Art Project Series User Manual page 7

CONNECTIONS
A. Left and Right "Combo" jacks on the front allow for either
XLR or ¼-inch TRS input connections.
The connections are used for instrument or line level balanced
or unbalanced signals. The high fixed input impedance works
well with guitar and other passive instrument pickups. You can
use an unbalanced or balanced plug with this connection. The
XLR connections are used primarily for balanced microphone in-
puts.
Pin 2 is positive, pin 3 is negative, and pin 1 is ground.
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