I built it. In both worlds. It works pretty well. Green is the output, blue is the speaker voltage, orange is the audio input.
Here is the list of components needed with some notes on why.
Transistors -> 3904, 3906
Diodes-> 1n4148
Trim pot -> 20k
Normal pot -> 50k
Caps -> 470uF Electrolytic
Aux cable -> Steal it from your friend
Speakers -> 8 ohm 1/2 Watt
Phone -> Audio input
Phone charger -> 5v (put a cap on it)
1 hour to build -> Get your shit together
Build notes: I didn't need to dc block the audio. It made zero difference [1]. Needed to cap the noisy 5v source. Tuning the trim pot helped a lot (7.54k). Just connect the PNP base thats connected to the source to ground, amplify about 10 to 50x then check the voltage on the output. If the voltage is too high or low (relative to ground) turn the trim pot till she outputs 0v. (The trim pot is adjusting the DC offset of the amplifier while the normal pot is for amplifying)
Why two 8 ohm speakers? Because surround sound... or no wait.. stereo? (Obviously 4 ohm speakers would work if you got them.. and yes its single channel)
Sounds like shit? Turn down the amplifier. You can honestly hear the sound fine without any voltage amplification. Turn the volume up on your phone to reduce noise / dc offset from the amp.
Why diodes? The push pull converter is efficient but sounds like someone left the world's largest fan on because of the transition between push and pull.
Alright im ready for the criticism. Lets see what you got
References
[1] Ears
