Op Amp Stereo Amplifier Results

This circuit does not use any input biasing resistors, or even something simple such as a voltage divider bias using two resistors. The reason for this was to minimize cost, hence if you need more stability in the circuit then it is possible to add these components. The stability of this circuit depends upon many factors such as the input impedance of the signal source, the signal level, the output loading of the headphones, battery power level to the circuit, quality of build, quality of the components used, decoupling capacitors, and much more.

I suspect some equivalent 741 packages will perform better than others will. The CA3140 is a BiMOS version of the 741 with a FET input that has very high input impedance. That chip should perform better and provide greater closed-loop stability.

The 3F07 Audio Jack Socket came from eBay at a cost of ten for £1.30. For the headphones, I am using a rare vintage pair of 1980s Sony headphones that produce a great sound. This project was very useful for understanding operational amplifier stability and bias requirements. It also makes one appreciate all of those dozens of resistors usually used at the input section of commercial amplifiers, nevertheless, this is an experiment one has to experience.

Headphone Socket

Output

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