Soft Start and Speaker Protection

Tripmaster · 11th August 2009, 11:35 AM

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

AndrewT · 11th August 2009, 12:08 PM

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

Professor · 11th August 2009, 12:14 PM

Maybe this? I have made this scheme for my amplifier. Power button without fixing.

Ted205 · 11th August 2009, 12:15 PM

http://www.esr.co.uk/velleman/k4700.htm

Tripmaster · 11th August 2009, 12:24 PM

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

Tripmaster · 11th August 2009, 12:36 PM

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

AndrewT · 11th August 2009, 12:57 PM

5-8s in the mistaken belief that this is an acceptable way to slow charge the smoothing capacitors.

Tripmaster · 11th August 2009, 12:59 PM

Quote:

Originally posted by AndrewT
5-8s in the mistaken belief that this is an acceptable way to slow charge the smoothing capacitors.

Ted205 · 11th August 2009, 06:12 PM

have you thought about making your own softstart ?

maybe a 555timer that switches a relay ?

PJPro · 11th August 2009, 06:18 PM

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.

11th August 2009, 11:35 AM	#1
Tripmaster diyAudio Member Join Date: Feb 2008 Location: UK	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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11th August 2009, 12:08 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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

11th August 2009, 12:15 PM	#4
Ted205 diyAudio Member Join Date: Jun 2008	http://www.esr.co.uk/velleman/k4700.htm

11th August 2009, 12:57 PM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	5-8s in the mistaken belief that this is an acceptable way to slow charge the smoothing capacitors.

11th August 2009, 06:12 PM	#9
Ted205 diyAudio Member Join Date: Jun 2008	have you thought about making your own softstart ? maybe a 555timer that switches a relay ?

11th August 2009, 06:18 PM	#10
PJPro diyAudio Member Join Date: May 2009	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.