> 4.7 | Stereo Headphone Concept

> To use the modules’ balanced speaker output together with different other signal sources (e.g. MP3 stereo source) the following concepts are suggested:
> Figure 21: Circuit concept for stereo headphone - sample 1
> EPP1/EPN1 and EPP2/EPN2 are used for a simple gain switch mechanism that can be used for switching between speakerphone and handset mode. U1 converts the balanced signal into an unbalanced one. This unbalanced audio signal is split into speaker and headphone amplifier (U3 and U4). U3 can play back GSM sound as well as mono sound from any other source. Figure 22 offers a similar flexibility as sample 1 but is less complex. The disadvantage is the need for bigger electrolytic capacitors.
> Figure 22: Circuit concept for stereo headphone - sample 2