Dumb Question About LM386s

[Paul Marossy]

So on the Little Gem, there is a 220uF series cap on the speaker positive terminal, which is for DC blocking which is basically per the datasheet. OK, I get that. But on the Little Gem MK2, it's a bridged amplifier and there are no DC blocking caps. I have also seen this arrangement on the LM380 datasheet - no caps shown with the connections to speaker. So why is this? Do the two sides theoretically cancel each other as far as DC is concerned?

[FiveseveN]

In bridged configuration, both terminals of the speaker are connected to an output, which should be at the same DC potential.

[Paul Marossy]

In bridged configuration, both terminals of the speaker are connected to an output, which should be at the same DC potential.

OK, makes sense. And what if they aren't exactly the same?

[samhay]

https://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers



If you power your amplifier with a single (cf. bipolar) supply, the outputs will typically be at about half supply.
Almost all amps that do not use coupling caps on the output will have some DC offset, including bridged amps. The larger this is, the more power the speaker will have to dissipate. If you have 1V offset (which would be pretty unusual), this will be 1/8 W into an 8R speaker.
Probably not a big deal, especially when one expects the offset to be likely to be 10's mV.

[PRR]

> what if they aren't exactly the same?

You. Bike. Water. Camera.

Say 150 pounds total. But 5 pounds water on one handlebar, 3 pound camera on other handlebar.

Like Sam says, the un-balance is usually unimportant.

[Paul Marossy]

> what if they aren't exactly the same?

You. Bike. Water. Camera.

Say 150 pounds total. But 5 pounds water on one handlebar, 3 pound camera on other handlebar.

Like Sam says, the un-balance is usually unimportant.

More like 175 lbs total, but I get your point.