well i did read once that of all the products of this APPLE music gizmo .. the best sound quality is supposed to be in IPOD shuffle ..
reason being , that is gives the o/p in the square sine wave format ..
The 40Hz square wave is an extreme test, since it asks the output stage to act like an amplifier, driving to a full voltage, holding it at that level, then driving back the opposite way.
This is really a test of the output stage and possibly the power supply, but it's been noted many times that an amplifier is nothing more than a modulated power supply.
All of the digital audio players do a decent job of reproducing the square wave without a load. With the earbuds plugged in, they generally have difficulty sustaining the voltage, and it collapses back towards zero. Some sustain better than others. One in particular sustains remarkably well and subjectively has noticeably better bass response.
The reason being that the left and right channels each have two transistors, one pushing, one pulling, and no capacitor that gets discharged over time.
The ipod shuffle doesnt in theory requires a bass boost ..
even at the deepest bass frequencies the load/no load performance is very close in case of the ipod shuffle..
No matter hw mch i hated ipod shuffle .. i had to admit that this baby does pumps up the volume in the right manner ..