Comparing two power amplifiers uses our Audio Control Center, in particular our models 457 and 459, and optionally the remote control unit which is model 458. Real-time comparison simply means you can switch back and forth between the two power amps using the same music source: CD player, turntable or whatever. Connect the components as shown in the diagram using stereo RCA cables. Since this is not a permanent setup, just arrange the pieces fairly close together on a table or where ever is convenient.

Connect the music source to the model 457's stereo input #1 (on the rear panel). If the music source is a turntable, you will need to connect a preamp as shown in the diagram. The diagram shows three power amps being compared because the model 457 has three switch-selectable outputs and the model 459 also has three stereo inputs. To compare two power amps, just leave the third output on the 457 unconnected. The thrid input on the 459 is also unconnected. You can switch between outputs 1 and 2 using the rotary switch on the 457's front panel, or optionally, you can plug the remote control unit into the 457 (on the rear panel) and then use the switch on the remote control. Using the remote control has the advantage that you can sit in a comfortable listening position when doing the switching between preamps.