Next to test is bare naked I2C DAC from unknown to me chinese manufacturer. It is advertized as (not really) direct replacement of TDA1311 DAC ond partially its successors TDA154X series. It requires output driver and i added one using 4558D opamp according to dtasheet application circuit

Data format: left justified, stereo output

Ouput: high-impedance, biased, requires output driver

Price: ~€0.10-0.20 per unit

Clearly it is here because the price, and it is not expected to have hifi performance, but rather support low-cost audio driver in projects.

Here is the setup. 

Only element added to above is output 1uF cap to filter out DC.

Again, I only have toy oscilloscope, therefore results will be eye measured:)

Test signal is mono wav file generated by esp8266 module using ESP8266Audio library modified for LJ format, industry standard 44.1Khz sampling rate. 

1KHz on the output, after driver

2KHz after driver

10KHz on the output, after driver

20KHz on the output, after driver

As you can be seen, already at 10Khz distortions are huge, and 20Khz is a mess. However up till 20Khz there is no fading out of signal, and despite harmonic distortions i expect it to sound quite nice (for the price). As i said before, this is bad candidate for Hi-Fi sound, but very promisiong chip for less demanding audio applications. I keen to see it in action.