Low impedance headphones, in-line volume controls and bass.

[dreamlayers]

I'm still using Creative Labs EP-630 earphones with my devices. I again started using an in-line volume control with them, which adds resistance in series with the headphones. Turning down the in-line  volume control and turning up 5G iPod volume improves bass. Extremely low frequency sounds which feel more like pressure pulsations become a lot more noticeable.

This reminds me of the capacitor mod some people did with the original Archos Jukebox. This probably means the 5G iPod would benefit from a similar mod. However, components on the iPod motherboard are so tiny, and space is so tight that I don't feel like attempting the mod there.

Turning down the in-line volume control also reduces noise that can be heard during quiet parts. The 5G iPod has some constant noise and the Archos V2 Recorder has noise during hard drive spinup. The Sansa Clip Zip has the least noise, though it's not perfect. Probably the combination of the low 16 ohm impedance and high efficiency of the EP-630 earphones makes even low levels of electrical noise audible. I can tolerate all this without the volume control, but it's certainly better when reduced.

Is there any sound quality disadvantage when using an in-line volume control? Would higher impedance headphones avoid the need for adding a volume control?

[saratoga]

You're increasing the output impedance of the player via an inline resistor (assuming thats how your inline attenuator works at least), so you'll be less damped, and in theory have worse performance:

http://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html

If it actually matters to you is another matter.  I used to use an inline control on the EP-630s with the old e200v1 to reduce the background hiss and bass roll off.  This was much more noticeable to me than more theoretical concerns about damping.  The ideal solution on players like the older iPods and e200s is to use higher impedance headphones.  They had some trouble with bass roll off at 16 ohms due to the capacitors as you suspect. 

I haven't found an attenuator to be worthwhile on the Zip though.  Mine is quiet enough that even the 630s are fine.