In our audio system with 3 ADAU1701 the HISS noise level is very high.
HISS noise level of 3ADAU is much large compare to single ADAU,
and our board with single ADAU has same HISS noise level
as Evaluation Kit of Analog Devices.
Also we use single crystal for all the three IC's,
ie Crystal output is fed to MCLK1 of 1st IC and from XOUT of 1st IC,
connected to MCLK pin of 2nd and 3rd..
Please help us solve this problem...