Impedance Sansa e250.

[maxpancho]

anybody knows the impedance of Sansa e250?

[saratoga]

Back of the envelope is about 1 ohm.

Out of curiosity, what use would knowing it be?

[maxpancho]

hum, are you sure it's 1 ohm? i've read that mp3-players usually have like 16 ohm. about your question, i've heard that it's better to have your headphone's impedance close to your player's, so it would match better. so if you have headphones with impedance less then your player's, then the player is gonna be overloaded, but if you have impedance more than your player's, the volume
is less then it would be if it match perfect.

[saratoga]

hum, are you sure it's 1 ohm?

I'm getting about 1-2 ohms by computing the ratio of line out to headphone volume.  Its just a rough estimate though.

i've read that mp3-players usually have like 16 ohm. about your question, i've heard that it's better to have your headphone's impedance close to your player's, so it would match better.

Where did you hear that?

so if you have headphones with impedance less then your player's, then the player is gonna be overloaded, but if you have impedance more than your player's, the volume
is less then it would be if it match perfect.

Output impedance is generally as low as possible.  The lower it is the less power it uses and the more power the headphones receive.  The first case you mention is basically impossible to have, and the second doesn't make much sense.  The volume is always going to decrease with increasing impedance no matter the source . . .

[maxpancho]

but it's not 1 or 2, exactly http://forums.sandisk.com/sansa/board/message?board.id=e200&message.id=27720&query.id=69889#M27720
anyway i decided to buy headphones with any impednce, cause it doesnt make big sense.

[Chronon]

   I don't really see why you linked that thread.

[maxpancho]

in that topic they say it's 16ohm at least.

[soap]

in that topic they say it's 16ohm at least.

One quote is

Sansas are optimized for 16 ohm phones.

Which, itself, is a failure to understand what the math means.
The lower the impedance of the phones the more power gets transfered.
15ohm phones would get even more power.
14?  More still.

The other user, CurlySue (the one who said "it IS 16") appears to be utterly full of it, got called out on it in that thread, and ignored it.

[maxpancho]

anyway 32ohm headphones is ok?

[soap]

Way more than ok.

[maxpancho]

in this case the more the better?

[saratoga]

in this case the more the better?

Higher is easier on the amp (less distortion since its drawing less power) but quieter (again because of less power).

in that topic they say it's 16ohm at least.

That guy is clearly an idiot though.   

[maxpancho]

well, and again, what's better to have in this case? 30 or 60 ohm phones?

[soap]

Depends.  At the same sensitivity rating the 60 ohm ones will be quieter, but will they be too quiet?
But 60 ohm phones can be louder than 30 ohm phones if they are more sensitive.  Saratoga will have to answer that (how many dB is the change from 30 to 60?)

[saratoga]

well, and again, what's better to have in this case? 30 or 60 ohm phones?

Better how?  The question doesn't even make sense.

If you're not interested in understanding what impedance means, maybe you should just not worry about it . . .

But 60 ohm phones can be louder than 30 ohm phones if they are more sensitive.  Saratoga will have to answer that (how many dB is the change from 30 to 60?)

In general twice the resistance means half the power, but since you're also changing the amount of material in the headphones, the sensitivity changes too, so it could shift either way.  In general though, very high impedance headphones tend to be quieter.  The trend isn't so clear in the middle (they make incredibly loud 32 ohm IEMs for instance).