I know some of you here as I have posted on the audiokarma- Grant Fidelity forum (I generated the tube rolling spreadsheet for the TubeDAC-11). Other than complimenting Project86 earlier in this thread for a fantastic review of the TD-11, I seldom post at head-fi since I have always been about my 2 channel main system. Well, that is changing dramatically in a few months as we are moving to a downtown condo in a 1927 building. Even with sound treatments in place, the main system will be reduced significantly loudness-wise.
So with that, I am ready to delve aggressively into the headphone world so I can “crank it up” when the mood strikes (which is often). I have already chosen my closed cans for this journey: the new Mr. Speakers Alpha Dogs (heavily modified Fostex T50RP’s). Rest of system is Mac Mini dedicated music server w/ J Keny USB/SPDIF converter, TubeDAC-11, “amp to be determined”, Alpha Dogs.
The Alpha Dogs have a 50 ohm impedance,. 250 mW min & 1 w/ ch or greater recommended. Sensitivity is 94 dB/ mW. With a Rat Shack SPL meter, I generally set volume to 82 dB or so w/ 85 dB peaks.
So I could use the headphone out of the TD-11 (I have some cheaper JVC HA-S400’s but wasn’t all that impressed). I assume the Tube Out probably is too much for these cans since 300 ohm or greater is mentioned by Ian in his TD-11 specs. Since these AD's are said to be harder to drive, does that allow the Tube Out to possibly be considered? Does the TD-11 back panel Y adapter to Line Out or DAC out garner any improvements vs. the front panel headphone out ? I’ll be adding a better headphone amp later on, but just curious what TD-11 owners think.
For that situation I'd definitely stick with the front panel headphone jack. I mean, you certainly could try the tube out via adapter - it's not like it costs much for the splitter. But the damping factor will be inadequate imho. Planar magnetic designs like the Alpha Dogs are less sensitive to output impedance compared to dynamic designs, but there's still a limit.