Last edited:
#101 The four resistors are 15ohm and 10W each which I wired two in series for 30 ohms and then the two sets of 30 ohms are wired in parallel to give a total resistance of 15 ohms. These get extremely hot and burn about 30W at idle. Yes, Class-A amplification is very inefficient. I burn over 20 Watts to get only about 4.8 audio Watts per channel!
I spend a few hours listening to my favourite songs on my new amplifier, that is, the class A TIP41 based amplifier I connected up. Amazing. The initial impression of distortion disappeared, and I could hear sounds I had not heard before.
I replaced the initial small output transformer with a large one from a PC speaker power supply - the large heavy old ones, and sound improved, was louder. Bass is lacking possibly due to the input capacitor of 470 uF. After a few hours the 9V battery went down to 6.86V and is still playing. Next step is to hook up an AC/DC adapter.
I plan to get an output of 1 Watt so 4 Watts to get 1 Watt still is more efficient than using a 35W amplifier after all, for the same level of enjoyment.
I replaced the initial small output transformer with a large one from a PC speaker power supply - the large heavy old ones, and sound improved, was louder. Bass is lacking possibly due to the input capacitor of 470 uF. After a few hours the 9V battery went down to 6.86V and is still playing. Next step is to hook up an AC/DC adapter.
I plan to get an output of 1 Watt so 4 Watts to get 1 Watt still is more efficient than using a 35W amplifier after all, for the same level of enjoyment.
I cleared out the distortion in the audio output by changing the input capacitor from a polarized 470uf electrolytic capacitor to a 1uF non-polarized electrolytic capacitor. The value of the capacitor is very low, so it must be cutting off all low frequencies. Rolling them off.
So it does work after all, and with low or acceptable levels of distortion. Time to build a circuit and an enclosure and create an amplifier.
Polarized vs Non-Polarized (NP) electrolytic capacitors | All About Circuits
So it does work after all, and with low or acceptable levels of distortion. Time to build a circuit and an enclosure and create an amplifier.
Polarized vs Non-Polarized (NP) electrolytic capacitors | All About Circuits
Testing continues, with the large output transformer and the proper capacitor. I moved on to using an AC/DC adapter with 4.5V to 9V settings and the music plays loud enough, with a lot of dynamism, even harshness.
Apparently I have got the circuit right because replacing the TIP41 with the 13003 transistor resulted in the same level of sound, and the transistor did not get that hot either. Hearing sounds I have never heard before on familiar tracks.
Apparently I have got the circuit right because replacing the TIP41 with the 13003 transistor resulted in the same level of sound, and the transistor did not get that hot either. Hearing sounds I have never heard before on familiar tracks.