"Phil Allison" wrote in message
...

"Dave Plowman (News)"
Andy

An old audio transformer I have come across is marked as "LT44" and I
that that LT44 is sometimes used to indicate a 1:1 (or 600-ohm:600-ohm)
transformer.

Not that I've heard of, but I'm from the UK.


** Maplin sell them ......



However when I measure the resistence of the tarnsformer I get 650-ohms
on the primary and 80-ohmns on the secondary which has a tap at 40-ohms.

That doesn't feel right.

DC measurements can give a guide to the turns ratio but not the
impedance.


** That is quite wrong.

With small to medium audio transformers, the rated impedance of a winding
= 10 to 20 times the DC resistance.

This fact derives directly from the *efficiency* of such transformers
being around 80% to 90 %.

The LT44 complies.




........ Phil



Maplin sell them (and the LT700 PP O/P transformer that goes with it), but I
think the actual manufacturer might possibly be Eagle Electronics.