The MP3-TF-16P Module. ... then it’s recommended to include a 1K resistor in series with the RX pin of the module. Recommended input voltage (Vcc) for the module is DC3.2V to 5.0V ... Arduino Sketch ...

If our example resistor ended in gold (orange, white, black, gold), its 39 Ohms value could be five percent higher or lower. For a possible minimum of 37.05 or a maximum of 40.95.