まともなリニア電源の例
台湾メーカーだが
Keces P8
https://www.audiophonics.fr/en/hifi-power-supply/keces-p8-ultra-low-noise-regulated-linear-power-supply-5-7v-9-12v-4a-p-13654.html

ちょっと高いが海外で評価が高い
UpTone Audio
JS-2 Linear Power Supply
https://uptoneaudio.com/products/js-2-linear-power-supply

電源由来のノイズ対策なら同じメーカーの
UltraCap LPS-1.2
https://uptoneaudio.com/products/ultracap-lps-1-2