Mofi is correct, as usual, certainly with respect to the 105 having a reasonably hefty built-in headphone amplifier. (I have no knowledge of its sonics, but based in part on his comments I'd expect it to be pretty good in that respect also).
As indicated on page 85 (pdf page 89) of the manual, the 105's headphone output can provide 63 mW (milliwatts) into the 150 ohm impedance of the HD700, which is way more than enough for anyone who isn't interested in having their hearing damaged. (Based on the 105 db/1 volt sensitivity and 150 ohm impedance of those phones, it can be calculated that 63 mW will drive them to an SPL of about 115 db).
There's no spec for the 105 corresponding to the 22 ohm impedance of the B&W P7, but the 105's output rating of 187 mW for a 32 ohm load would seem to indicate no problem at all in that case either (although I'd be hesitant to choose phones having significantly lower impedances than 22 ohms, given the lack of ratings into low impedances).
So the answer to "will I need to buy a headphone amplifier?" is no. Although it is not inconceivable that you might eventually PREFER to buy a headphone amplifier.
Regards,
-- Al
As indicated on page 85 (pdf page 89) of the manual, the 105's headphone output can provide 63 mW (milliwatts) into the 150 ohm impedance of the HD700, which is way more than enough for anyone who isn't interested in having their hearing damaged. (Based on the 105 db/1 volt sensitivity and 150 ohm impedance of those phones, it can be calculated that 63 mW will drive them to an SPL of about 115 db).
There's no spec for the 105 corresponding to the 22 ohm impedance of the B&W P7, but the 105's output rating of 187 mW for a 32 ohm load would seem to indicate no problem at all in that case either (although I'd be hesitant to choose phones having significantly lower impedances than 22 ohms, given the lack of ratings into low impedances).
So the answer to "will I need to buy a headphone amplifier?" is no. Although it is not inconceivable that you might eventually PREFER to buy a headphone amplifier.
Regards,
-- Al