ProtoDAC TDA1387 X8 project

[hifinet]

That sounds good for the I2S resistors (430R or 470R works, maybe even down to 120R, but I haven't tried). I think the I2S resistors attenuate reflections and noise on the I2S lines. Without them, it can sound like an AM radio barely tuned into the station. A lot of noise with music in the distant background. Test that it will convert bitrates up to 384k.

The I/V of 429R should work with most of the modules. Some modules with higher output might clip at 0dB. As the power supply voltage increases, the output current of the module (and voltage at the I/V resistor) increases, so you will want to keep the power supply voltage close to 5.0 VDC. 

As far as the C3/C4 decoupling caps, you will need to listen to them and see which ones you like best. The Panasonic FR-A that I like are 1000uF and ESR of 41 mOhm (EEU-FR1A102L Digikey part P14378-ND ).

In my experience, when the capacitance is too low, dynamics and bass worsen. When capacitance is too high, the soundstage (depth) flattens.

When the ESR is too low, the sound is very accurate with large soundstage, but intolerably gray and sterile sounding.  Too high and the soundstage collapses.

Please share your experience.