It's the cascade of 5 Sallen Key Low Pass filter with the following cut frequency and selectivity:
1~ f = 3,972kHz ; Q = 0,627
2~ f = 7,526kHz ; Q = 1,318
3~ f = 11,08kHz ; Q = 2,444
4~ f = 13,74kHz ; Q = 4,723
5~ f = 15,02kHz ; Q = 15,12
This low pass filter is very selective! Due to this its specific application is Hi-Fi audio filter: this is 'cause the ripple of the gain in pass band is very little (±0,25dB).
The resultant cutoff frequency is 15kHz.
We have the following attenuations:
• -3dB @ 15,20 kHz
• -50dB @ 23,40 kHz
