another try on OP2343, for audio amplifier

He could be from Taiwan and not be Chinese. Tsou, for example. It's very important to keep your head when dealing with them.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Wow, please see reply below:

"Pooh Bear" ???????: snipped-for-privacy@hotmail.com...

Thanks, I got it now.

Thanks a lot! But please try to solve some more of my questions, I really appreciate.

1. OPA2343 is an OP-AMP, so it will not provide enough current to speaker.
2. How to calculate/know the minimum current requirement of a speaker?

[DSP]==>[DAC]==>[OP2343]==>AV output ==>(parallel)[LM386]==>[mini speaker]

I want to add a mini speaker output to my box, originally, I want to add mini speaker from AV output in parallel directly (I want to use a switch to control AV output or mini speaker output only, I think switch can solve the volueme affects AV output problem), but the volume is too small for mini speaker, I have tried to change gain resistor of OP2343 to a VR, I want adjust the VR to get more gain/louder, but I get the distortion.

The original gain resistor is 4.53Kohm/3.01Kohm, I change 4.53Kohm to 10Kohm VR.

Ya, but one more switch can do this, consider about cost, I will think this later.

In fact, the box will not only decode mp3, but also mpeg1,2,4 and some more ... :-) btw, do you have good chooice for mp3 only ?

Best regards, Boki.

Hi John, Sorry for past, please advice in future : )

Best regards, Boki.

"John Woodgate" ???????: snipped-for-privacy@jmwa.demon.co.uk...

What can't be done and I keep trying that? :-)

"John Woodgate" ???????: snipped-for-privacy@jmwa.demon.co.uk...

Hi, Thank you always so care about me. :p

Best regards, Boki.

"Walter Harley" ¼¶¼g©ó¶l¥ó·s»D: snipped-for-privacy@speakeasy.net...

cheer up :D

"John Woodgate" ???????:$$ snipped-for-privacy@jmwa.demon.co.uk...

I read in sci.electronics.design that Boki wrote (in ) about 'another try on OP2343, for audio amplifier', on Mon, 3 Oct 2005:

In your case, understand electronics.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Pooh Bear wrote (in ) about 'another try on OP2343, for audio amplifier', on Mon, 3 Oct 2005:

No, I didn't. What he writes doesn't look like the sort of English that other Chinese write.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Spehro Pefhany wrote (in ) about 'another try on OP2343, for audio amplifier', on Mon, 3 Oct 2005:

You do require their co-operation to ensure that. (;-)

But since I posted my article, I'm getting very short 'teaser' responses from 'boki' in colloquial English. Quite different from the fractured language of the enquiries. I'm beginning to suspect a wind-up.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

There are power opamps, such as the LM10. Whether something is an opamp has nothing to do with how much power it can supply. However, it is true that

*most* opamps are not designed to supply very much power.

The thing that defines an opamp ("operational amplifier") is that it has two high-impedance inputs, and a low-impedance output that produces a voltage that is a very very large multiple of the difference in voltage between the two inputs.

So, for instance, the LM386 is not considered an opamp (even though it is a differential voltage amplifier), because its maximum gain is only 200 or so.

Ohm's Law. Power = voltage x current, and voltage = current x resistance. So, I = sqrt(P/R). For an 8 ohm, 1W speaker, that means I = sqrt(1/8) = .35A.

It is left as a futile exercise for the reader to determine what the speaker power rating actually means, in terms of how much power can be put into the speaker in real-world situations before it is damaged. For a nominal 1W speaker, it might be anywhere from 0.1W to 10W.

Or, you could think of it in terms of speaker efficiency and desired volume. If a bare speaker (not in an enclosure) is rated at 84 dB SPL at 1m distance when driven with 1W at 1kHz (to take a reasonable example), then to achieve a volume level of 74dB, you would need 10dB less power, that is, 0.1W. I don't know how loud you're trying to get, nor how efficient a speaker you're trying to drive.

A good guideline for figuring out how much power an amplifier needs to provide, is to look at the power ratings of other amplifiers that you consider comparable.

Here is an excerpt showing some of the header fields in your post:

---------begin quoted headers--------------- Complaints-To: snipped-for-privacy@google.com Date: 2 Oct 2005 07:48:13 -0700 From: "Boki" [email address deleted] Injection-Info: g14g2000cwa.googlegroups.com; posting-host=220.135.204.7; posting-account=wDm75wwAAAAOskmtDVM1JGvNkIaEvH13 Lines: 30 Message-ID: NNTP-Posting-Date: Sun, 2 Oct 2005 14:48:18 +0000 (UTC) NNTP-Posting-Host: 220.135.204.7 Newsgroups: sci.electronics.design Organization:

Path: newssvr11.news.prodigy.com!newsdbm04.news.prodigy.com!newsdst02.news.prodigy.com!newsmst01b.news.prodigy.com!prodigy.com!newscon02.news.prodigy.com!prodigy.net!news.glorb.com!postnews.google.com!g14g2000cwa.googlegroups.com!not-for-mail Subject: another try on OP2343, for audio amplifier User-Agent: G2/0.2 X-Complaints-To: snipped-for-privacy@google.com X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12) Gecko/20050915 Firefox/1.0.7,gzip(gfe),gzip(gfe) X-Trace: posting.google.com 1128264498 24846 127.0.0.1 (2 Oct 2005

14:48:18 GMT) Xref: newsmst01b.news.prodigy.com sci.electronics.design:579532 MIME-Version: 1.0 Content-Type: text/plain; charset=big5 [snip]

----------end quoted message--------------

Note the line that says: Content-Type: text/plain; charset=big5

I'm not sure, but maybe that is what Ted Edwards was talking about?

--Mac

You don't normally see the full headers. Most newsreaders have a facility to show them though.

You can't do this with google groups AFAIK.

Graham

The LM10 is most unusual. Power op-amps are very rare. You're perfectly right of course.

However it's generally the case that power amps are specific implementations that don't make good general purpose op-amps even though they may have the usual op-amp terminals.

Too much info for Boki I suspect.

Graham

¼¶¼g©ó¶l¥ó·s»D:KfCdnQiYXa-Vj9 snipped-for-privacy@speakeasy.net...

He means both power and current.

You don't get much power without some current as well !

P = VI and all that stuff !

I think you're beginning to get it. Yes.

The output stage is capable of much more current. And hence power too.

Ok - now it's your turn to work out from P = I^2R or P = V^2/R what voltage and current is needed to drive your 8 ohm speaker with 1 W.

That'll give you an rms voltage and current.

Can you now calculate the DC supply voltage you need to be able to deliver the necessary AC voltage to the speaker ?

Graham

Thanks, I will.

"John Woodgate" ???????: snipped-for-privacy@jmwa.demon.co.uk...

If you use Outlook Express for newsgroups, you can see the headers by selecting 'properties' for the message.

Netscape that I still use for newsgroups simply has a View Headers ( all / normal / brief ) option.

Graham

I don't know why, but I use this setting long time ago... in fact, I didn't see these headers before...

BR/ Boki

"Mac" ???????: snipped-for-privacy@bar.net...

newssvr11.news.prodigy.com!newsdbm04.news.prodigy.com!newsdst02.news.prodigy.com!newsmst01b.news.prodigy.com!prodigy.com!newscon02.news.prodigy.com!prodigy.net!news.glorb.com!postnews.google.com!g14g2000cwa.googlegroups.com!not-for-mail

"Walter Harley" ¼¶¼g©ó¶l¥ó·s»D:KfCdnQiYXa-Vj9 snipped-for-privacy@speakeasy.net...

Ya, I remember this is ideal OP characteristic.

I think the 'power' here, you mean 'current', right?

Ya, 46dB is quite low, but I think the point is its output type, am I right?

Can I use this to calculate the minimum current requirement?

Good comment, thanks a lot.

Best regards, Boki.

"Pooh Bear" ???????: snipped-for-privacy@hotmail.com...

Ya, P=VI, power means V * I, power can't stand for I only, am I wrong?

I think Walter Harley has good example in previous post already.

V=sqr(P*R) V=sqr(1W*8ohm) V=2.82

Correct?

BR/ Boki.