[Phishin Phool]

I recently invested in my first tube amp and it has jumpers to select between either 10 or 68 ohm resistances on the output. I am not sure I understand which I should use. I have several sets of headphones of 32, 45, and 250 ohm resistances (M50's, se-a1000, dt990). I don't really notice a difference on either setting with my dt990's (250 Ohm resistance) which have been most of my listening but I have done a lttle with my se-a1000,s (45 Ohm resistance). I want to use whatever setting is most appropriate and certainly don't want to damage any cans I use. Many thanks-jk

 

[NA Blur]

Use the low setting.  You can read about audio damping factor which will help you understand a bit more about why the output impedance is important.

 

[PurpleAngel]

I recently invested in my first tube amp and it has jumpers to select between either 10 or 68 ohm resistances on the output. I am not sure I understand which I should use. I have several sets of headphones of 32, 45, and 250 ohm resistances (M50's, se-a1000, dt990). I don't really notice a difference on either setting with my dt990's (250 Ohm resistance) which have been most of my listening but I have done a lttle with my se-a1000,s (45 Ohm resistance). I want to use whatever setting is most appropriate and certainly don't want to damage any cans I use. Many thanks-jk

Usually it's preferred to have the headphone impedance (Ohms) to be 8 to 10 times the impedance of whatever source the headphones are plugged into, but i guess what really matters is what sounds best to you.
So with 45-Ohm headphones, you want the impedance of the amplifier to be 4.5-Ohms or less, so for the SE-A1000, the10-Ohm setting on the amp should be better then the 68-Ohm setting.

 

[Phishin Phool]

Thanks !