Hello to all. My knowledge of circuits and power amplifiers is quite limited from an academic standpoint. The PCB board schematic that arrived from China is something I'm attempting to sketch. Furthermore, I am unable to understand the OP-Amp Section.
It makes sense if JP1's pins 2 and 3 and JP2's pins 1 and 2 are connected, but what about JP3? Single Jumper in the left channel. What does R83 accomplish?
JP1 and JP 3 will be a potentiometer?
Would you mind giving me some opinion on this, please? that your advice would be helpful to me with this endeavor.
Thanks
opu
It makes sense if JP1's pins 2 and 3 and JP2's pins 1 and 2 are connected, but what about JP3? Single Jumper in the left channel. What does R83 accomplish?
JP1 and JP 3 will be a potentiometer?
Would you mind giving me some opinion on this, please? that your advice would be helpful to me with this endeavor.
Thanks
opu
Attachments
Seems this is for optional configuring the stereo amplifier for a mono bridged output.
Some general background info:
https://sound-au.com/project14.htm
Some general background info:
https://sound-au.com/project14.htm
R83 sets the gain of U1B to -1 and ensures the two power amps (L and R channels) receive input signals that are 180 degrees out of phase (for bridge mode). The gain is -1*(R84/R83) with the minus denotes inverting. You should not alter this value or fit a pot.
For bridge mode it seems you link pins 1 and 2 of JP2 and use the right channel input socket as the only input to the amp. U1A has a gain of -1 (calculated as -1*(R81/82) and so feeds the now inverted input signal into the right channel power amp via linking pins 2 and 3 of JP1.
The output of U1A also feeds U1B via R83 and that sets the gain of U1B to -1 as described earlier. So the output is U1B is inverted with respect to U1A and this signal is fed to the left channel input by linking JP3 pins 2 and 3
So you now have the two channels fed with antiphase signals suitable for bridging.
For normal stereo use you feed the two input channels directly into the power amps JP1 and JP3 pins 1 and 2 linked. Setting JP2 and linking pins 2 and 3 grounds the opamp input and effectively removes it from the circuit. If you left JP2 pins 2 and 1 connected you would feed signal into the opamps and even though the outputs are now not connected in purist terms it is not the best thing to do, far better to have no signal on the opamps that could couple via stray capacitance etc to other areas.
