LM1875 Amplifier Watts

Hi audiguru thanks for your comments.

Yes in the amp kit it was fed from both channels,again I missed that coupling part in my drawing.
Now I corrected.

It is fed from two 4.7K.Note that C4 capacitor is 104.

Today I'll increase the gain in the first amp in sub section.But even now (didn't increase the gain yet) I cannot put the bass level half way mark its plenty of bass.

I noticed the LM1875 subwoofer amplifier (not mentioned in the drawing) has set the gain to 70.Its feedback resister is 39K & the resistor goes to ground is 560R.

(39k/560R)+1 = 70.Is this too much!!

Audioguru please wait I spotted another mistake give me 5 mins

I spotted out the two satteleite amps gain is set to 70.Which is too high.I have marked the dividing resistors value which is there.

I think increasing that to 2.2K will give low wattage compared to subwoofer amp.

So here is my final calculations

Satelite amps gain (39K/2.2K)+1 = 18.72
Subwoofer ams gain (39k/560R)+1 = 70

I changed the resistors R17 & R27 to 1.8K.The satellite gain decreased tremendously.But still the ratio between sub & satellites isn't match.Now the satellites is too low.

New gain levels

Satelite amps gain Each (39K/1.8K)+1 = 22.6
Subwoofer ams gain (39k/560R)+1 = 70

Suraj143 said:

I changed the resistors R17 & R27 to 1.8K.The satellite gain decreased tremendously.But still the ratio between sub & satellites isn't match.Now the satellites is too low.

Click to expand...

That's how you want it, then you simply adjust the bass level control to make them match.