Negative part of Line level audio waveform clamped
Should I connect 0V to GND instead of 2.5V?


Yes, of course. Otherwise you risk a dead short from your 2.5 V source to 0 V if there is a ground return path anywhere in your system.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. The audio signal can be decoupled from the DC with the addition of a series capacitor. The capacitor blocks DC whilst allowing audio to pass through. A 10 µF capacitor should do the trick. Watch polarity.