention will be the LED metering because it
is a bit unusual. The two bottom LEDs show the first
few stages of the preamps or what is going on with
the stepped gain switch, but BEFORE the Gain Trim
knob. The top two LEDs show that Gain Trim Knob
and the final output.
The bottom GREEN LED shows “SIGNAL
PRESENT”. The RED LED above it shows when one
is beginning to distort the preamp or the 60’s - 70’s
circuit. So use this RED LED to help set how much
“OVERDRIVE” and a typical setting makes that LED
flash about 50% of the time - but trust your ears - too
much overdrive may be hazardous to one’s career as
an engineer. You can’t undo mic pre distortion.
The top two LEDs are for the final output and the
Green LED is intended to show a good level to your
converter and the RED LED is intended to indicate
probable A to D converter overload. Originally we had
that RED LED indicate when the Preamps began to
clip, but they tended to stay dark, so now they just help
set a level for the next piece in the chain.
A good starting point for the 11 position GAIN switch
is “counter-clockwise” and the GAIN TRIM should be
set at roughly 12:00 or straight up. Turn up the GAIN
switch until you are getting a good level. You might
use the 4 LEDs on the TNT. The first or bottom is a
“signal present indicator” and lights up about 20 dB
below optimum levels. The second from the bottom
LED shows clipping in the first stages and follows
the GAIN switch, but is before the GAIN TRIM pot.
In normal clean operation this LED shouldn’t light
up and is typically ‘skipped’. Where it will come in
particularly handy is if you are operating the preamp
to deliberately over-drive it by turning down the GAIN
TRIM pot and turning up the GAIN switch. It should
be kept in mind that this won’t be easy in CLEAN
mode, but it becomes quite easy in 60’s and 70’s
modes. An interesting sound is when that second LED
is just occasionally flashing in the 60’s/70’s modes, and
the distortion is subtle, and creates a psycho-acoustic
effect of “character”, “richness”, and a 3D effect.
When that LED is glowing steadily, the distortion
should be pretty obvious. The LEDs are designed to
flash on both positive and negative peaks, and slowly
fade. A lot of peaks are too fast to see when the LED
directly displays peaks and the fade gives some clues to
the duration and musicality.
The top two LEDs are set to show output levels at
the output jacks. These are factory set up for +14 dB
and +20 dB over our standard +4 dBm, so they are
technically at +18 dBm and +24 dBm. Most A to D
converters are set up for +16, +18 or +20, so those
two LEDs should get you to a reasonable starting
point and give you a pretty good idea when clipping
is likely. Of course, you really do need to watch those
A to D meters, or tape machine VU meters as the final
judge, especially when you have processing between
the preamp and recording device. However, if need
be, there are internal trims for the LED thresholds, so
one can set up the LEDs for particular needs. It might
be noted that there is no LED to indicate when the
TNT clips – because it clips at over +30 dBm which
is probably higher than 98% of the gear it might be
driving. It seemed more useful to indicate where the
next device is likely to run out of headroom, besides
using the TNT for its own overdrive effects is covered
by LED #2.
If you tend to want the Cool Channel to be generally
your “clean preamp” and intend to use it as a reference
especially for acoustic instruments, then you might
want to consider using the 1/4” output as the main
output because the output transformer is not in that
path. And keeping it clean, you may want to leave the
“IRON” knob set at 12:00 or straight up. Turning the
knob either counter clockwise or clockwise introduces
some subtle transformer color. Now if there is another
transformer down the chain in another piece of gear (or
even a magnetic tape recorder), the counter clockwise
settings may help minimize it’s contribution. You
might be able to use the 60’s - 70’s switch if you keep
the Input OL (overload) LED off by keeping the Gain
Switch lower and the Gain Trim higher or near its max
of +10 dB.
If you want the Cool Channel to be multi-tinted then
maybe the XLR output should be your choice. Then
experiment with all the preamp’s controls keeping in
mind that moving a microphone by a few inches might
affect the color more, maybe a different mic might be
more significant a variation, and once you hit “record”
the player’s tone and volume usually change anyway.
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