Plecto
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It is common for 'pops' to occur - transients occur with the initial current in-rush, and with the transformer [on/off]. There are circuits which delay the turn-on time [to the op-amp]
Your circuit works from a dual-polarity supply so there are no capacitors to charge. I do not see any output capacitors that might not be needed.
Your resistor values are very low so the coupling capacitor values are very high and are not even high enough for passing low audio frequencies.
If you use 47k for R15 and R16 then the coupling capacitors can be 0.33uF (330nF film type) and they will pass 10Hz and higher. For low input offset voltage then R6 and R16 should also be 47K then the feedback resistor values also must be 47 times higher. The values of C7 and C8 can be reduced.
Perhaps you are using non-polarized electrolytic capacitors that "store" (dielectric absorption) a charge? That would cause a thump. Film capacitors do not do this.
Your schematic shows a +/- 5V supply but since you are using a 15V-0-15V transformer the DC supply will be about +/- 20V.
The opamp does not have enough output current to drive the power transistors to a high level.
I was talking about the COUPLING capacitors C1 and C4 that MUST NOT be polarized electrolytic type. Also the FILTER caps C7 and C8.
Since you have 9.1k for R15 and R16 then the values of the C1 and C4 coupling capacitors must be 1.7uf for -3dB at 10Hz (flat down to about 50Hz) which is a pretty big and expensive film capacitor. That is why I recommended 47k ohms and 330nF.
I know about the main DC filter capacitors but 4700uF is not marked on your schematic.
How on earth will the opamps produce enough output current to drive the power transistors?? Oh, your speakers have an impedance of 100 ohms or more?
EDIT: I know. The part numbers for the output transistors are also wrong. You are actually using darlington transistors with a high current gain to drive low impedance speakers.
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