LM3875 comes 'back to life' after turnoff transient suppression - Page 3

Upupa Epops · 27th August 2004, 05:54 PM

Peter, it IS normal behaviour and you will observe it in case, when you have large value PS capacitors - when you use only 1 G cap, all process will be too short for " hearability ".

peranders · 27th August 2004, 05:54 PM

Pavel, the pictures show my QRP01 with LM3886 and from what I know the undervoltage protection is the same...but it may be a difference that I have a buffer....

Upupa Epops · 27th August 2004, 06:12 PM

You can make the same courses with auxiliary circuits connected on input

( with LM 3875 ).

Beggar · 27th August 2004, 06:18 PM

thanks everyone for replying

Whatever the reason for it doing this, it doesnt seem to affect the quality of the amp, so for now at least i think im going to live with it, also as i intend to use these amps with a cross over (buffer) on the same power switch it maybe that i never notice this 'problem' again. The only thing that worries me is that the cross over turn off transient may be played through the tweeters of my active system, but i guess with rail voltages of 3.5v i dont have too much to worry about

Thanks everyone... also look out for pics of my finished system which fingers crossed should be done tonight or tommorow

Beggar · 27th August 2004, 06:55 PM

Hi peter and kurt,

The caps are new (ones that came with the basic kits), so i dont think there's anything more i can do in the cap department,

I tried increasing the value of Rb to 1k22 however this made no difference, i think this is a different problem however as it occours when the supply voltages are >3v

Thanks. Nik

27th August 2004, 05:54 PM	#22
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Pavel, the pictures show my QRP01 with LM3886 and from what I know the undervoltage protection is the same...but it may be a difference that I have a buffer.... __________________ /Per-Anders (my first name) or P-A as my friends call me

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27th August 2004, 05:54 PM	#21
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Peter, it IS normal behaviour and you will observe it in case, when you have large value PS capacitors - when you use only 1 G cap, all process will be too short for " hearability ".

27th August 2004, 06:12 PM	#23
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	You can make the same courses with auxiliary circuits connected on input ( with LM 3875 ).

27th August 2004, 06:18 PM	#24
Beggar diyAudio Member Join Date: Aug 2001 Location: South East, UK	thanks everyone for replying Whatever the reason for it doing this, it doesnt seem to affect the quality of the amp, so for now at least i think im going to live with it, also as i intend to use these amps with a cross over (buffer) on the same power switch it maybe that i never notice this 'problem' again. The only thing that worries me is that the cross over turn off transient may be played through the tweeters of my active system, but i guess with rail voltages of 3.5v i dont have too much to worry about Thanks everyone... also look out for pics of my finished system which fingers crossed should be done tonight or tommorow

27th August 2004, 06:55 PM	#25
Beggar diyAudio Member Join Date: Aug 2001 Location: South East, UK	Hi peter and kurt, The caps are new (ones that came with the basic kits), so i dont think there's anything more i can do in the cap department, I tried increasing the value of Rb to 1k22 however this made no difference, i think this is a different problem however as it occours when the supply voltages are >3v Thanks. Nik

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