OKTO Research DAC - AES/EBU noise

If you’re using an OKTO Research DAC Pro with our ISP and are facing some digital artifacts or weird sounds in your speakers, it could be that the OKTO Dac is not well configured.

Here’s what OKTO Research provided us with as a solution:

The origin of these artifacts or digital sound can be caused by overly strict jitter eliminator settings in the Sabre DAC.

This can usually be resolved by increasing the "DPLL BW AES" value, which controls the bandwidth of the DPLL in the jitter-eliminator of the Sabre DAC chip. Starting from firmware version 1.6, this option is accessible via the dac8 PRO Menu > Advanced > DPLL BW AES.

For older firmware versions, you can access this setting through the Developer menu by following these steps:

1. Enter the dac8 PRO's menu and navigate to Volume.

2. Set the volume of channels 6, 7, and 8 as follows:

   • CH6 volume = -7dB

   • CH7 volume = -3dB

   • CH8 volume = -1dB

3. Navigate back to the main menu, where the Developer menu will now be visible under the Status menu.

4. Enter the Developer menu and adjust the DPLL BW AES parameter to a higher value to check for any improvement.

5. Restore the previous levels in the Volume menu.