lm3886 output network with coil or not?

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I am reviewing which LM3886 kit / assembled unit to buy. There is confusion on the output design.

In the datasheet's test circuit's output network has a 0.7uH coil parallel with 10Ohm resistor.

I go through LM3886 boards, only a few have this network. Most boards doesn't have the coil.

Is the coil and required? And the effect on audio quality?

Thanks.

http://www.ti.com/lit/ds/symlink/lm3886.pdf
Page 5
 
I remember a post in this forum said using pure air coil only. If wrap copper wire around a resistor may risk the saturation of the resistor.

No.

The question that should have been asked by now is.....what type of speakers are you going to attach to these amplifiers? The impedance load might make your decision for you.

Generally, you could do without the LR circuit on the output since it's purpose is to decouple capacitive loads. Typical speakers would not cause the amplifier a problem (with that condition.)

The RC Zobel network is useful to terminate the amplifiers into a defined resistance above the audio band. Typical speakers MIGHT cause the amplifier a problem in this instance since they become inductive at high frequencies and would unload the amplifier.

However, it wouldn't hurt to use both networks on the output. A fairly bullet-proof implementation is the PM21 amp from Marchand.

(Take note of the photograph with wire wrapped around the resistor to create the L/R combination.)

PM21 Dual Audio Power Amplifier Module

http://www.marchandelec.com/ftp/pm21man.pdf

Hope that helps.

Dave.
 
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