lm3886 280watt

croire · 27th May 2005, 01:46 PM

i want to build a 280watt with 8 lm3886 ;/channel to make a home cinema

what do you think about this

R7 are 0.22 ohm
+u and -u are +- 40volt
what can i change in the diagram to improve the ampli

cordially

jaudio · 27th May 2005, 08:36 PM

What is the purpose of P1?. I think part of figure 12 is missing,if not, both side s1 and s2 should match( r4,r5 and c1).

tobias_svensk · 27th May 2005, 09:00 PM

Volumepot?

I think they have just skipped the feedback part because the schematic would be "blurry" ?

jaudio · 27th May 2005, 09:09 PM

If dephaseur is a chip(ie. drv134)that will split the signal,why would two pots be needed. they might add balancing problems.

neutron7 · 28th May 2005, 04:22 AM

from what i understand, parallel amps need to be closely matched as possible. so they are not driving into each others outputs and causing heat and distortion..

each of the 8 amplifiers has 3 capacitors (1 electrolytic even) and 4 resistors affecting the feedback loop.any variation will cause difference in the outputs and distortion.

try and match them as well as you can.

I also wonder what may happen if spike protection was to kick in at different times on the different chips.

Greg Erskine · 28th May 2005, 04:31 AM

I was wondering why you would need to repeat the zobel network R3/C3 for each chip.

Also, isn't bridging into 4 ohms a problem.

Circlotron · 28th May 2005, 05:41 AM

Maybe so you can have each zobel right at the pins of each chip for best effect at HF.

croire · 28th May 2005, 02:48 PM

the diagram of the balanced preamp

so i won t use this preamp , i will use the dvr134 or other

in the diagram of the ampli lm3886 i use 1% resistors, silvermica 1% for the10pf=c1, c3=MKP 1%, and C5 C6=1000µf
we can use c1 10pf to 40 pf what is the best for c1

cordially

27th May 2005, 01:46 PM	#1
croire diyAudio Member Join Date: Dec 2003 Location: rouen	lm3886 280watt i want to build a 280watt with 8 lm3886 ;/channel to make a home cinema what do you think about this R7 are 0.22 ohm +u and -u are +- 40volt what can i change in the diagram to improve the ampli cordially

28th May 2005, 04:31 AM	#6
Greg Erskine diyAudio Member Join Date: Jan 2002 Location: Sydney/Australia	I was wondering why you would need to repeat the zobel network R3/C3 for each chip. Also, isn't bridging into 4 ohms a problem. __________________ Greg Erskine

28th May 2005, 05:41 AM	#7
Circlotron diyAudio Member Join Date: Jun 2002 Location: Melbourne, Australia	Maybe so you can have each zobel right at the pins of each chip for best effect at HF. __________________ Best-ever T/S parameter spreadsheet. http://www.diyaudio.com/forums/multi...tml#post353269

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27th May 2005, 08:36 PM	#2
jaudio diyAudio Member Join Date: Oct 2004	What is the purpose of P1?. I think part of figure 12 is missing,if not, both side s1 and s2 should match( r4,r5 and c1).

27th May 2005, 09:00 PM	#3
tobias_svensk diyAudio Member Join Date: Jan 2004 Location: Hudiksvall	Volumepot? I think they have just skipped the feedback part because the schematic would be "blurry" ?

27th May 2005, 09:09 PM	#4
jaudio diyAudio Member Join Date: Oct 2004	If dephaseur is a chip(ie. drv134)that will split the signal,why would two pots be needed. they might add balancing problems.

28th May 2005, 04:22 AM	#5
neutron7 diyAudio Member Join Date: Dec 2003 Location: Toronto Canada	from what i understand, parallel amps need to be closely matched as possible. so they are not driving into each others outputs and causing heat and distortion.. each of the 8 amplifiers has 3 capacitors (1 electrolytic even) and 4 resistors affecting the feedback loop.any variation will cause difference in the outputs and distortion. try and match them as well as you can. I also wonder what may happen if spike protection was to kick in at different times on the different chips.

28th May 2005, 02:48 PM	#8
croire diyAudio Member Join Date: Dec 2003 Location: rouen	the diagram of the balanced preamp so i won t use this preamp , i will use the dvr134 or other in the diagram of the ampli lm3886 i use 1% resistors, silvermica 1% for the10pf=c1, c3=MKP 1%, and C5 C6=1000µf we can use c1 10pf to 40 pf what is the best for c1 cordially

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