Complementary pair - Role of capacitor on emitter

Question

I bought this little kit for a class AB amplifier.

The second stage is quite clear (and typical), but I am struggling to understand the role of capacitor C2 on the emitter branch in the first stage. In the explanation they say that this is a "complementary pair in common emitter mode". However, I would expect to see the two emitters connected and either no capacitor or a capacitor as a bypass. This looks an open circuit in DC.

I also built an LTSpice model to check the voltages and it looks like it is being used to keep the base of Q1 at Vcc/2 (approximately).

I have looked around and could not find any other similar example.

Am I reading the circuit incorrectly? Just learning about electronics and amplifiers just for my own education, so please bear with me.

Answer 1

I am struggling to understand the role of capacitor C2 on the emitter branch in the first stage

If I redrew it like this (where capacitor C2 is removed), does it make more sense: -

In other words: if you swapped the positions of C2 and R3 in the original circuit, you would see a DC voltage of about 9 volts across C2 (half of the 18 volts DC supply).

Q1 is acting as a differential input device where the base is the input signal and the emitter is where the feedback signal goes. A more sophisticated circuit might use a differential pair amplifier instead but, this will work reasonably well.