DigiTech DIGIDELAY Manual page 11

Connections
The DigiDelay has a single input and a pair of outputs. Out 1 is used if
the DigiDelay is being connected to only one amplifier. Out 2 is used
for stereo operation. Connect Out 1 to the first amplifier and Out 2
to the second amplifier. Using Out 2 gives you ping-pong delay for the
first three Mode settings, or Tape or Reverse delay types.