Hi guys
I’m looking at buying a UR44 but I want to know if it will drive my 300 ohm Sennheiser HD650’s.
Does anyone have the spec on its headphone amplifier ?
I would even be happy if someone could just tell me how the headphone outs drive a high impedance headphone like a HD650 etc.
They drive my AKG K601s fine (120R).
Yours should work fine, but may not be as loud as lower impedance phones. 
Thanks
In case anybody else was interested… According to Australian distributor: 35mW @ 40ohm
From Wiki:
“The impedance of headphones is of concern because of the output limitations of amplifiers. A modern pair of headphones is driven by an amplifier, with lower impedance headphones presenting a larger load. Amplifiers are not ideal; they also have some output impedance that limits the amount of power they can provide. In order to ensure an even frequency response, adequate damping factor, and undistorted sound, an amplifier should have an output impedance less than 1/8 that of the headphones it is driving (and ideally as low as possible). If output impedance is large compared to the impedance of the headphones, significantly higher distortion will be present. Therefore, lower impedance headphones will tend to be louder and more efficient, but will also demand a more capable amplifier. Higher impedance headphones will be more tolerant of amplifier limitations, but will produce less volume for a given output level.”
See also this article in SOS:
According to the schematic in the UR Manual the headphone outputs are 0.6mW @ 40ohm, however the Specification sheet states 35mW @ 40ohm 
The UR28M is also quoted as 35mw at 40ohm and was fine with my HD600s.
Did you grab the UR44 and try with ur 650’s?
Thinking about grabbing the UR22 and trying with 650’s…
THANKS!!