Filter tweak for digital backwash?

As my system improves, it’s easier to hear anomalies. The search is now on for a tweak to filter only digital backwash in my AC. The culprit is the regulated transformer power supply (120vac/19vdc converter) to the dedicated laptop for streaming.

The balanced power conditioner has separate outlets for analog and digital. The digital outlets already have built-in filtration for backwash. They work well. But, I need even more. When the laptop is running on its internal battery, the music is very smooth. Unfortunately, the battery life is short. When the laptop is running on the power supply, there’s a slight stridency. When the power supply is plugged in anywhere else, there is huge stridency. So, I’m looking for some gizmo to clean up the digital backwash in-between the conditioner digital outlet and the power cord to the regulated power supply.

I’m not looking for an overall line purifier. The balanced power conditioner does a pretty good job already. Any suggestions?