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Old 21st April 2002, 04:15 PM   #1
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Default LM3886 Amp components

I'm building a simple LM3886 amp, pretty much like the typical application on the data sheet from national. I was wondering what ratings(power for resistors, voltage for caps) should be safe for the external components such as the resistor in parallel with the coil on the output, and the feedback components. Any info on this would be very helpful.

Thanks!!
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Old 21st April 2002, 04:35 PM   #2
Geoff is offline Geoff  United Kingdom
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http://sound.westhost.com/project19.htm

should give you all the information you need.
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Old 21st April 2002, 06:07 PM   #3
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Default Re: LM3886 Amp components

The DIY AMP Chips forum will cover off a lot of info on building your amp.

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Old 28th April 2002, 01:09 AM   #4
Ignite is offline Ignite  Canada
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Has anyone ever attempted a cheap subwoofer amp with a number of these chips used together? It seems like a pretty good idea to me.
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Old 28th April 2002, 04:11 AM   #5
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There is a national application note BPA-200 available from www.national.com that would be good for this purpose assuming that the sub doesnt dip below about 4 ohms. http://www.national.com/appinfo/audi...ation_Note.pdf
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Old 30th April 2002, 11:44 AM   #6
ssanmor is offline ssanmor  Spain
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I have recently built a subwoofer amp for my car. Apart from the switching power supply, the power stage is built from 4 LM3886's in bridge-parallel configuration.
The conecpt is similar to National's app. note, but without the servo circuits and only non-inverting amplifiers.

You only have to build 4 non-inverting stages, like the one in the data-sheet, but selecting resistor values (mainly for the ones that fix the gain) almost identical (within 1%) is critical.
Connect two stages in parallel, directly excited from the source (or better with a buffer).
You also need a inverting amplifier, made from an op-amp, to feed the other pair of stages. You have to connect the outputs together but with a 0.1Ohm/3W resistor in series.
Then connect the speaker bridged (min 4 Ohms and supply power no more than +/-27V ) You should get about 250W rms if everything goes OK.

I don't know if it is clear for you, if it is not, don't hesitate to e-mail me (ssanmor@canal21.com).

Regards
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Old 3rd May 2002, 01:33 AM   #7
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Default Sound of 3886

Hi folks,

I've been at the DIY amp chips site. There is a lot of discusions about the different sound of the 3886, the 1875 and the 3875.
Then I downloaded the PDF information from the National site, and the chips appear to be very similar, mainly the 3886 and the 3875/76.
Have any of you had a chance to listen to those differences?
I have a 3886 amp that I built for test and it sounds very nice, as long as you do not push the chip into the spike protection mode.

Also there are many discussions about an amplifier named "gaincard". What is that?

cheers

Ricren
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Old 3rd May 2002, 03:20 AM   #8
JoeBob is offline JoeBob  Canada
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The gaincard is an overpriced power-opamp amplifier based on the LM3875. It's comprised of pretty much solely of the LM3875 typical aplication.
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Old 3rd May 2002, 01:16 PM   #9
JohnG is offline JohnG  United States
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The gaincard:

http://www.sakurasystems.com/products/47amp.html

Be sure to check out the prices. Note that you need to buy the "Power Humpty" also.

Also check this out; you can perhaps guess what it might be the inside of.

http://www.interlog.com/~cfraser/int1a.jpg

http://www.interlog.com/~cfraser/int2a.jpg
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