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Old 11th August 2009, 11:35 AM   #1
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Default Soft Start and Speaker Protection

Hi

I am considering adding the following two circuits to my 2x300VA LM3886 Chipamp


Soft Start

http://diyclub.biz/catalog/product_i...roducts_id=402


Speaker Protection

http://diyclub.biz/catalog/product_i...roducts_id=349

I am building the same amp for my father and would feel happier if I were able to lower the mains inlet fuse value.

Has any one had experience with either of these?

Thanks

Richard
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Old 11th August 2009, 12:08 PM   #2
AndrewT is offline AndrewT  Scotland
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the upc is often recommended in this Forum.
try a search for comments.
The soft start time period of 5 to 8seconds is going to seriously heat the Power Resistors.
You can either shorten the time delay to 200ms to 300ms
or
swap the Power Resistors to a Power Thermistor
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Old 11th August 2009, 12:14 PM   #3
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Maybe this? I have made this scheme for my amplifier. Power button without fixing.
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File Type: gif soft.gif (13.9 KB, 783 views)
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Old 11th August 2009, 12:15 PM   #4
Ted205 is offline Ted205  United Kingdom
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http://www.esr.co.uk/velleman/k4700.htm
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Old 11th August 2009, 12:24 PM   #5
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Quote:
Originally posted by Ted205
http://www.esr.co.uk/velleman/k4700.htm

Hi

Thanks for this link, not a bad price either. Its a shame they don't sell a soft start power module.

Richard
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Old 11th August 2009, 12:36 PM   #6
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Quote:
Originally posted by AndrewT
the upc is often recommended in this Forum.
try a search for comments.
The soft start time period of 5 to 8seconds is going to seriously heat the Power Resistors.
You can either shorten the time delay to 200ms to 300ms
or
swap the Power Resistors to a Power Thermistor

Hi Andrew

I've asked this company to provide a schematic. Why do you think they set the range between 5-8 seconds?

I'm not sure if you remember, but I purchased a couple of thermistors a while ago (see Power Supply Beginners Guide) I haven't tried these yet.

I've almost completed a pair of Bob Brines FT-1600 wide range speakers and I'd like to try and protect the new addition to the family, cant wait to fire them up!

http://www.diyaudio.com/forums/showt...30#post1891230

Thanks

Richard
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Old 11th August 2009, 12:57 PM   #7
AndrewT is offline AndrewT  Scotland
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5-8s in the mistaken belief that this is an acceptable way to slow charge the smoothing capacitors.
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Old 11th August 2009, 12:59 PM   #8
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Quote:
Originally posted by AndrewT
5-8s in the mistaken belief that this is an acceptable way to slow charge the smoothing capacitors.

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Old 11th August 2009, 06:12 PM   #9
Ted205 is offline Ted205  United Kingdom
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have you thought about making your own softstart ?

maybe a 555timer that switches a relay ?
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Old 11th August 2009, 06:18 PM   #10
PJPro is offline PJPro  England
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Take a look at these....

Loudspeaker Protection - P33.

Soft Start - P39.

I haven't actually used these myself but did order both over the weekend.
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