[Logistics]

I have this old set of desktop speakers which are run by a TDA2007 based amplifier. The design is a little different than other tiny amps I've seen because it includes potentiometers not only for Volume, but also for Bass and Treble. I was wondering what the transistors in the design may be for, though.

If I follow the traces back from the Input+ pins, they first meet a capacitor, the likes of 2.2uF, probably just a decoupling cap, but then the trace meets a C945 transistor. After that it's a mess of resistors going every which way. Some tie to ground, others seem to run to one of the potentiometers, while others eventually meet the Voltage supply pin.

What are these transistors doing?

 

[Bjornboy81]

I guess the obvious answer would be for amplification (current amplification to be more correct). This would be your preamp stage. They are probably set up as an emitter follower (google).