PowerTube™ Preamp
True to the Music
®
Radial Engineering Ltd.
4
GETTING STARTED
Although the PowerTube is extremely easy to use, we suggest you follow these simple
instructions before using it. As with all audio equipment, always ensure all levels are turned
down or equipment turned off before making any connections or plugging the PowerTube into
a 500 series power rack. This common practice ensures turn-on transients will not damage
more sensitive components such as tweeters.
There are two rotary controls on the PowerTube named TRIM and GAIN. Start by setting
the TRIM control to 12 o’clock and the GAIN all the way counter-clockwise to the minimum
setting. Make sure the polarity invert switch is in the normal (out) position and turn off the AIR
and HPF controls by also setting these to the out position.
TRIM
-60
dB
0
dB
NORMAL
48V
INVERT
HPF
GAIN
+60
dB
+35
0
dB
f
AIR
5kHz
80Hz
Start point:
1. Set the TRIM control to 12 o’clock
2. Make sure the 180º is off (switch outward).
3. Gain control should be off (fully counter-clockwise).
4. HPF should be turned off (switch outward).
5. AIR should be turned off (switch outward).
Plug in your microphone. If you are using a dynamic microphone, you are set to go. If you
are using a condenser, you will likely need to turn the 48V phantom power on unless it is
equipped with an internal battery. Using a tweaker or small screwdriver, turn on the phantom
power by pushing in the recessed switch. The LED indicator will illuminate when on. The
switch is purposely recessed to protect older ribbon microphones from accidental turn on.
Turn up the GAIN control until it gets to a relatively low listening level. Testing at low levels
prevents accidental damage to sensitive components due to turn on transients and of course
reduces opportunity for feedback. Test by reducing the GAIN control and increasing the
TRIM so that you get a sense of the dynamic range and a feel for how the PowerTube
controls work. You will fi nd that the range is quite extensive and that even when you drive the
PowerTube into the red, it will still sound relatively clean.
