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by mansr 4505 days ago
When the Samsung ARM Chromebook came out, people quickly found that careless tinkering with alsamixer caused the speakers to overheat and melt the case as a result of being driven with a high DC current. A driver update blocked the control causing the damaging signal routing.
3 comments
userbinator 4505 days ago
They didn't bother to put $0.001 DC blocking capacitors on the DAC outputs? This isn't a "bug in the kernel" or any software, it's a clear hardware flaw.
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fnordfnordfnord 4505 days ago
Be fair, those caps are easily two or three times that much.
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userbinator 4505 days ago
In relatively low quantities, yes: http://www.digikey.com/product-detail/en/CL05A105KP5NNND/CL0...

But when you're buying them in quantities that a company like Samsung would (that above link is, amusingly enough, to ones that Samsung themselves make), the price drops off rather steeply. $0.001USD is around what I can find for buying them from China in 100Ku.

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fnordfnordfnord 4505 days ago
I left the reply in jest. But while we're here. Capacitors vary widely in price by type, capacitance, and quality. A 1uF multilayer ceramic is probably one of the most common and cheapest to buy capacitors there is, except maybe the .01uF. Output coupling of an audio amplifier requires a lot more capacitance than ceramics can muster. That cap, if present is going to be an electrolytic, and it is going to cost more than $0.001 or even $0.01 at qty. Although I'm reading that direct coupled amplifiers are all the rage these days, probably so they can get the expensive electrolytics off the BOM.
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userbinator 4504 days ago
I have the schematics for my laptop and it has 1uF ceramics on the speaker PA inputs, that's why I linked to that particular one. The other common values I've seen are 2u2 and 4u7, which is a little more expensive but will give more bass --- not that it really matters on a tinny little laptop speaker anyway. At least I'm happy to know that I won't burn out the speakers on my laptop with DC.
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orik 4505 days ago
I never realized they fixed that! What great news!
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tmzt 4505 days ago
Do you know what kernel version or distribution fixed that? I've avoided installing a native distribution for that reason.
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