Re: What a Parrot Brained Fuckwit

Phil Allison <philallison@xxxxxxxxxx> wrote:

> "Adrian Tuddenham"
> >
> >> Are there any amplitude quantities, for which dB is used to
> >> compare them, which are not proportional to power when
> >> squared?
> >
> > Yes. Comparing voltage levels at points of different impedance.
> >
>
>
> ** Not true.
>
> If two points are involved, then you have a *voltage gain* (or loss)
> between the two quoted in dB.
>
> A power amp with 29 dB voltage gain will deliver twice the power into a load
> compared to one with 26 dB voltage gain under the same conditions.
>
> So the dB figure still relates to relative power .

You have fallen into a trap:

The two voltage levels you have just compared *were* at the same
impedance because they were measured at the same place, the output.

Compare voltages at two different impedance points (e.g. the output and
the input) and you will not get the power equalling the square of the
voltage ratio unless those two impedances happen to be the same.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
.

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