I am trying to build an audio amplifier for a 4ohm speaker with mono output. It will be running 24*7 so i need a power efficient amplifier with a standby function. So a class d is preferable as i read its the most efficient. please suggest a good amplifier circuit. i tried making a tda2030 and tda 2050 amplifier. but everyone said that they are not good.

 

Look at the Texas Instruments collection of Class D amps.
One of those may work for you.
How much power do you want?

 

One thread is enough for the same subject, please to visit Audio Amplifier design.