Reply To: hardware questions (speaker output)

[Michael P. Flaga]

1) Correct.

2) Currently, connect GBUF and LEFT to the speaker and set the VSdsp to Mono, using the MP3player.SetMonoMode(1); command.

3) The data sheet states the Full Scale output swing is 1.85V across 30 ohms. This equates to 6mA Peek to peek. for a 30 ohm speaker, or 0.114 watts. The same watts put into a 8 ohm speaker would result in 0.95 v peek to peek at 120mA. Approximately. Not sure where you get the 5V 50mA, unless you are referring to your speakers max abilities. which would then be a 5V*50Ma = 250 mW or 1/4W. Well above the VS1053’s standard/default output.

Note. I will add shortly support for the SM_DIFF feature. This will allow as stated “3.0 volts can be achieved with +-to-+ wiring for mono difference sound.” Then You connect a speaker between LEFT and RIGHT, then set the SM_DIFF bit in the mode register. Not using GBUF or GND and get more power out of the VSdsp. The data sheet does not spec this mode of operation, but it rational to think it was measured across a 30 ohm speaker as the rest of the spec’s were. This would yield 300 mW which would then be just beyond your 1/4W speaker. Setting or limiting the volume to -2dB would then limit the max power to approximately 80% (of 300mW) to 230 mW. Which is below the 250 mW speaker.