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Old 12th March 2003, 11:46 PM   #1
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Default is lm3886 good for 50W sub?

Hello!!

Is it okay to use the LM3886/3875 for sub with 6ohm driver and power ability at about 50Watts??

I'm looking for some easy minimalistic and good soundin solution for that sub driver...

Thanx for any help!

Greets.
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Old 13th March 2003, 12:23 AM   #2
martioz is offline martioz  Australia
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Why not?

Have a look at this schematic:

http://home.eunet.cz/rysanek/lm3886.gif


*jak tam zima leci?*
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Old 13th March 2003, 12:35 AM   #3
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Is it specifically designed for subwoofer amplifier or for general use? I tried LM3875 with XO frequency of ~100 Hz and I had whole lotta distortion. So, I switched to OPA549 and OPA541 using the following circuit. Any comparison of these two circuits available?

http://home.attbi.com/~greggbaker/invertedLM3875.gif
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Old 13th March 2003, 01:05 AM   #4
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LM3886 would be ok but you'd want to run probably 3 in parallel or the protection circuit will start creating some very undesirable sound effects.
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Old 13th March 2003, 12:11 PM   #5
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Quote:
Originally posted by JAZZ2250
Is it specifically designed for subwoofer amplifier or for general use? I tried LM3875 with XO frequency of ~100 Hz and I had whole lotta distortion. So, I switched to OPA549 and OPA541 using the following circuit. Any comparison of these two circuits available?

http://home.attbi.com/~greggbaker/invertedLM3875.gif

Hello jazz2250 - so witch one did You use - opa549 or 541 and did You use the same values for resistors, caps etc or modified sth??

Thx for replies!!
Greets.
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Old 13th March 2003, 12:45 PM   #6
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Can you just parallell them and make sure that they have the same input signal?

-Paul
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Old 13th March 2003, 12:51 PM   #7
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Quote:
Originally posted by martioz

*jak tam zima leci?*
and how can You know polish martioz???

"a jak u was wakacje"

Pozdrawiam(Greets)
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Old 13th March 2003, 01:15 PM   #8
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Quote:
Originally posted by PaulHilgeman
Can you just parallell them and make sure that they have the same input signal?

-Paul

At the very least, you'll need to load each module's output with well matched resistors so that they share the load relatively evenly 0R1 on each output should get you somewhere in the ballpark. You'll probably also need to give each module a servo to ensure that the DC output for each module is kept close to that of the other modules so that current doesn't flow between them and cause unneccessary heat generation. All of that can be achieved with very little circuitry and can be built to have minimal impact on sound quality.
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Old 13th March 2003, 02:46 PM   #9
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Quote:
Originally posted by mad_z

Hello jazz2250 - so witch one did You use - opa549 or 541 and did You use the same values for resistors, caps etc or modified sth??
Thx for replies!!
Greets.
I tried both. Well... I'm still trying both and have not decided which one to go.
I used 22k instead of 10k in order to reduce gain. My subwoofer has 50W maximum, so I didn't want to have too much gain.
Power supply capacitors I used are 10,000 uF on each side. They are mounted on the testboard of mine, so I didn't have a chance to try capacitors of other values. Actually, I'm not sure how much capacitance I should use in the final design.
I didn't use .22 Ohm resistor at the output. I think it'll make the sound muddy. Well...it's a personal taste. You can do some experiment with that resistor.
I didn't use 1 uF capacitor across the +/- power supply rail because amplifier module was very close from the power supply capacitors. In the final design, I might need to use 0.1 uF film capacitors from each side of power supply rail to ground.
Only one bridge rectifier was used instead of two as is in the figure.
Input capacitor is currently non-polar electrolytic, but I will replace it with a film capacitor.
I hope this helps.

A picture of my crude testboard is at the following link (post #18). Don't laugh, please.
DIY subwoofer amp
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Old 14th March 2003, 12:20 AM   #10
martioz is offline martioz  Australia
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Quote:
Originally posted by mad_z


and how can You know polish martioz???

"a jak u was wakacje"

Pozdrawiam(Greets)

I moved to "Down Under" 2 years ago
Lodz is my hometown.
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