Soft Start Necessary?

dtaylo3 · 25th December 2008, 09:28 PM

I am going to build a two-channel amp with Hypex 180 modules. I have the two amp modules, the power supply and a great toroid I got from DIYCable.

How necessary and beneficial is the soft start module?

Anthony C Smith · 26th December 2008, 07:49 AM

its realy a matter of safety; using soft start allows you to scale the mains fuse correctly, instead of "chucking in a value that doesn't blow"
manufactured product in europe has to comply with EN61000-3-2 (the flicker factor) which limits inrush currents to stop lights flickering, obviously diy is exempt.
the simplest method of inrush suppression is to use an NTC thermisor in line with the torroid, or two in series if the resistance you want is not available in the current rating you need. 10R is a good starting value for the USA, limiting current to 12.5A.
watch out how you mount these though they run hot (thats how the restance drops)
this type of suppression has one drawback, line dropouts do not allow them to cool and the fuse can blow as the mains dips out for a second and comes back!

classdphile · 26th December 2008, 09:05 AM

You don't have to be concerned with line drop-outs not allowing them to cool, it is likely that they won't be hot to begin with.

25th December 2008, 09:28 PM	#1
dtaylo3 diyAudio Member Join Date: Nov 2004 Location: coloradao usa	Soft Start Necessary? I am going to build a two-channel amp with Hypex 180 modules. I have the two amp modules, the power supply and a great toroid I got from DIYCable. How necessary and beneficial is the soft start module?

26th December 2008, 07:49 AM	#2
Anthony C Smith diyAudio Member Join Date: Jun 2005 Location: Sunderland	its realy a matter of safety; using soft start allows you to scale the mains fuse correctly, instead of "chucking in a value that doesn't blow" manufactured product in europe has to comply with EN61000-3-2 (the flicker factor) which limits inrush currents to stop lights flickering, obviously diy is exempt. the simplest method of inrush suppression is to use an NTC thermisor in line with the torroid, or two in series if the resistance you want is not available in the current rating you need. 10R is a good starting value for the USA, limiting current to 12.5A. watch out how you mount these though they run hot (thats how the restance drops) this type of suppression has one drawback, line dropouts do not allow them to cool and the fuse can blow as the mains dips out for a second and comes back! __________________ Anthony C Smith MAES MinstSCE -I think rain is wet so who am I to Judge-

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26th December 2008, 09:05 AM	#3
classdphile Account Disabled Join Date: May 2008	You don't have to be concerned with line drop-outs not allowing them to cool, it is likely that they won't be hot to begin with.