A test assembly includes a printed circuit board, a first subsidiary test chipset, a second subsidiary test chipset, and a main test chipset. Specifically, the vertically oriented FET includes a channel region, a source region and a drain region. The output device mixes the audio signal component having the frequency characteristics corrected with an audio signal of the right channel and an audio signal of the left channel to generate mixed output audio signals, and outputting the mixed output audio signals as a right channel output audio signal and a left channel output audio signal.