Following the first schematic, the one with r6 and c4, I believe it is the speaker return. And connect to star ground.
It is fixed now. I needed to separate signal and power ground.
You may also want to add a small (something in the 10's of picofarads range) capacitor in parallel with your feedback resistor R3. This will compensate for high frequency oscillations. You'll notice the sound get a lot smoother.
Start with 4p7 and increase from there. If you have an oscilloscope, put a square wave through it and if your square wave has a jagged edge increase the capacitance to 10pF etc, repeat until the output wave is as smooth as the input wave.
You can also do this by ear if you don't have a scope, just listen out for extended "sss's" when people sing or harsh high notes, when those become silky smooth, you've got the right cap value.
Start with 4p7 and increase from there. If you have an oscilloscope, put a square wave through it and if your square wave has a jagged edge increase the capacitance to 10pF etc, repeat until the output wave is as smooth as the input wave.
You can also do this by ear if you don't have a scope, just listen out for extended "sss's" when people sing or harsh high notes, when those become silky smooth, you've got the right cap value.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.