Recording audio path, which occupies its own printed board, is far more complex. There are three electronic level controls, wired in series. Continuously variable fade-in and fade-out is performed by an analogue transconductance amplifier. Signal levels at the input of Dolby encoder ("recording level") and at its output ("tape sensitivity") are controlled by 8-bit multiplying DACs. Finally, a CMOS multiplexer, coupled to a low-Q bandpass filter centered on 4 kHz, selects the desired mid-range equalization setting. Yet another set of 8-bit multiplying DACs, coupled to a non-defeatable Dolby HX Pro circuit, sets the desired bias current. Dolby dynamic biasing, according to Stereo Review, improves treble saturation levels by about 6 dB.
