Linear Tube Audio UL+ Instructions Manual page 7

The back panel of the ULi+ features the IEC connector, power
switch, tape in, tape out, four pairs of RCA inputs, one pair of XLR
inputs, two pairs of RCA subwoofer outputs, and four binding posts.
Inputs
There are five total inputs: four RCA stereo pairs and one stereo
XLR pair. The XLR input provides a tube-coupled balanced input.
The preampfification stage converts the balanced input into a
single-ended signal that suffers no voltage loss. The ULi+ also
features the possibility of adding an optional MM/MC phono
preamplifier. For more information regarding the operation of the
phono preamp, please refer our website or to the additional
Phono User Guide included with your ULi+.
Outputs
The speaker outputs use binding posts that allow you to use
banana plugs, spades, or bare wire. There are two headphone
outputs: one "HI" and one "LO". These refer to the output power,
not the impedance. Use the HI output for full-sized headphones
that need more power and the LO output for more sensitive
headphones. Each uses a 1/4" jack. There is a switch to use either
the headphone outputs or the speaker outputs. Volume level is
independent for speaker and headphone outputs.
The ULi+ also features an additional preamp-level SUB OUT which is
step-attenuated. This is a unity gain op-amp coupled, stereo RCA
preamplifier output meant to be used with low-pass filtered, active
subwoofer RCA inputs. The Sub Out is menu configurable for
Stereo, Mono or Mute. The Sub Out is automatically switched off
when the output switch is set for headphone operation.
Tape Monitor
When Tape Monitor is selected via the button on the front panel,
the selected input sends an unattenuated signal directly to the
Tape Output and the ULi+ outputs the signal from the Tape Input.