- It should operated a a frequency that is well-beyond the audible range and several times beyond the highest Sampling Rate used within the DAC
- ALL High-Frequency circuitry should be separated from / isolated from / shielded from any sensitive Analog Output-Stage circuitry
In the end, however, methinks that it would be easier to prevent "cross-contamination" from Linear sources where the highest frequency being introduced is the Primary Line Frequency and any harmonics of that.
Either way - do what Mr. Pass did with most of his Pre-Amps:
Keep the higher-Voltage stuff in a SEPARATE, shielded enclosure and keep it away from any sensitive analog circuitry. There's nothing like DISTANCE to keep Mutual Inductance at bay...