I have built this little kit for a class AB Amplifier. This is the schematic if you do not want to follow the link
It works fine, I can hear decent sound.
I then tried to check the output with an oscilloscope to learn a bit more. I am using a bitscope micro USB oscilloscope. I have replaced the speaker with 5 47 Ohms resistors in parallel to cope with the load. The voltage peaks match what I get in LTSpice, but I was a bit surprised to see the straight lines on the descending and raising part of the wave.
This is for a 50mV peak signal @ 1kHz (the maximum allowed by the design). The clipping is obvious when I increase the signal, and the strange behaviour is still there even if I halve the signal to 25mV.
The device is also a function generator. This is what the input signal looks like (100mV sine wave).
Do you think it is because of the oscilloscope limited sampling or some kind of distortion?
Solution (I think) The answer from bobflux made me think that problem was in the quality of the signal. If you look at the signal trace you can see that there is a lot of noise.
The solution was to introduce a 10/1 voltage divider (10K/1K) and increase the input signal to 1.1 V. This creates a beautiful sine wave (although it is seems a bit attenuated).