This bridge power amplifier, without great pretensions, is simple to perform, and works with a single power supply of 18 V. It is based on the use of two amplifiers type TDA2003, capable alone to deliver a power of about 10 W (10% distortion, limited to 7.5 W at 0.15% distortion) .
Mounted in bridge amplifier these two circuits can deliver the Honourable power of 40 W with an 2 ohm headphone. Using a 4-ohm headphone will still release a power slightly greater than 20 W. The bandwidth extends from 40 Hz to 15 KHz, and power ratings are valid for a harmonic distortion less than 0.15%.
This bridge power amplifier circuit requires a voltage of 18 V maximum and should not be exceeded. While the system supports a higher voltage (up to 28 V) output, but the symmetry is no longer guaranteed, so it is not possible to get more power with 18 V, without distortion. Note that you can also choose to supply low voltage, 12 V, for example, if you just need a little power and does not require a power of 40 W.