Yes, the device ground is pin 3. Ground is very confusing, and beginners who are not confused
by it have not yet thought about all this enough. Even the experienced may not be clear.
Check that the output DC (at pin 4, referred to ground) is about half of the power supply voltage.
This voltage is set by the 22k divider.
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We're talking about the output DC offset, it should be about halfway between Vcc and ground,
to allow equal swings on both halves of the waveform. That measurement is probably ok.
The signal gain factor is set by (R6/R5 + 1) = 21 (which is 26.4dB).
The two 22k resistors from Vcc to ground (R1 and R2) set the DC output voltage.
This is because the feedback circuit (R5, R6, C3) forces the DC output voltage to
be equal to the DC voltage at pin 1.
It really should be 10VDC for a 20VDC supply, but your meter may be loading the circuit,
or the resistors may be off. What's the DC voltage across C2?
We're talking about the steady DC voltage across the C2 capacitor terminals (no signal).
A capacitor can't conduct direct (DC) current, but it can hold direct (DC) voltage.
The voltage across C2 should be half of Vcc.
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Just got home now but its late. I wanna say thank you guys for trying to help! Will resume tomorrow. Sad news the pins of the LM1875 broke off... How are you suppose to fit them on the breadboard without force 😵 Still have the spare to work on and ordered two more. Just scared the spare will break on me now
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I have some information that can shed some light? Maybe the distortion is coming from the speaker because of the it's frequency response thats reacting poorly to the lower ones and some degree to the higher ones? Does that make sense? and I am using this speaker http://pdfstream.manualsonline.com/7/77d5788f-ce18-449d-8f1f-e55e0d99bcfb.pdf The Front ones (SC-F391 6 ohm)
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Through the OP-AMP rule right? V-=V+
Yeah in DC analysis R3 = Half of VCC, thus meaning Pin 2 & 1 = Half of VCC and Pin 4 as well.
What is your plan ultimately? Breadboarding is ok (just) for prototyping, but that isn't what you are doing if you are following the datasheet schematic. You can learn a lot just by reading. The chip is quite a good one and there are a number of tried and tested designs based on it.
To power my speakers back at home essentially. Also I am a theory guy so making the chip from the ground up will help me reinforce that.
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How about buying or designing a pcb to build it on? To be frank, using breadboard is asking for trouble
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