Comparing two preamps uses our Audio Control Center, in particular our models 457 and 460, and optionally the remote control unit which is model 458. Real-time comparison simply means you can switch back and forth between the two preamps 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 460 with a short stereo cable and then connect two of the 460's stereo outputs to the two preamps to be compared. Use the "PHONO" preamp input connectors if the music source is a turntable or the "LINE IN" or "AUX" input connectors for other sources. The stereo output of one preamp goes to stereo input #1 on the 457 (the connectors are on the rear panel). The stereo output from the other preamp goes to input #2 on the 457. Finally, connect the 457's output #1 to your power amp's input. You can switch between inputs 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.