Looking at the manual for the Model 20 it looks like the speaker jacks on the turntable/amp are RCA phono jacks. The plugs should be available at Radio Shack or on eBay. The manual, if you don't have one, is available here: https://www.hifiengine.com/manual_library/klh/twenty.shtml. You have to join to download but it's free and easy.