LM3886 components

[454Casull]

I'm planning to air-wire several LM3886 chips, but the typical application schematic shown on the current datasheet differs from the one that's shown in chipamp.com's assembly manual for their LM3886 kit. Which one should I get components for?

http://www.national.com/ds/LM/LM3886.pdf

http://www.chipamp.com/docs/lm3886-manual.pdf

[MJL21193]

This one revision B.

[454Casull]

Much appreciated.

[AndrewT]

fig2 revB needs RF attenuation added.
C2 (22uF) is far too small.
C2>=1.4 * C1 * R1 / R4
>=1.4 * 3.3u * 22k / 1k >=102uF
Try 100uF or preferably 150uF.

[MJL21193]

Originally Posted by AndrewT

C2 (22uF) is far too small.

It's the value National recommends. How much difference do you think it makes?

Originally Posted by AndrewT

fig2 revB needs RF attenuation added.

And the ones from National and Chipamp don't?
I'm not saying it's a bad idea (rather, a good one) but I haven't seen it on any LM3886 schematic.

[Redshift187]

Originally Posted by MJL21193

And the ones from National and Chipamp don't?
I'm not saying it's a bad idea (rather, a good one) but I haven't seen it on any LM3886 schematic.

Actually it's on almost every National schematic as Cc. Did you check the "optional" external components description?

In addition, C2 creates a roll-off at a certain frequency. You can customize this frequency to have less effect on the audio by changing the value. The optional external components description gives the formula.

[MJL21193]

Originally Posted by Redshift187

Did you check the "optional" external components description?

Yeah, no, I didn't look that far down...my laziness showing up (again).

Still, I have built many without the RF protection and I have used 22uF for the feedback cap. I don't think it would make an audible difference with regards to the feedback cap value, as long as it isn't too low.

This are minor issues (non existent IMO) and it seemed that Andrew wanted to nit-pick.