Audio Characteristics: Alinco DR-1200T
This is the receive frequency response of the Alinco. Note the strong low-cut filter below 500Hz. I believe that this response in is intended to filter out PL tones so that there's no annoying "hum" when using continuous tone squelch. It's interesting to find this characteristic in a radio that's supposedly designed for packet radio use.
The de-emphasis above the low frequency turning point is reasonably close to 6dB per octave, and the 5.55dB rolloff from 1200 to 2200Hz is only about 1/2 dB more than ideal.