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Old 5th November 2013, 08:55 PM   #1
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Default Necessary to use speaker protection in LM3886 gainclone?

I'm building a 2.1 gainclone with two single LM3886 for the main speakers, and 3x LM3886 BTL for the subwoofer.
I came over some speaker protection circuits at ebay, and wonder if this is necessary to use!

They look something like this:
Audio Speaker Protection Board DIY Components Kit for Stereo | eBay
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Old 6th November 2013, 12:32 AM   #2
DUG is offline DUG  Canada
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Read this thread:

Bought a XY LM3886 Kit.
Doug We are all learning...we can all help
"You can't stop the signal, Mal. Everything goes somewhere..."
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Old 6th November 2013, 03:12 PM   #3
Minion is offline Minion  Canada
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also you cant BTL 3 LM3886 chips , you can only bridge 2 chips ....
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Old 6th November 2013, 03:40 PM   #4
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Everything will fail eventually, doesn't matter how cheap or how good it is, it will fail.

It depends on how you think ?

Purists will argue that you don't want anything in the signal path, ie relays.

Built well, the time between failures will be high, but so will the cost of such a failure.

Even the protection circuitry can fail - there's no protection against that.
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Old 6th November 2013, 03:52 PM   #5
sesebe is offline sesebe  Romania
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If you care about your speakers, you need to protect it. The chip amplifiers are recognized to have the bad habit to be damaged by output shortcut.
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Old 6th November 2013, 04:30 PM   #6
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Yes Minion, you can bridge three LM3886 without problems. My PCB is similar to this:
Shine7 BPA300

I think I'll go for the speaker protection circuit. Actually, once, with my old TDA7294 based amp, one of the wires for the power slipped out of its socket, and made the Chip blow, and the speaker go crazy. I want to prevent that scenario form happening again.

But how does this speaker protection circuits work? Does it cut when the voltage becomes too high? Or does it break the circuit when it observes DC?
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Old 6th November 2013, 04:55 PM   #7
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The speaker protection is usually a relay in normal open, connecting the amplifier output with the speaker.
When you turn the equipment on the protection circuit will close the relay after a few seconds accounting for any start bump, and will open the relay at any time if DC normally above 2V is present at the amplifier output.
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Old 6th November 2013, 05:24 PM   #8
sreten is offline sreten  United Kingdom
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I wouldn't bother with it, more trouble that it is worth IMO.

rgds, sreten.
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Old 6th November 2013, 06:14 PM   #9
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It seems like there are two types of speaker protection kits at ebay. One is using the UPC1237, which is a dedicated speaker protection IC, and the other circuits is just using transistors and some other basic componentes.
Here are the links:
UPC1237 Speaker Protection IC Datasheet
Speaker Protection Without UPC1237
Speaker Protection With UPC1237

I've been using this forum for a while, basically just for reading. Still there are one thing at this forum that I truly don't understand; How in the world can a single forum post have 200+ pages (!!)? Many of these posts are many years old! It really makes is hard to read the whole post (If you have the same probles as the post describes) because several members "hijacks" the thread, and taking it in a new direction.
Can someone please tell me why this is done on this forum, but never on other forums?

Last edited by hansibull; 6th November 2013 at 06:19 PM. Reason: Ebay links didn't work
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Old 6th November 2013, 06:44 PM   #10
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well, a simple protection from DC is...
a capacitor.
Yess, many will consider this as something that will ruin the sonic quality of the whole thing.
mm , got news, if the cap is large enough, it won't be noticeable by any means for a human.
and will surely block any DC from the speakers.
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