Manley TNT MICROPHONE PREAMPLIFIER User Manual
Page 23
COOL CHANNEL IMPEDANCE SWITCH RELATIVE LEVELS
Microphone Output Impedances
The middle horizontal line suggests a range of typical microphone output impedances. For exam-
ple, many mics are approximately 150 ohms, so for those, changing the TNT Cool Channel Imped-
ance switch alters the level by 2.5dB going from the highest setting to the lowest. If you have
other preamps with an impedance control, you might be used to much bigger level changes plus
strange tonality changes. You might be accustomed to that preamp’s design flaws.
With the TNT, changing the Impedance switch tends to be subtle. Worst case would be very low
source impedance which corresponds with 4 dB gain change across the five Impedance switch set-
tings. Best case would be 200 to 600 ohms mic output impedance, which corresponds with 1-2 dB
gain change across the five switch settings.
With some mics like FET condenser types, expect very little tonality change. With ribbon mics
or dynamic mics, one can alter some aspects of their damping. However, it will be the mic itself
changing and sometimes mis-loading its output transformer rather than switching the preamp’s
input transformer into the technical twilight zone...
23
-5
-4
-3
-2
-1
0
1
2
3
4
5
0
50
150
250
600
2M
2K
600
300
300C
-3 dB
+3 dB