I buy 6j1 preamp in lazada, I test it to classD mini amplifier and the output is terrible humming background on music. here is the simplest way to eliminate the hum:

replace C2-C6 with higher farad capacitor for smooth DC, range 4700-10k uf. 50v
R1 -3.3ohms 5w
47k is optional. (input to ground)

please like and share the idea :) thanks!
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