[Boatanchors] Speech Amp

[J Forster]

Transformer ratings are more derived from the voltage and current ratings of the
wires and turns ratio, not the impedance of their magnetizing inductance. If you were
to measure the impedance of say a  400 ohm to 4 ohm transistor output transformer
over 40 to 5000 Hz, with the secondary open circuited, you would not get anything
like 400 ohms. You would be measuring the parallel combination of the magnetizing
inductance and core loss, reflected as a resistance; in series with the leakage
inductance and primary DC resistance.

Audio transformer are marked with frequency limits for the following reason:

Low frequency limit is set by saturation of the core material at the max specified
input voltage
High frequency limit is set by acceptable eddy current (core) losse at the max
specified input voltage.

-John

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

rbethman wrote:

> And which transformers have you seen with the impedance marked on them
> WITHOUT the frequency specified? It doesn't matter if they are audio OR
> power.
>
> A short circuit analysis to determine relay settings and fuse sizes
> requires BOTH.
>
> I sure hope you don't teach!
>
> Bob - N0DGN
>
> J Forster wrote:
> > rbethman wrote:
> >
> >
> >> V represents Voltage in terms of DC.  Even as far back in engineering
> >> tomes dated 1962.
> >>
> >> AC voltages, even audio, has been represented as E.
> >>
> >
> > V and E are interchangeable.
> >
> >
> >> Impedance also requires FREQUENCY.
> >>
> >
> > Really? How about a 100 Ohm, non-inductive resistor.
> >
> > In general, an impedance has a real and a reactive part, of the form (A+jB). If
> > the reactive part is zero, it's still an impedance, but it is not frequency
> > dependent.
> >
> > -John
> >
> > ===============
> >
> > _______________________________________________
> >
> >
>
> --
> Bob - N?DGN