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serj.t.s 23rd March 2008 12:03 AM

First ever Amp buid, but cheap.
Hi :D

I decided not to go into solid state, although I have been said that
the quality obtained is much better than any chipamp.

I don't need lots of power, 15W would be more than enough, but I do wish SOME quality.

My question is if I use a low power opamp, like a LME49810(has very low THD+N), and then just design an output stage, will the result be very different than using a LM3886?

Maybe I'm missing all of the stability issues I've read about and I think are they related with the feedback loop, but in this case can't the feedback loop be purely resistive giving a constant gain?

In the end I am aiming for something like this but with a better opamp.

Will it compare?

Leolabs 24th March 2008 01:46 AM

Why not go for LM1875???

boricuaso 24th March 2008 05:53 AM

im not an electronics pro, but here is my 2 cents, if all you need is 15watts of power, you would be better off using any of all the low power chips that are out there, that only require a minimum of parts and you can use the data sheet provided by the manufacturer to build the amp.
the LME49810 is a very nice chip but i would think of it being used for higher power ratings then what you're looking for. im sure you can make it so it pushes 15watts, but with so many chips out there that are way simpler to build and are designed for that amount of power, better off with the LM3886 which is much easier to build, great sound quality, cheaper to build, low parts count and you don't even need to construct a PCB if you don't want to, and youll have power to spare.

i hope that helps
good luck

danielwritesbac 24th March 2008 10:39 AM


Originally posted by Leolabs
Why not go for LM1875???
Because a great quality little amplifier would be much too easy that way?

serj.t.s 24th March 2008 11:09 AM

LeoLabs: the LM1875 seems to me a chipamp that has a lot of distortion, assuming I can obtain an equivalente setup as that they used to measure THD, the best I can obtain is a THD of 0.03% at 20Khz and 10W, but I would probably get more. The LM3886 stays below 0.02%.

But that LME49810 or similar has a THD of 0.001%. So that's why I was wondering about using one of these and an output stage to drive the speakers. I know that this being such a trivial solution it would have been thought a long time ago, I guess I'll have to find out how to calculate the THD as the output stage will probably introduce alot.

boricuaso: I'll probably do that, since all I want is a simple solution to get some amplified sound going.

Thanks for the replies.

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