[Boatanchors] Speech Amp

[J Forster]

Power = Voltage x Current:  P = V x I

Ohm's Law:  Voltage = Current x Resistance      V = I x R, so  I = V / R

Substituting:

P = V x I  = V x ( V / R  ) or in computer V*V/R

QED.

-Jo9hn

===============

rbethman wrote:

> AFAIK,
>
> This formula won't hunt!  Please provide reference for P = V*V/R.
>
> P = E*I,   E=I*R and etc
>
> Three phase power - P =   3*(1/2)  E line * I Line * cos Theta.  [That's
> the square root of three BTW.]
> >
> > Since Power = V * V /R, if R=600 ohms and V=70 volts, there is only
> > one possible power output from the amp. (4900/600 = 8.1 W)
> >
> Bob - N0DGN
>
> J Forster wrote:
> > Take a look here:
> >
> > http://www.dvq.com/hifi/images/260a.pdf
> >
> > AFAIK, 600 ohms is used for inputs, not outputs, and is typically
> > balanced.
> >
> > A 70 V line means that the amp output is 70 V RMS at the amp's rated
> > output. The 70 V is usually stepped down at each speaker to voice coil
> > impedance. Typical transformers have taps for the desired wattage to
> > the speaker, so you can hook up a number of transformer/speaker
> > combos. So on a 10 W amp, you can hook up four 1 W and three 2 W
> > speakers. The amp looks a lot like a voltage source.
> >
> > Since Power = V * V /R, if R=600 ohms and V=70 volts, there is only
> > one possible power output from the amp. (4900/600 = 8.1 W)
> >
> > Nope, 600 ohm and 70 V are NOT the same.
> >
> > -John
> >
> > ==============
> >
> > Barrie Smith wrote:
> >
> >>   It's my impression that the 70 volt output on a PA amp is 600 ohms.
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> >
>
> --
> Bob - NØDGN