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The ABX Tester Module allows you to switch between two stereo inputs to determine if you can perceive any difference between them. For example, you could use the Processed and Unprocessed outputs of the Bit Reducer Module, and see if you can tell any difference between a double-precision floating point signal and one which has been quantised down to 16 bits.
The module defaults to ‘Monitor Mode’, where you can audition the two input signals at will. There are two stereo inputs, A & B. You can select which signal is passed to the stereo Output jacks by pressing Input Selection button A or B. In Monitor Mode, an LED above each button shows which input channel is currently selected. You can also choose the “Mute” button, which silences the output.
When you are satisfied that you can tell a difference between the two signals in Monitor Mode, you can switch to ‘Test Mode’ by pressing the ‘X’ button. This will select Input A or Input B at random and send the signal to the Output jacks. However, the Input Selection LEDs are blanked so that you cannot tell visually which channel is currently being heard.
You must choose one of three options to return to Monitor Mode:
- Press Test Answer A button if you believe that you are hearing Input A.
- Press Test Answer B button if you believe that you are hearing Input B.
- Press the Pass button if you are unable to tell which input you are hearing.
In all cases, the module will return to Monitor Mode and the Input Selection LEDs will indicate which input was heard during the previous test. If you made an explicit choice of Input A or Input B, your result will be tallied and displayed in the Test Results Panel. If you chose ‘Pass’ instead, then your result is not tallied and you simply return to Monitor Mode.
The Test Results Panel keeps track of the number of tests you have run and the number of correct answers you entered. The Tests and Correct seven-segment LED counter displays can record up to 99 each. The red Reset button in the middle resets both the Tests and Correct counts to zero and returns the module to Monitor Mode. The test status text below the counter displays (“10 or more tests required”) provides an indication of the statistical significance of the current test run.