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Question: Impedance matching: adapter for onnecting 8 ohm headphones to modern MP3 player

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Old September 15th 06, 02:36 AM posted to rec.audio.tech
Stephan Gipp
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Posts: 15
Default Question: Impedance matching: adapter for onnecting 8 ohm headphonesto modern MP3 player

Good Music wrote:

> For Mouser's audio transformer products, they have spec sheets where they
> have the "impedance (ohms)" rated on both the primary and the secondary
> windings.
> If my headphones are 8 ohms and my MP3 player is expecting headphones in the
> 40-100 ohm range, is it as simple as buying an audio transformer with
> reasonably wide-range frequency response, and 8 ohms on one winding, and
> 40-100 ohms on the other winding?

Pretty much. In the general case you need to worry about watts also, but
in the case of headsphones .. not really. Also, getting something 'kind
of close' might be just enough. At the moment, your 8 Ohm headphone is,
say, a factor of 5-10 away from what the iPod is happy to deal with. So
of you get something 'closer' ... might just be good enough. So if you
look for a transformer that has 8 on one side and 50-200 on the other,
should work. Also, keep in mind that there is no difference between
primary and secondary in terms of what goes where.

> And once I buy two transformers (one per channel), is it as simple as (for
> each channel) connecting the 8-ohm headphone driver to the "common" and
> "hot" leads for whichever winding is rated 8 ohms, and the 1/8" headphone
> jack's "common" and "hot" leads to the other winding? Or, is there maybe
> some reason I'm supposed to connect it in the OPPOSITE way?

Per channel, just put the 8 Ohm connection on the side of the headphones
and connect the other side with the iPod.

> I'd hate to end up reducing, rather than increasing, the "apparent
> impedance" of my headphones by 5x, to appear as less than 2 ohms, and fry
> the amp on an expensive MP3 player...

That's not how it works. Worst case would be that the iPod sees the 8
Ohm (so there may be a voltag drop) and the headphone is, kind of, twice
as far away. Nothing will break, however.

BTW: did you ever connect the headphone?? What happended?

Old September 16th 06, 02:52 AM posted to rec.audio.tech
Good Music
external usenet poster
Posts: 9
Default Question: Impedance matching: adapter for onnecting 8 ohm headphones to modern MP3 player

Thanks Graham, Arny, Dave, & Stephan -

Ok! "Survey Says," connect the phones directly!

When I pick up the 1/8" L-shape replacement plug tomorrow, I'll also just
grab a couple 10-ohm resistors & see how the phones sound with & without,
and if there's no major sound difference other than slight volume drop, will
use them with (even if that means I'm "stuck on stupid" (Stephan, I
saved your info on transformers just incase.)

- Goodmusic

"Eeyore" > wrote in
message ...

> Good Music wrote:
>> >
>> > Don't even bother. Many headphones claiming to be 8 ohms aren't anyway
>> > !
>> >
>> > Just connect it and see if it sounds ok. You won't hurt anything and in
>> > any case
>> > a new pair of headphones will be the cheapest and best option if you're
>> > not happy with the results anyway.
>> >
>> > Graham

>> Thanks Graham, but I'm actually pretty intent on finding a way to
>> specifically use this specific old set of 8-ohm headphones,

> Do you know that they actually measure 8 ohms ?
>> though I don't want to "short out" my expensive MP3 player's amp.

> It's *very* unlikely that'll happen. The internal amp produces such a tiny
> amount of power that it won't be bothered.
>> The reason is these were
>> my grandad's headphones - I just like them and am set on using them,
>> whatever kind of adapter I have to make :-)

> Any adapter using a transfomer will alter the sound anyway.
> If it's really important, an external buffer amp will be best.
> Graham


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