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Old 27th May 2016, 03:40 PM   #1
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Default LM3886 speaker protection from Ebay?

I ordered all the parts to build my LM3886 amplifier but as I am waiting for the parts I stumbled onto the various DC speaker protection boards that one can find on ebay.

examples are
AC 12 16V Audio Amplifier Speaker Protection Board DIY Components Kit for Stereo | eBay
15A Current relay Speaker protection board Kit for DIY
UPC1237 Dual Channel Speaker Protection Circuit Board DC 12V 24V Boot Mute Delay | eBay
Dual 2 Channel UPC1237 Speaker Protection Board DIY Kit Boot Delay DC Protection | eBay
UPC1237 Speaker Protection Board Compatible with The BTL Protection | eBay

Did anyone try these protection circuits? And is it recommended to use them or do these cheap kits pose a greater risk than a (real) LM3886 on its own?

honorable mention which even includes an RL circuit:
1pair Mono UPC1237 Speaker Protection Board DIY Kits Mirror Symmetry Circuit | eBay
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Old 27th May 2016, 04:05 PM   #2
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Hi, those links do not work.

The only speaker protection you need is protection against DC on the output. This can happen if you fuse both DC rails and one fuse blows due to over current or a faulty chip or an assembling error. First, don't fuse it that way but use a proper fuse at the primary side of the power transformer. I did use loads of LM3886's for over 20 years now but never encountered a faulty or broken chip.

IMHO a separate DC protection is only good for your peace of mind.
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Old 27th May 2016, 04:10 PM   #3
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I wasn't planning on fusing the rails for that exact reason, merely a 1 or maybe 1.5 A slow blow fuse on the primary side. but judging from what you say it sounds like the LM3886 is safe enough to run without dc protection

For me the links work by the way?
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Old 28th May 2016, 09:25 AM   #4
AndrewT is offline AndrewT  Scotland
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The 3886 sends out DC when in fault condition, or it loses one supply rail.
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Old 28th May 2016, 11:59 PM   #5
Hogwild is offline Hogwild  Canada
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Gideon1990:

I just finished assembling four of these a couple of weeks ago.

Soft starting switch full kit for power amplifier !
from eBay seller "jims_audio"
Soft Starting Switch Full KIT FOR Power Amplifier | eBay

I haven't tested them yet, but I'll probably be doing so in the next couple of weeks. If you like, I can share whatever findings I have.
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Old 29th May 2016, 12:42 AM   #6
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I have started adding DC protection to all my amplifiers.
It doesn't take too many components to do it.
I use an 8 pin PIC to monitor audio out and control a speaker relay.
The software is minimal.

DC protection wont save speakers from simple over driving but they will help if an output transistor fails.
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Old 29th May 2016, 10:49 PM   #7
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@hogwild

Sure let me and everybody know about your findings. For a lot of amp kits there seems to be a lot of info on which kits are alright and which sucks so more info is welcome.


@nigelwright7557

Is the information about your solution available somewhere?
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Old 30th May 2016, 12:40 AM   #8
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Quote:
Originally Posted by gideon1990 View Post
@hogwild


@nigelwright7557

Is the information about your solution available somewhere?
Its a home build I used. It involves programming a PIC.

I believe there is an IC that can do the job but I cant remember its number.
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Old 30th May 2016, 08:42 AM   #9
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Quote:
Originally Posted by nigelwright7557 View Post
Its a home build I used. It involves programming a PIC.

I believe there is an IC that can do the job but I cant remember its number.
UCP1237

Its what most of those Ebay kits are based off
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Old 30th May 2016, 10:45 AM   #10
AndrewT is offline AndrewT  Scotland
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There are many mentions of that UCP1237 on this Forum.
Search for some implementations. You should find at least one you like.
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