I'd like to modify this circuit (output stage of a digital audio synthesizer) because the signal going into the headphones amp (TPA6111A2) is too low, probably because of the passive filtering before the potentiometer. With such low signal, I'd need a really large gain (about x150) to get a good audible signal on the output, but using that much gain I'm getting excessive noise and distortion on the output (the TPA6111 datasheet suggests a gain range of 0 to 20).

The signal balance between the two paths joining at thee potentiometer wiper, and the frequency response, is spot on with what I want, but I'm wondering if there is a way to modify the filters to reduce their passband attenuation without altering balance and frequency response, so that I can use a lower gain on the final stage.

The signals labelled as OUT-x are digital square waves (3.3V) outputs from a microcontroller. I guess the two transistors Q2 and Q19 are providing some form of distortion/waveshaping (that I'd like to keep). The amplifier is also mixing another signal via C20 (still to be defined).

Also, I assume all the circuitry on the bases of the two transistors could probably be simplified (it came up like this from experimenting)