Those tiny oscillations are just the tubes’ own life force – a bit like breathing in a vintage engine. If you’re restoring a radio meant to sound “authentic,” let that hiss stay; it’s part of the character. If the audience prefers a cleaner tone, tweak the bias or replace the old tube with a newer equivalent, but don’t strip away the history just for a quieter hiss. It’s a classic trade‑off between fidelity and flavor.