DIY cheap MP3 player using arduino nano (or uno)

Hello! I am started build mp3 player, but arduino mp3 shield its too much expensive. I have sd card adapter for arduino already, can i do cheaper mp3 decoder plate with normal sound quality?

Probably not. The memory and speed to decode MP3 files is not available in an Arduino Uno.

MP3 needs several kbytes of RAM, which is far more than the entire RAM of Arduino Nano/Uno.

The algorithm operates on blocks of 1152 samples, and merges data with the prior 576, so memory to hold at least 3456 bytes of audio data is pretty much essential. Any practical implementation would need to hold at least 1 incoming frame, which is 1045 bytes at 320 kbit/sec rate with 44100 Hz sample/sec output. The MP3 algorithm also defines a "bit reservoir" buffer to allow input frames to contribute data to future frames, which means the input buffer must be somewhat larger.

OK! so i need to use additional more powered 5v mp3 decoder ? can you recommend me something chip with normal sound quality ? I think am also need amplifier for normal stereo mode.

can you recommend me something chip with normal sound quality ?

Do you mean some chip or something cheap? If the latter what do you call cheap?

I think am also need amplifier for normal stereo mode.

That goes without saying.