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-   -   LM3886 is good enough for PA? (http://www.diyaudio.com/forums/chip-amps/228285-lm3886-good-enough-pa.html)

samsagaz 20th January 2013 10:07 PM

LM3886 is good enough for PA?
 
Hi guys, i already build 4 amplifiers using lm3886, lm4780 and tested other ones, i really like how they sound, just want to know if will be OK to use 2 lm3886 chips in parallel to run 2x100watts stereo amps to use in PA systems?

i always used it at home for pc and for Movie theater, was thikning abt build some amps for a friends and he can use it to play music outdoor.

Maybe paralleling 2 or 3 chips to get at least 100-150w.

was thinking abt use that because are really easy to build (more than use transistors and mosfets, and maybe cheaper)

Thanks for advance.

sreten 20th January 2013 10:15 PM

Hi,

Some form of limiting / compression would probably be very useful for a PA amplifier.

rgds, sreren.

Jay 21st January 2013 12:51 AM

PA is about robustness. There are many different conditions for "PA". So we are talking about sufficient protection for the likely abuse in differing PA environments.

So the question is whether to use internal protection or additional external protection. With internal protection, I don't know about the PA environment here, but for common situations where we the owner do not have control of the amp, it is not sufficient at all.

But for "light" PA, make sure you add sufficient input capacitance, output RC and LR.

JMFahey 22nd January 2013 04:31 PM

I don't like parallelling Power Amps, at all.
Bad practice, even if suggested in the datasheet.
And "to get more power" you must go down in impedance, usually meaning speakers in parallel.
That said, I would build many individual single LM3886 50/60W PCBs, each driving its own speaker (and a couple Piezo Tweeters).
Cheap and reliable.
You may feed 2 or 3 of them from a single (properly sized) power supply, of course.
Same PSU you would have used for the doubled or tripled version, by the way.

AndrewT 23rd January 2013 09:59 AM

Quote:

Originally Posted by Jay (Post 3335259)
PA is about robustness.................

Quote:

Originally Posted by JMFahey (Post 3337590)
.......................... I would build many individual single LM3886 50/60W PCBs, each driving its own speaker (and a couple Piezo Tweeters).
Cheap and reliable.....................

I have said this many times before.

Lose one speaker or one amplifier and the show goes on.
Lose two and the show just about goes on.

But one BIG amp and a set of speakers in series/parallel and the show stops if one fails.

bear 23rd January 2013 11:59 AM

Wait.

The OP wants to "play music outdoors"?

Off a CD at a party?
Or a PA for his band?

If you want a PA for a band, what sreten said is the most important thing - make 100% certain you can not turn up the volume and *clip the amps*. Then sure, ur amp will work out fine.

Typically, 100-150watts is insufficient for a PA. Why? Because the PA has to produce undistorted (vocals) sound at a level equal or greater than that of the guitar/keyboard amps that are "X" watts, but at distortion levels of 10% or greater. The power/headroom required to do that properly is on the order of 10x the sum of all the amps on the stage. (forget about putting drums into the PA, then you need even more)

Band PA/SR really needs some extra thought and design.

samsagaz 24th January 2013 01:14 PM

thanks guys, more clear now :)


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