pure ipod dock

i *think* that the guys are talking about this iPod i-20 dock from PURE:
http://www.pure.com/products/product.asp?Product=VL-61429&Category=

.....The Pure has its own internal DAC, so it takes the pure digital feed from the Ipod and runs it through a better DAC. Only the pure and the Wadia do this as far as I know.

I believe that your sentence is not true - the Wadia only buffers the analog output from the iPod on its analog o/p RCA jacks. On its digital output, it is buffered digital stream. To the best of my knowledge the i170 does not have an on-board DAC.

05-18-11: Badwisdom
Can anyone explain how the pure dock allows volume control on a supposedly all digital signal ???? How is that possible ???

your mind is stuck in the analog domain method of volume control which you are trying to attach to a digital signal & are getting totally confused!! ;-)
Digital volume control has been done by Wadia since they were founded back in 1988! You do digital volume control by increasing/decreasing the bit width of the digital signal - longer bit length = higher volume, shorter bit length = lower volume. Hope that this helps.

05-19-11: Badwisdom
Bombaywalla,

i know that Accuphase and Wadia players have this kind of digital control, but whats weird on the Pure dock is that only latest iPod generation allow for that volume control, its completely disabled on ipod touch and iphone...

And unless im mistaken, other docks also disable volume control when using digital out (wadia & onkyo for ex)

OK, I see.
Nevertheless, here's the thing - once you extract the digital stream from the iPod/iPad/iPod Touch, you can play bit increase/decrease games with it on your own outside the iPod/iPad/iPod Touch environment. This is particularly true since the Pure iPod dock has its own DAC outside the iPod/iPad/iPod Touch chassis so they/Pure must be already inc/dec the bit width to suit their own DAC. At that point it becomes relatively simply to supply the user a digital volume control.
The situation is diff in the Wadia as they do have their own DAC outside the iPod/iPad/iPod Touch chassis - they merely buffer the analog output from the iPod/iPad/iPod Touch. They could have provided a digital volume control off the digital bit stream but they chose not to. Would have been really nice if they did....
In Onkyo the situation is still different - Onkyo made their iPod dock product specifically to mate to their HT receivers (I have an Onkyo iPod dock hence I did read the manual) - that's why there's only a digital out. I believe that the volume control is done thru Onkyo HT receiver's main volume control.