Humming Sound From DAC

[Noak]

hi all,

I've a DAC which uses the following path:

Coaxial Input -> 74HC04 -> CS8416 -> AD1852 -> Amp+Buffer Stage

Recently, after making modifications to the power supplies, no audio sound can be heard from the output, instead, I can only hear a consistent humming sound.

I've checked all power supplies and they are supplying the correct voltages all the ICs above.

I've replaced the 74HC04 and all the opamps at the amp+buffer stage and the humming sound persists.

The CS8416 is able to lock onto the incoming SPDIF signal and the mute pin on the AD1852 is working as well, although these in general, don't imply that the CS8416 and AD1852 are working fine.

Can anyone suggest where that humming sound might come from?