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Power amplifier design

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gogu_biologu

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I've recently built a power amplifier for my computer, but i have a lot of noise on 12V line.

Any idea to remove it?
 

IanP

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Use common mode (both lines, +12V and GND) suppression chocke rated for at least 2A dc and inductance ≈1mH and after it combination of capacitors:1000µF/100nF.

regards ..
 

ronyutp

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If the noise is still there you can add an small resistance in series with inductance, calcultate the resistance for a 0.5 volt drop. This resistance will transform your noise in heat. But you will loose some little amplifier output power.
 

baza

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i think both solutions create problems.

1. we can't make a ground with the soundboard, because we'll short-circuit the
-12V ( ground ) coil.
i've tested it with a big primary coil of a transformer, and 10.000uF capacitors, and it doesn't work when the supply current of the amplifier is low.

2. the "filter" gamma with a resistance is worse, so the supply voltage for the power amlifier will be in function of the level of the input signal. ( that's not good!!)

The best solution is to built an linear power supply with a transformer ( very big ), and to supply the amplifier.

A good solution will be:

a. to built a SMPS, to obtain about 16-18V from 12V
b. After SMPS insert a linear regulator, like LM7812, followed by 1000uF/100nF capacitors ( last should be ceramic).
 

yeechyan

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Which 12V line are you mentioning about? Is it the 12V line from the PSU of the computer? The PSU is a switching voltage regulator instead of linear regulator. Maybe the switching causes the noise in the 12V line?
 

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