PreSonus EQ3B - Manual (Page 22)

PRESONUS
The EQ3B can be connected to an insert point on a console
(mixer) by using a TRS Y-cable. This cable is Y-shaped, has a
single TRS ¼” jack on one end and two ¼” TS (Tips-Sleeve) jacks
on the other end. The single end will look like a stereo ¼”
connector jack. This end of the cable plugs into the insert jack on
the mixer channel. The other ends of the cable plug into the input
and output of the EQ3B. If the EQ3B does not work immediately,
you may want to try changing the jacks that are plugged into the
input and output of the unit.