Noise in LM3875? Help!

bee696 · 10th December 2005, 09:55 AM

Hi All,

I just made a LM3875 amplifier (using standard non-inverted circuit, Ri=680ohm. Rf=20K, filter cap = 1000uF).

I measured the output using multumeter (DC= 0.147, AC = 6mV). Seems not bad? However, when I connected it to speakers, I heard some noises (white noise), how can I solve it?

Besides, everytime I turn off the amp, a big "pop" sound? pls help!

Nordic · 10th December 2005, 11:49 AM

you wil need to draw or describe the grounding scheme you used if you are to get any specific advice...

janneman · 10th December 2005, 01:05 PM

Quote:

Originally posted by bee696
Hi All,

I just made a LM3875 amplifier (using standard non-inverted circuit, Ri=680ohm. Rf=20K, filter cap = 1000uF).

I measured the output using multumeter (DC= 0.147, AC = 6mV). Seems not bad? However, when I connected it to speakers, I heard some noises (white noise), how can I solve it?

Besides, everytime I turn off the amp, a big "pop" sound? pls help!

How's the hiss with the input shorted?

Jan Didden

10th December 2005, 09:55 AM	#1
bee696 diyAudio Member Join Date: Jul 2005 Location: Thailand	Noise in LM3875? Help! Hi All, I just made a LM3875 amplifier (using standard non-inverted circuit, Ri=680ohm. Rf=20K, filter cap = 1000uF). I measured the output using multumeter (DC= 0.147, AC = 6mV). Seems not bad? However, when I connected it to speakers, I heard some noises (white noise), how can I solve it? Besides, everytime I turn off the amp, a big "pop" sound? pls help! __________________ Bee696

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10th December 2005, 11:49 AM	#2
Nordic diyAudio Member Join Date: Sep 2005	you wil need to draw or describe the grounding scheme you used if you are to get any specific advice...

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