Radial Engineering Ltd.
PowerTube™ Preamp
True to the Music
®
3
MAKING CONNECTIONS
Before making any connections, start by turning off your audio system and turning all
volume levels down. This helps protect equipment from turn-on transients that could damage
loudspeakers and other sensitive equipment. We recommend using a power bar with an on-
off switch as this makes it easy to turn on and off the 500 series rack, monitors and so on,
using a single switch. Carefully plug the PowerTube into your 500 series rack making sure
to avoid exessive stress on the card edge connector. Screw the module in to ensure it does
not accidentally get dislodged.
Your microphones can connect to the PowerTube via the front panel XLR jack or at the rear
panel of your 500 series rack. Connecting the PowerTube output is done at the rear panel.
Most 500 series racks are equipped with XLR connectors. When you plug the PowerTube
into your 500 series rack, it will automatically route the input and output to the module and
connect 48V phantom power. With the Workhorse, this is augmented with ¼” TRS connectors,
D-Subs and a signal to feed the Workhorse mixer. Using the PowerTube with the Workhorse
also activates the Omniport. With the PowerTube, the Omniport turns into a DI input for high
impedance instrument pickups.
Connect your microphone to the PowerTube using a standard 3-pin XLR cable. You can use
either the front or rear panel XLR as the input - both are wired in parallel. The PowerTube
follows the AES standard with pin-1 ground and pin-2 hot. Most devices are wired this way
but older vintage equipment should be checked to confi rm compatibility. To ensure the lowest
noise always use a high quality balanced cable from a reputable manufacturer.
-20
-2
-10
-4
-6
+1 +2 +4 +6
MIC INPUT
TRIM
OUTPUT LEVEL
Radial
-60
dB
0
dB
POWER
TUBE
GAIN VU
dB
0
NORMAL
48V
INVERT
OMNIPORT
:
INSTRUMENT INPUT
HPF
GAIN
+60
dB
+35
0
dB
f
AIR
5kHz
80Hz
FRONT PANEL
MIC INPUT
INPUT
OMNIPORT
FEED
LINK
1
OFF
OFF
CARD SLOT 1
OUTPUT
OUTPUT
INPUT
REAR PANEL INPUT
(WORKHORSE)
INPUT
OUTPUT
REAR PANEL INPUT
(500 SERIES RACK)
Depending on what type of microphone you are using, you may or may not need to engage
the 48V phantom power. This is designed for condenser microphones. If you are using a
dynamic microphone or ribbon microphone, leave the phantom power off. The switch is
recessed as a means to prevent accidentally turning it on which could harm some ribbon
microphones. An easy to see LED indicator tells you if phantom is on.
Connect the XLR output on the back of your 500 series power rack to your recording
system so that you can audition the PowerTube. We recommend that you fi rst listen to the
PowerTube without running it through other audio signal processors until you have had a
chance to familiarize yourself with the sound and functions. Using your own voice to test is
always best as it really gives you a familiar starting place.
