[Kanashimu]

Does anyone know the output impedance of current gen/recent iPods/iTouches/iPhones?

Thanks.

 

[NA Blur]

5 Ohms
http://en.wikipedia.org/wiki/Headphone_amplifier

 

[yjt93]

Quote:

5 Ohms
http://en.wikipedia.org/wiki/Headphone_amplifier

does this mean ipod isn't a good choice for IEMs because the outpet impedance is > 1?

 

[ubercaffeinated]

Quote:

does this mean ipod isn't a good choice for IEMs because the outpet impedance is > 1?

the iphone 4 and 4s have an output impedance of less than 1 and are very good for multi BA iems.
 
4th gen ipod touches are around 7.
 
ipads are <5.
 
an output impedance of 7 is approaching iffy territory, but still probably okay according to nwavguy. going over 10 is bad according to what i've read.
 
output impedance of <1 is ideal, but <7 is probably fine. don't go over 10. definitely don't hit 18 like some of the other portable players here.
 
 

 

[NA Blur]

An output impedance of 5 ohms works well with most IEMs.  The damping factor remains pretty good for a portable device.  The Damping Factor ( DF ) = Impedance of the load / Impedance of the source.  The larger the DH the better control the amp will have over the driver.  As expected the DF depends on both the impedance of the IEM and the source in our case the 5 Ohm output impedance of the iPod.
 
DH ( iPod ) = 10 Ohms / 5 Ohms = 2
 
A poor DF would be using a 250 Ohm output impedance with a 10 Ohm load ( headphone )
DH ( poor ) = 10 / 250 = .25 ( ouch )
 
Keep in mind that the DF is just a general representation of the impedance.  There are other factors pertaining to quality here and some amps may have a high DF, but may have a large amount of negative feedback thus attenuating portions of the FR curve.  Much of the damping depends upon frequency so unless you have the DF for several frequencies with the same load the number really does not mean a lot.  Measurements of the DF can be done and can be observed typically at the fundamental which is found somewhere in the bass frequencies.  By fundamental I mean the resonance of the driver.
 
Of all of the IEM's I have tried with my iPod ( 4th Gen ) I have had little to no issues.

 

[elfary]

Quote:

An output impedance of 5 ohms works well with most IEMs.  The damping factor remains pretty good for a portable device.  The Damping Factor ( DF ) = Impedance of the load / Impedance of the source.  The larger the DH the better control the amp will have over the driver.  As expected the DF depends on both the impedance of the IEM and the source in our case the 5 Ohm output impedance of the iPod.
 
DH ( iPod ) = 10 Ohms / 5 Ohms = 2
 
A poor DF would be using a 250 Ohm output impedance with a 10 Ohm load ( headphone )
DH ( poor ) = 10 / 250 = .25 ( ouch )
 
Keep in mind that the DF is just a general representation of the impedance.  There are other factors pertaining to quality here and some amps may have a high DF, but may have a large amount of negative feedback thus attenuating portions of the FR curve.  Much of the damping depends upon frequency so unless you have the DF for several frequencies with the same load the number really does not mean a lot.  Measurements of the DF can be done and can be observed typically at the fundamental which is found somewhere in the bass frequencies.  By fundamental I mean the resonance of the driver.
 
Of all of the IEM's I have tried with my iPod ( 4th Gen ) I have had little to no issues.

 
I'm doing some math of an iPod Classic driving a Shure SE420 and a Westone UM3x.
 
The frequency response deviation that i find is 1.03 dB when feeding the SE420 and 1.32dB when feeding the UM3x. This in the 0-10kHz region.
 
The UM3x minimum impedance at DC is 27 Ohms and maximum is 110 Ohms at the 1k area.
 
The SE420 minumum impedance is 20 Ohms at DC and 45 at 10kHz.3
 
Subjectively, the difference between using the iBasso T3 to achieve perfect linearity or just the headphone out is slight in both cases though more audible on the SE420 (I guess that its flatness is the cause even if the figure is lower than for the UM3x).
 
I can't notice any difference as for the damping goes. Thightness of bass is the same to my ears whether i amp the Classic or whether i use the headphone out.
 
I can recall when i did this test driving a Shure SE530 the 5Ohms of output impedance of the Classic hpo posed more of a problem since i could notice clearly how the treble was better when amped with the T3 than when amped thru the Classic headphone out. I suppose the reason was the 7 ohms of minimum impedance that the 530 has at 5kHz which lead to a hole at this region when not using a low z headphone amp.