A simple, powerful amplifier for a room and requires a minimum number of components. It is stereo and the components can be supplied from component recoveries. It works effortlessly at first and the result is a pleasant one. The sound generated by the stereo amplifier is pleasant and without much distortion! The amplifier has very good performance.

   Basically, the entire configuration is a symmetrical Class A amplifier that incorporates an input filter, a driver stage and a symmetrical power output in the component of which is the versatile 2N3055 or TIP3055 transistors.

   This amplifier can provide up to 2x100W on 4 ohms, being able to amplify the signal received from any audio source including mobile phones.

Circuit description:

   At first glance regarding the power floor we will tend to believe that it is not a symmetrical configuration because the two 2N3055 power transistors are both NPN.

   However, we can see that at the beginning of the circuit we have a symmetrical differential preamplifier formed mostly by transistors Q1, Q2 and Q3, Q4.

The bias current must be set to 50 mA with RTRIM3/RTRIM4 as follows:

- Disconnect the speakers and short-circuit the input terminals (zone J1)

- Connect the multimeter (set to current measurement) between the positive terminal of the power supply and the positive terminal of the amplifier.

- The adjustment is made until the value of 50 mA appears on the multimeter screen.

- Disconnect the multimeter, remove the strap from the input and you're done.