ouput voltage of power amplifier tda2030
Yes, the voltage at pin 4 is slightly affected by the flow of current through (say) Q1. In effect Q1 boot-straps (or lightens the burden on) pin 4. There is negative feedback at play here so it may not be that obvious what happens...

When the current through R6 is enough to begin turning on Q1, Q1 starts to replace pin 4 as the major supplier of current into the speaker. However it can't replace pin 4 entirely because then there would be no signal dropped across R6 so, in effect, pin 4 supplies just enoguh current to the speaker to get a big enough voltage across R6 so that Q1 can supply the main body of current required by the load.