Maybe something interesting here 
For best quality, here’s the link to original schem pdf
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Schematic reminds me of a certain Jedi. The ADC0809 is rated for absolute maximum voltage -0.3 V to Vcc+0.3 V on its input and output pins. There’s nothing here to protect them.
In particular, presumably the audio in here is supposed to be in the 0–5 V range, not ±5 V, not only to stay within spec but to make it actually work over the full waveform.
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I knew by posting the schem that there would be some security modifications / improvements proposed, but it seemed to be a good basis.
I also saw that @Jos had posted a comment on the vid 
To bias the input signal you need not use an opamp. If you lift the input signal of the ADC using 2 resistors (one connected to gnd and the ADC-input, the other to the positive input voltage and the ADC-input) and feed the signal to their center via a capacitor you should be set
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Juanito More make recentely also a Bit Crucher module (no schematic for the moment)
Description :
Audio comes in to the circuit through an attenuating potentiometer and then an amplifier that will clip/saturate the signal at 5 volts peak-to-peak.
The next stage centers the audio signal around 2.5V, to take full advantage of the next stage, which is a ADC0820, which turns the audio level into an eight-bit number. The ADC0820 has an “interrupt” function that lets you send it a clock and basically lower the sample rate of the audio.
The bits then go to a pair of CD4066 quad bilateral switch ICs, which get their gates turned on or off with a comparator ladder that turns off each bitstream, starting with the least significant bit, up to the next-to-most significant bit (the MSB can always get through).
Then the bits get processed by another comparator ladder, with resistors between the outputs and the less-significant-bits down the ladder, so the values of the more-significant-bits get duplicated down the line – bitcrushers that leave their “crushed” bits at high-impedance state lose loudness as the bits get crushed, this one doesn’t (it gets LOUDER). Finally, the byte gets turned back into audio with a DAC0808 chip…
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