# why does impedance ratio matter?

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April 11, 2005 6:02:23 PM

Taking Jensen JT-11P-1 line input and JT-11-FLCF line output for the
sake of example: The line input tranformer has 10k:10k impedance ratio
and the line output transformer has a 600:600 ratio. The turns ratio is
1:1 on both. Why couldn't you use one in place of the other if the
turns ratio is the same?

More about : impedance ratio matter

Anonymous
April 11, 2005 10:14:28 PM

apa <tacoma57@hotmail.com> wrote:
>Taking Jensen JT-11P-1 line input and JT-11-FLCF line output for the
>sake of example: The line input tranformer has 10k:10k impedance ratio
>and the line output transformer has a 600:600 ratio. The turns ratio is
>1:1 on both. Why couldn't you use one in place of the other if the
>turns ratio is the same?

Because real world transformers aren't like the ideal ones in physics class.
Real transformers tend to ring if their load impedance isn't in a fairly
narrow range.

Generally, output transformers are designed to operate with a wider range
of load impedance than input transformers. They are also usually designed
for operation at higher levels. The downside is that they are also usually
less efficient and have higher series losses in the process.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
April 12, 2005 1:33:00 AM

It's to do with the *reflected* load on the source.
The 10k:10k i/p tranny, usually small in size, will be terminated with at
least 10k, probably higher if bridging - and the sending 600r:600r affair,
much larger, will be *looking* into about 1k down the line.
Both have to cope with full AF bandwidth. The pri/sec 1:1 idea is just to
provide DC isolation.

"apa" <tacoma57@hotmail.com> wrote in message
> Taking Jensen JT-11P-1 line input and JT-11-FLCF line output for the
> sake of example: The line input tranformer has 10k:10k impedance ratio
> and the line output transformer has a 600:600 ratio. The turns ratio is
> 1:1 on both. Why couldn't you use one in place of the other if the
> turns ratio is the same?
>
Related resources
Anonymous
April 12, 2005 5:15:01 PM

Scott Dorsey wrote:
> apa <tacoma57@hotmail.com> wrote:
> >Taking Jensen JT-11P-1 line input and JT-11-FLCF line output for the
> >sake of example: The line input tranformer has 10k:10k impedance
ratio
> >and the line output transformer has a 600:600 ratio. The turns ratio
is
> >1:1 on both. Why couldn't you use one in place of the other if the
> >turns ratio is the same?
>
> Because real world transformers aren't like the ideal ones in physics
class.
> Real transformers tend to ring if their load impedance isn't in a
fairly
> narrow range.
>
> Generally, output transformers are designed to operate with a wider
range
> of load impedance than input transformers. They are also usually
designed
> for operation at higher levels. The downside is that they are also
usually
> less efficient and have higher series losses in the process.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

I am a total ignoramous in the world of guts level electronics but
isn't a transformer with the same number of primary and secondary
windings essentially not a transformer anymore?

Mike http://www.mmeproductions.com
Anonymous
April 12, 2005 9:20:31 PM

transmogrifa <mmeprod@mmeproductions.com> wrote:
>
>I am a total ignoramous in the world of guts level electronics but
>isn't a transformer with the same number of primary and secondary
>windings essentially not a transformer anymore?

No, it's just a 1:1 transformer. It has the same input and output
impedances and voltages (well, actually it has slight loss, so the
output voltage will be a little lower than the input), but it still
is electricly isolating, which is often what you want a transformer for.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!