Up2Stream I2S connection to Wondom amp - audio heavily distorted when in WiFi mode

I have connected anUp2Stream mini to the I2S port of a Wondom AA-AB32256 Amp. When I stream from bluetooth, I have good sound quality, but very heavy distortion when I use the Wifi mode. Also the automatic voice is heavily distorted. The distortion is on both channels and can also be heard when listening to the line output on the Up2Stream mini board.

Thinking that the problem was something to do with grounding or the power supply I physically disconnected the amp from the power supply. I still got a distorted sound on the line output.

However, when I disconnected the i2s cables to the - powered down - amp, the distortion disappeared (cable was still connected to the Up2Stream board). Reconnecting the cable brought back the distortion.

I am now totally flummoxed and have no idea how to proceed. Can anybody help here?

I have managed to solve the problem.

Eventually I suspected that the I2S inputs on the Wondom amp were capacitively loading the output from the Arylic board too much (better said the output from the wifi module).

I inserted a 74HC126 (powered with 3.3 V) between the Arylic board and the Wondom amp to buffer the I2S signals (including MCLK) and I was able to stream undistorted audio.

Thanks. I will bookmark this solution.