Re: another try on OP2343, for audio amplifier

"Boki" <bokiteam@xxxxxxxxxxxxxx> wrote in message
news:dhqrel$qi2$1@xxxxxxxxxxxxxxxxxxxx
> [...]
> 1. OPA2343 is an OP-AMP, so it will not provide enough current to speaker.

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.


> 2. How to calculate/know the minimum current requirement of a speaker?

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.





.

Relevant Pages

  • DF: why it isnt so important, but still has meaning (long!).
    ... we have an ideal voltage ... amp, it may in some cases lead to problems, of which some are outlined ... Let's assume an amplifier stage with BJTs in class AB such as we find ... Then we have the physical limitations of the power supply. ...
    (rec.audio.opinion)
  • Re: Supersizing SET
    ... elliptical loadlines may be accomodated with less distortion than with ... Negative Voltage feedback makes such an amplifier ... Except for the power level. ...
    (rec.audio.tubes)
  • Re: What a Parrot Brained Fuckwit
    ... > The amp in a condenser mic does not amplify the capsule's power level -- ... > it's a voltage amplifier. ... it can drive a low impedance load, it's useful for driving a speaker. ...
    (rec.audio.pro)
  • Re: Good capacitors
    ... The thing you were talking about was a power _cord_. ... But it's not built into an amplifier. ... I mean they make a reliable cap with good QC and I have not seen an ... cap rated for a voltage _at least_ as high as the voltage rating of ...
    (sci.electronics.design)
  • Re: audio amplifiers: +/- X VDC vs 0-X VDC
    ... Besides the obvious difference in power, how come one needs +/- power, ... or audio output amplifier, and then the "resting point" is at zero ... is really where you measure the voltage from. ... With a single supply opamp or audio amplifier, ...
    (sci.electronics.basics)