User`s manual

4
CONNECTIONS:
The female XLR Input jack is used primarily for balanced microphone input. Pin 2 is positive, pin 3 is
negative, and pin 1 is ground. +48 Volt phantom power is supplied to pins 2 and 3. If you are using
the XLR input with a balanced line level signal or a microphone that does not require phantom power,
make sure that phantom power is turned off. The XLR Input impedance is switch selectable from the
front panel. Maximum gain from the XLR Input to the XLR Output is 70dB. This input can handle very
hot microphone signals up to +16dBu before clipping.
The ¼” Input jack is for instrument or line level unbalanced signals. Its high fixed input impedance is
ideal for guitar and other passive instrument pickups. Plugging into this input bypasses the micro-
phone preamp circuitry for a cleaner signal path. Make sure you use a mono unbalanced plug with
this connection for proper operation. Maximum gain from the ¼” Input to the XLR Output is 50dB.
When the Gain control is at minimum, this input can handle hot signals up to +17dBu.
The male XLR Output jack is active balanced with pin 2 being positive, pin 3 negative, and pin 1 is
ground. With an output impedance of less than 300 Ohms and a maximum output level of +26dBu it
can provide a hefty balanced signal for long cable runs. Normally you would use this output to go
directly into a power amplifier, recording system or a mixer’s balanced line or insert inputs. Though
we do not recommend it, if you have to go directly into the balanced microphone input on a mixer
make sure that phantom power is off at the mixer. The mixers input pad and level controls should be
set for minimum gain, and the output control on the TUBE MP Project Series with USB should be set
at a low enough level to prevent overdriving the mixers input section.
The ¼” Output jack is unbalanced and has an output impedance of 600 Ohms. It can be used to
send signals to an amplifier, processor, line input on a computer, or any unbalanced input. The output
level is 6dB less than the XLR Output and the slightly higher output impedance makes it a better
choice for driving into more sensitive inputs like on an instrument amp. Since it can still put out up to
+20dBu, the Output control should be set at lower levels when driving sensitive equipment.
The power connector on the rear should only be connected to the power supply that comes with the
unit. 9 to 10 Volts AC @ 700 milliamps is required typically. Make sure that you specify AC and not
DC if you have to replace this supply. Internal circuitry converts this power to the higher voltages
needed for the tube and phantom power sections.