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Use of LM324 in audio circuit


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I am planning to design a simple 5 to 6 inputs audio mixer with an output of around 300mV at 1kHz with an input signal of about 0.6mV. Supply voltage is around 12 to 18V DC. I intend to use the commonly available LM324 quad opamp. Is there anybody in the community who has used this IC for such audio purposes? What are the pros and cons of using this IC? I have heard that the LM324 is not suitable for audio work; but since it is freely available and very cheap, and since the mixer is not going to be a high end equipment, can I use it safely? Any help would be gratefully accepted. Thanks to all in advance.
C.M.

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I used the LM358, which is the same thing except that it has two opamps instead of four and it works well. I built a preamp and a stereo width controller (which is actually a channel mixer) using this IC.
If you want lower noise then use the TL074.

The power supply must be regulated and within the limits specified in the datasheet.

I have heard that the LM324 is not suitable for audio work

It's not suitable for Hi-Fi because of the THD and the noise.
but since it is freely available and very cheap

The TL074 is cheap too, but not as cheap as the LM324.
can I use it safely?

Of course... if you have a schematic that works.
Just avoid ground loops or you'll get weird noises.

You can find the datasheets and download them here http://www.datasheetcatalog.com
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The old, old, old LM324 quad and LM358 dual are the first low power opamps ever made. They made them low power by making the output transistors operate in class-B intead of class-AB so they have crossover distortion unless they drive a DC-biased load.
They also made them low power by reducing their speed. They deliver full output up to only 6kHz.

You want a gain of 500. An LM324 or LM358 individual opamp has a frequency response to only a little less than 1kHz with the gain so high. The noise will exceed the signal with a gain so high.

The TL071 single, TL072 dual and TL074 quad opamps are made for audio with low noise, extremely low distortion and have full output up to 100kHz. Their power supply doesn't need to be regulated.

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  • 3 weeks later...

I have used the LM324 in many audio applications in the past. For the specifications that you have given, this chip will be fine. It will not give you really great results that you would get with a newer low noise op-amp. But it will give you a descent mixer. Especially at 1 KHZ.

MP

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