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Chip Amps Amplifiers based on integrated circuits

Increasing MyRef speaker protection circuit sensitivity
Increasing MyRef speaker protection circuit sensitivity
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Old 22nd June 2012, 10:51 AM   #1
paskal9 is offline paskal9  Malaysia
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Default Increasing MyRef speaker protection circuit sensitivity

since i've blown two of my bridged modules because of accidental shorting of the tab to casing (which in turn burned my speakers connected to it), i'm considering of rebuilding the other modules with speaker protection similar to the one used in myref into it.

anybody could advice me on how to increase the sensitivity of the protection circuit like the one below?
Click the image to open in full size.
this is part of the miniref schematic, which is similar to the one used in my ref.

with the current component value, it triggers at about 4v something. could it be made to trigger at say around 1v? any advice/suggestion/criticism would be much appreciated.
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Old 22nd June 2012, 02:57 PM   #2
AndrewT is online now AndrewT  Scotland
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the circuit around Q3 must be replaced.

Better to start with a proper protection/delay circuit rather than this VERY basic version compromised by trying too hard to minimise the number of components.
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Old 22nd June 2012, 03:50 PM   #3
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by AndrewT View Post
the circuit around Q3 must be replaced.

Better to start with a proper protection/delay circuit rather than this VERY basic version compromised by trying too hard to minimise the number of components.
thanks for the reply andrew. well frankly i would, if i could. but i couldn't. space is a luxury that i don't have. a very basic protection is still better than no protection. lesson learned. a pricey one at that.

Click the image to open in full size.
the original modules have a size of 5cm x 9cm. i managed to squeeze the protection circuit inside while increasing the width another 1 cm to 5cm x 10cm

Click the image to open in full size.
as the original amp are arranged to accommodate amp modules with the original size of 5x9, large amount of size increase would mean that i have to retrofit most of the boards back.
as you can see, it's already packed as it is. my options are currently limited to the simple protection circuit.
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Old 30th November 2017, 03:51 AM   #4
varun21 is offline varun21
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Quote:
Originally Posted by AndrewT View Post
the circuit around Q3 must be replaced.

Better to start with a proper protection/delay circuit rather than this VERY basic version compromised by trying too hard to minimise the number of components.
Sorry to bump an old thread. Any schematic / parts suggestions?
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Old 30th November 2017, 08:03 AM   #5
Mark Whitney is offline Mark Whitney  Netherlands
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The uPC1237 is often used. Use one per channel if you are building mono.
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Old 30th November 2017, 09:13 AM   #6
varun21 is offline varun21
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Sorry, I meant how to improve the circuit around Q3. The ic based option is a different beast altogether.
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Old 30th November 2017, 10:08 AM   #7
Mark Whitney is offline Mark Whitney  Netherlands
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I think the point AndrewT is making is that a new design would be better than trying to fix the existing one.
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Old 30th November 2017, 03:38 PM   #8
Joseph K is offline Joseph K  Hungary
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To the contrary of Andrew's affermation, that very basic and simple protection built into the original Myref design -- works like a charm, always.
Why should one change a working design?

Last edited by Joseph K; 30th November 2017 at 03:44 PM.
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Old 30th November 2017, 04:34 PM   #9
varun21 is offline varun21
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Because mine didn't kick in and I was measuring about 6Vdc on the speaker terminals.

I have C546B (Q1, Q3) and C63916 (Q2) as per the schematic. There are two things I want to fix.

1. Delay the start to about 2 seconds.
2. Make sure that it kicks in at an unsafe offset.
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Old 30th November 2017, 05:26 PM   #10
Joseph K is offline Joseph K  Hungary
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Replace the 10k with 22k, for a lower treshold..
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