lm3886 280watt

[croire]

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]

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]

Volumepot?

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

 

[jaudio]

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

 

[neutron7]

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]

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]

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

 

[croire]

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