Arduino UNO audio output with R2R DAC

Question

I'm trying to implement audio output using R2R 8bit DAC and Arduino UNO.

This is my hardware: https://i.stack.imgur.com/WeNPf.jpg

This is the sound i want to hear: http://vocaroo.com/i/s0VDwBBkQRdc

This is a wav file, 16Khz, mono, 8 bit pcm.

I used matlab to retrieve the binary data from the wav file, and then wrote this code:

http://csharppad.com/gist/0f39da965e31fc838c6de73ff50e5669

I connected the output to some speaker and what i hear is some strange sound..do you think i miss something in my hardware/software?

Thanks!