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Old 24th November 2007, 02:58 PM   #1
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Default Chip Amps with no DC PROTECTION fine?

i observed that no one includes dc protection for their chip amps, be it diy or commercial ones. is it because no one bothers? or are these chips so reliable that no one should worry?
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Old 24th November 2007, 03:07 PM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
a chipamp is an opamp with a high current output stage that can take ~+-40Vdc on it's supply rails.

As such it is a DC amplifier and can and will output DC, if DC is presented to it's input.

If one chooses a topology and/or protection scheme that allows DC to pass through the amplifier then face the consequences, eventually.

Most builders are looking for a low component count, easy to reproduce amplifier. They generally choose chipamps because they see easy buildability without regard to making any design decisions, for good or bad.
It is not reliability or lack of it in the chipamp that is the problem. It is a designer decision.
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Old 24th November 2007, 03:08 PM   #3
Nuuk is offline Nuuk  United Kingdom
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It's a personal choice really! There have been tales of disaster on this forum but generally, they chips, when properly implemented are as safe as any other type of amplifier.

If you are worried, use one of the speaker protection modules that you can usually buy as kits like this one from Quasar.
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Old 26th November 2007, 04:27 PM   #4
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Would this speaker protection circuit be needed when using a TA2024's "intelligent circuit protection" feature or is that enough?
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Old 27th November 2007, 03:36 AM   #5
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Quote:
Originally posted by Nuuk
It's a personal choice really! There have been tales of disaster on this forum but generally, they chips, when properly implemented are as safe as any other type of amplifier.

If you are worried, use one of the speaker protection modules that you can usually buy as kits like this one from Quasar.
i have made a diligent search thru this forum and it seems like the cause of such disasters had been due to carelessness.
my actual concern has been on the reliability issues ie. does it known to fail over time, or any other parts of the implementation that fails eg. one half of the PSU failures that may cause the output of the damaging DC.
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Old 27th November 2007, 04:26 AM   #6
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Quote:
Originally posted by commstech
my actual concern has been on the reliability issues ie. does it known to fail over time, or any other parts of the implementation that fails eg. one half of the PSU failures that may cause the output of the damaging DC.
Failure of one rail (half of the PS) will not produce DC at the output. The chip is also protected against output being shorted.
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Old 27th November 2007, 05:57 AM   #7
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Quote:
Originally posted by Peter Daniel


Failure of one rail (half of the PS) will not produce DC at the output. The chip is also protected against output being shorted.

PD, thanks! that has put my worry to rest.
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Old 27th November 2007, 08:15 AM   #8
Nuuk is offline Nuuk  United Kingdom
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Quote:
my actual concern has been on the reliability issues ie. does it known to fail over time, or any other parts of the implementation that fails eg. one half of the PSU failures that may cause the output of the damaging DC.
And I can add that I have never had any speaker damage from a chip failure using the LM3875, LM3886, or OPA541 chips. So yes, rest assured, if you implement a chip amp properly, you shouldn't have any problems.

I think speaker protection is useful though when you are doing a lot of experimentation where you could make a simple mistake, or you are trying something 'new' and untried! Having said that, I now tend to run anything 'new' on old speakers for a few days rather than risk my better speakers!
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Old 27th November 2007, 09:01 AM   #9
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Quote:
Originally posted by Nuuk


And I can add that I have never had any speaker damage from a chip failure using the LM3875, LM3886, or OPA541 chips. So yes, rest assured, if you implement a chip amp properly, you shouldn't have any problems.

I think speaker protection is useful though when you are doing a lot of experimentation where you could make a simple mistake, or you are trying something 'new' and untried! Having said that, I now tend to run anything 'new' on old speakers for a few days rather than risk my better speakers!
This is certainly very good assurance for me. thanks.
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Old 27th November 2007, 02:24 PM   #10
fdeck is offline fdeck  United States
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I wonder if a possible compromise is to run amplifiers under test, through some big electrolytics wired back to back.

As for DC protection, I think the answer has to be: How safe do you want to make it? My understanding is that DC protection guards against failures such as an output transistor turning into a short circuit. I would be interested in knowing if the audio power amp chips are either: a) Sufficiently reliable; or, b) internally protected, to the point where external protection is unnecessary. The chip amps do have the advantage of instantaneous temperature monitoring of the output devices.

Thoughts?
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