speaker protection and output short

patriz · 10th January 2005, 11:26 AM

I pick up in some post to use the speaker protection with the realy not in series with the signal but shunt to ground so if I have some dc the realy swicth the output to to ground but this mean output short . Lm3875 datasheet speak of in chip short output protection , this mean I can use this idea with no problem?
Gio

Nuuk · 10th January 2005, 12:40 PM

When shunting the input of the LM3875 to ground, you need normally closed relays whereas the relays used for the speaker protection modules are the normally open type.

But yes, it is OK to shunt the input of the LM3875 to ground while the amp powers up.

patriz · 10th January 2005, 02:06 PM

actually my idea was to shunt the 3875 output to ground in order to avoid dc in the speaker. The problem could be, in a protection project like the Velleman kt4700 with the soft start , all the time before the relays activation the output is shorted to ground

Nuuk · 10th January 2005, 03:55 PM

Quote:

The problem could be, in a protection project like the Velleman kt4700 with the soft start , all the time before the relays activation the output is shorted to ground

AFAIK, all the Velleman 4700 does is disconnect the speakers from the amp for a short while before the amp is fully powered up.

10th January 2005, 11:26 AM	#1
patriz diyAudio Member Join Date: Oct 2004	speaker protection and output short I pick up in some post to use the speaker protection with the realy not in series with the signal but shunt to ground so if I have some dc the realy swicth the output to to ground but this mean output short . Lm3875 datasheet speak of in chip short output protection , this mean I can use this idea with no problem? Gio

10th January 2005, 12:40 PM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	When shunting the input of the LM3875 to ground, you need normally closed relays whereas the relays used for the speaker protection modules are the normally open type. But yes, it is OK to shunt the input of the LM3875 to ground while the amp powers up. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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10th January 2005, 02:06 PM	#3
patriz diyAudio Member Join Date: Oct 2004	actually my idea was to shunt the 3875 output to ground in order to avoid dc in the speaker. The problem could be, in a protection project like the Velleman kt4700 with the soft start , all the time before the relays activation the output is shorted to ground

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