Headphone Volume Knob; Headphone Output - Universal Audio Volt 476 Hardware Manual

A microphone is typically connected with an XLR connector, and an
instrument or line level signal is connected with a ¼" (6.35 mm) TS or TRS
plug.
Preamp gain and impedance automatically adjusts for line or mic signals,
based on whether the plug is XLR or ¼", along with the state of the INST
button.
Press the INST button to toggle the impedance and gain of the line input to
accommodate a Hi-Z instrument, such as an electric guitar or bass.
Tip: The Vintage Preamp and 76 Compressor can be used on mic, line, and
instrument inputs.
BALANCED AND UNBALANCED CONNECTIONS
The line inputs on Volt are balanced when connected with TRS
•
connectors to balanced equipment.
Use TRS (balanced) audio cables for the best results with
•
balanced audio sources. Balanced equipment uses three
conductor wiring (via TRS or XLR connectors) to reduce
interference and electrical noise, and to provide better audio
quality over longer cable runs. Use TS (unbalanced) cables for
instruments that are not balanced, such as an electric guitar or
bass, or an unbalanced synth or sound module. TS connections
may also be suitable for shorter input cables, where electrical
interference noise may not be an issue.

(2) Headphone Volume Knob

Adjust the headphone volume with this knob. The headphone volume
control is independent from the Monitor volume control.
Note: The monitor output and headphone signals are the same.

3) Headphone Output

Connect stereo headphones to this output. Headphones are connected
with a ¼" (6.35 mm) TRS plug. If your headphones have a ⅛" (3.5 mm) plug,
use a TRS ⅛" to ¼" adapter.