crivoli Posted May 12, 2006 Report Share Posted May 12, 2006 I have built the following circuit but the sound quality is terrible. Any ideas on how to make the sound quiality MUCH better?I am using an electret mic and an 8 ohm speaker. Thanks Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 12, 2006 Report Share Posted May 12, 2006 You don't say any parts values.You don't say which IC you used.Your sketch doesn't have power for the electret microphone.If you used an opamp then that is your other problem. An 8 ohm speaker needs hundreds of milliamps. An opamp provides a max of only 20mA. Most opamps should not have a load less than 2k ohms.For a little clear power then use an LM386 power amplifier IC. Quote Link to comment Share on other sites More sharing options...
crivoli Posted May 12, 2006 Author Report Share Posted May 12, 2006 I am using 1K resistors for Rb, a 1M resistor for R2, a 1K resistor for R1, a 10uF cap as already seen, a .47uF cap for the coupling cap from the mic to the IC, a LM741 IC and a 68uF cap out of the IC to the speaker....Sorry for not posting the specs Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 12, 2006 Report Share Posted May 12, 2006 A 741 opamp will have high distortion when driving an 8 ohm speaker with an output power more than only 1.6mW because its max output current is only 20mA. 250mW from a power amp IC into 8 ohms is a peak current of 250mA.The 741's high frequency response will drop above only 200Hz when it has a gain of 1000.The 68uF cap that feeds the speaker will reduce low frequencies below 400Hz.So your "amplifier" doesn't have any power, doesn't have any high frequency response and doesn't have any low frequency response. No wonder it sounds terrible.An LM386 is a small power amplifier IC that will produce about 300mW with low distortion into an 8 ohm speaker with a 9V supply. With its gain at 20 then its frequency response with a 1000uF output capacitor is flat from 40Hz to 150kHz. With its gain at 200 then its high frequency response drops above 15kHz. Quote Link to comment Share on other sites More sharing options...
crivoli Posted May 13, 2006 Author Report Share Posted May 13, 2006 I switched over to a LM386 design from the datasheet and it works like a charm.I appreciate everyone's advice VERY MUCH!!Thanks again Quote Link to comment Share on other sites More sharing options...
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