DC-Protect Circuitry - Page 8

AndrewT · 23rd September 2006, 11:36 AM

You are a (wo)man of few words.

mikeks · 23rd September 2006, 11:45 AM

jacco vermeulen · 23rd September 2006, 12:50 PM

This reminds me of the story of the Scot who accidently wound up in the trans bar.
Please do shave your legs, Michael.

anatech · 23rd September 2006, 05:33 PM

Hi Mike,
I strongly agree with you with regard to fuses in series with the output of an amplifier.

-Chris

AKN · 23rd September 2006, 07:06 PM

Has anyone measured distorsion introduced by a fuse on output?

anatech · 23rd September 2006, 07:13 PM

Hi 4fun,
It will vary as the value and power level varies. Frequency as well I imagine (thermal time constant, not inductance).

Imagine you have a variable resistance in series with your speakers. It's constantly changing and you have no real control over it.

-Chris

AKN · 23rd September 2006, 07:25 PM

Hi anatech!

I think most crowbar output circuits will have a fuse rated much higher than normal output, fuse value just below crowbar capability. In some cases not, I have seen it many times.

I don't disagree, a fuse is not good. But I am interested how bad by measurement.

anatech · 23rd September 2006, 07:45 PM

Hi 4fun,
I'd rather see the fuses in the supply rails. The crowbar will cause those to blow. There is no reason the voltage amp section couldn't be taken off before this so there is no danger in the output going to the other rail if only one fuse blows (unlikely). Even if it tried, the crowbar short is still applied, so the other fuse blows as well.

Works for me.

Mike, you like?

-Chris

AKN · 23rd September 2006, 08:05 PM

That short silver wire inside fuse will heat up by current and change resistance. How much, anyone has graphs?

Lets not forget load eg speakers and their voice coils, plenty of wire that's heats up (and down), but that is somewhat inevitable of course.

anatech · 23rd September 2006, 08:25 PM

Hi 4fun,
That information should be available from Littlefuse or Bussman. Any other fuse manufacturer too I would think.

There might be something in here for example.

-Chris

23rd September 2006, 11:36 AM	#71
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	You are a (wo)man of few words. __________________ regards Andrew T.

23rd September 2006, 07:06 PM	#75
AKN Enjoy good sound diyAudio Member Join Date: Aug 2005 Location: In the middle of Sweden	Has anyone measured distorsion introduced by a fuse on output? __________________ / Anders

23rd September 2006, 07:25 PM	#77
AKN Enjoy good sound diyAudio Member Join Date: Aug 2005 Location: In the middle of Sweden	Hi anatech! I think most crowbar output circuits will have a fuse rated much higher than normal output, fuse value just below crowbar capability. In some cases not, I have seen it many times. I don't disagree, a fuse is not good. But I am interested how bad by measurement. __________________ / Anders

23rd September 2006, 08:05 PM	#79
AKN Enjoy good sound diyAudio Member Join Date: Aug 2005 Location: In the middle of Sweden	That short silver wire inside fuse will heat up by current and change resistance. How much, anyone has graphs? Lets not forget load eg speakers and their voice coils, plenty of wire that's heats up (and down), but that is somewhat inevitable of course. __________________ / Anders

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23rd September 2006, 11:45 AM	#72
mikeks Account Disabled Join Date: Jun 2004 Location: Animal farm

23rd September 2006, 12:50 PM	#73
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	This reminds me of the story of the Scot who accidently wound up in the trans bar. Please do shave your legs, Michael.

23rd September 2006, 05:33 PM	#74
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Mike, I strongly agree with you with regard to fuses in series with the output of an amplifier. -Chris

23rd September 2006, 07:13 PM	#76
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi 4fun, It will vary as the value and power level varies. Frequency as well I imagine (thermal time constant, not inductance). Imagine you have a variable resistance in series with your speakers. It's constantly changing and you have no real control over it. -Chris

23rd September 2006, 07:45 PM	#78
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi 4fun, I'd rather see the fuses in the supply rails. The crowbar will cause those to blow. There is no reason the voltage amp section couldn't be taken off before this so there is no danger in the output going to the other rail if only one fuse blows (unlikely). Even if it tried, the crowbar short is still applied, so the other fuse blows as well. Works for me. Mike, you like? -Chris

23rd September 2006, 08:25 PM	#80
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi 4fun, That information should be available from Littlefuse or Bussman. Any other fuse manufacturer too I would think. There might be something in here for example. -Chris

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