I’m working on a kit which will allow the internal speakers to continue working and provide a line level (not amplified) output for a powered speaker. The kit will include a new base plate and pad.

The plate is plastic. The echo requires 15VDC.

It is 15.27 Volts Measured with no load. It will be 15 +/-. Remember connect nothing that you have not measured the output of in advance. Good luck.

Suggest this from AMAZON

You get a few extra pieces you won’t need for this but perhaps your next project. There are may others to choose from. Choose wisely.

Middle Pin always positive.