Here is how to make an adapter for using the Pasco Power amplifier (CI-6552A)with the analog output of LabPro on CH4.
Make the following connection on the adapter:
LabPro BTA pin #1 (furthest from the key) to the center pin of the 8-pin DIN connector.
LabPro BTA pin #2 (second furthest from the key) to the ground pin of the 8-pin DIN connector.
Note that on a 8-pin DIN plug, looking at the pins, with the notch at the top, the ground connector is the one at the 4:30 clock position. Go to https://www.vernier.com/probes/specs/pinout.html to see a diagram of pinouts.
(The easiest way to make one of these adapters is to take a CBL-8MC and change the #1 pin (usually white wire) to the center pin of the DIN connector.
Note that the Pasco Power Amplifier doubles the voltage.
Also, note that Vernier sells a Power Amplifier (PAMP), which comes ready to connect to either a Vernier LabQuest (any version) or LabPro.