When making an battery-powered amplifier out of a wooden box, is it necessary to include a ground other than that coming out of the negative side of the battery?
Do some of you fix a piece of metal in the box and also ground to that? Does it need to be a big piece of metal?

Has anyone created nice builds without a chassis ground?

Has anyone solved a buzzing or problem by installing a chassis ground?

Please let me know, and thanks for any input you can provide. The amp in question will be powered by a 9 volt battery and is a build with two bridged LM386s chips.

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No extra metal ground plate, etc. is needed in those style amps. Just be sure of continuity between the jack neg., the battery neg., the speaker neg., volume pot, and the two pins of the LM386 IC that are to ground. In most of those, it is the 2 and 4 pins. But on the bridged pair of LM386, it may be different.

One note: with two LM386 chips bridged, a single 9 volt battery will drain rather quickly. The one bridged IC circuit I have seen suggested using a regulated 9 volt adapter (wall wart).

I have been building single LM386 amps for years, and have not been inclined to go with two chips. The singles sound great when matched with a good speaker (easy and cheap to find at a thrift store). I also add a line out switch and jack, so the amp can drive an external 8 ohm speaker. This one has a 6 inch speaker in a large wine box. I have it's twin, with an 8" speaker.

And this is the circuit I have used. Easy and works well. To add a line out feature, just send the signal from the negative side of the 220uF capacitor to the center pin of a DPST switch. Then each of the outer two lugs to either the speaker, or an ext. jack.

Thank you very much for your reply and the diagram! I was hoping this was the case. I've done a few single-chip amps, so am looking forward to seeing how much oomph bridging two chips will deliver. It was hanging in the back of my mind: "You've never done a chassis ground. Maybe you need to," so I appreciate hearing from someone with a lot of experience!

The "oompf" will more likely come from speaker selection and the choice of box. Smaller boxes are nice and all. But without the extra surface area offered in a larger box, the next best thing is having the line-out option so you can drive an actual speaker cabinet. I have a pair of vintage stereo speaker cabs (one in my shop, the other in my room) that measure 18"w x 12" deep x 30" tall, each with a 10" 35 watt speaker. That small 1/2 watt amp sounds huge through them, with full range of tone.

Best luck with the dual chip. I look forward to hearing how it sounds.


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