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Old 17th April 2017, 03:49 AM   #21
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Yes it is versatile for cheap equipment.

I haven't looked into car radio chips too much. I haven't been motivated. But I would be surprised if any of the amplifier chips were rated less than 18 volts max Vcc. And with modern "rail to rail" technology, I'm sure there's better car radio chips.

I agree that it would make a good boombox amplifier. You could biamp, or drive two woofers with ease.

I've read that DIYers have obtained good results with this chip. I've been tempted to check it out but I have more interesting projects. You could go real cheap by running it off of a large laptop supply. For that matter, you could do the same thing with an LM1875 single ended circuit.

So what do you think of my LM3886 bridge amp idea using the DRV134? The chip uses laser adjusted resistors for precision. Seems to me it does a lot of heavy lifting for the money. I haven't worked out the details but it seems doable to me.
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Old 17th April 2017, 12:37 PM   #22
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not a bad idea, however i think the concept lacks the ability to "heal" the shortcommings of lm3886 or.. any other amplifier.

i think if i wanted to do something to get a better result i would take an opamp, and have the poweramplifier in its feedback loop. thatway the opamp will do whatever it can to correct the poweramplifier, yielding something close to the opamp driving a light load.
or probably just build a push-pull output stage and incorporate that into the feedback loop.
supposedly a fast opamp can steer things to the right direction without problems.
finding opamps that have reasonable output swing is the bigger problem btw.
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Old 17th April 2017, 03:18 PM   #23
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Yeah, I've experimented with a couple of nested feedback topologies and built a headphone amplifier using nested feedback. I realize that an op amp on the front end can straighten things out. You have to decouple the feedback loop in the middle to make something like a 3886 nested circuit; it's way slower than any op amp you would put in the front end. I know there's other ways to avoid gain bandwidth product associated phase shift problems.

I think one of the "shortcomings" of the 3886 is limited power/voltage swing into an 8 ohm load. Bridge amp will address this. I'm using the power amp in an old Pioneer receiver right now (wired around everything else). It's rated 35 watts/ channel into 8 ohms continuous (and does it too because I measured) but easily achieves 100 watt peaks without clipping. This is actually very practical for music reproduction. But why did Pioneer design it that way? Because it's designed to drive two 8 ohm speakers in series. It has a pretty high voltage power supply (+/- 50 volts if I remember correctly) so it gets hot but delivers the goods without clipping if you don't drive it too hard.

I might give it a whirl unless I get distracted by a "better" idea.
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Old 17th April 2017, 03:40 PM   #24
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lm3886 is not quite the best chip to bridge or parallel in my opinion.
tda 7293 and 94 offer pretty fantastic features to amke them bridged, paralleld, or parallel and bridge 4 modules, or even more. you can build a bridged setup and parallel 3 of those if you wish so. witch is stupid amount of current capacity, and a verry hefty voltage swing.
but if you need that kind of power class D is a better friend.
a pair of decent speakers in a living room rarely needs more than 10 watts / channel. even if you want your ears to bleed.
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Old 18th April 2017, 03:52 PM   #25
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I know about the TDA chips. I have a couple of boards using the TDA chips that I pulled out of boomboxes and "tabletop hi-fis." When you wire line level output of a hi-fi preamp directly to the input of these amps, they all provide surprisingly good performance. And after seeing these "budget" commercial applications I realize that they're pretty versatile.

I know their advantages too: higher Vcc, no thermal runaway, super easy to parallel. While popular gainclones usually use the 3886, commercial designs usually use a TDAxxx chip.

Is there really a disadvantage to using the TDA chips in a"hi-fi" circuit, over a 3886?
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Old 18th April 2017, 06:17 PM   #26
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none i know of. i found tda to be a better choice overall..
specially if you plan to paralell them, or bridge them.
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Old 19th April 2017, 06:27 AM   #27
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Thanks.

I'll have to have another look at the datasheet.
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