Step 9

    The remaining connections all are soldered to the DB-25 female solder type connector. The table below is used to match up the solder holes on the perf-board to the solder pins on the DB-25 plug.

    If you have never soldered to a DB-25 plug before, the easiest way is to tin the wire well and then insert it into the DB-25 solder slot and hold the soldering iron to the slot. The solder on the tinned wire will melt and make the connection.

Step 10

    Before the IC is inserted for the final step, be sure to use the Ohm meter to check the connections to the DB-25 plug and the audio plug. If there are no ground faults and everything checks out then finish off the project by inserting the 4558 Op-Amp as shown in the illustration.

    With the project completed all that is required is to give it one more double check and pack it into a nice looking enclosure.