Adding headphone jack.

[Thermioniclife]

Not having the ability leave something alone, would PB, PJ and Doc object to adding a switching stereo jack to the SM2 for use with HD650's. And having said that what would be the the appropriate OPT wiring impedance for said head amp output. Thanks. Happy holidays.

[Mucker]

That is an interesting idea for certain. A common way to use a speaker amp / headphones is with a cable that has speaker taps tied to a TRS or XLR jack. Planar's like HiFiMAN HE5, HE6se, etc.. are really impressive using a speaker amplifier. HiFiMAN makes a neat external device utilizing the speaker taps to 4 pin XLR. A balanced cable for use with HD650 would be needed.

https://hifiman.com/products/detail/84

Not certain how this would work with a Stereomour II but it may be a relatively easy task to do a DIY box of similar function to optimize matching. HD650 is not very hard to drive compared to higher end planars.

I modded an old Emotiva A-100 50W speaker amp a awhile back to drive my HE6se. I used a 15/16 stepped drill bit to punch a hole into the faceplate and then used a 4 pin XLR jack wired directly to the speaker taps internally using twisted wire. Works beautifully, dead silence, and gobs of scary power. I wouldn't try doing that with a stereomour without knowing more information if it's wise to do it or not. In my case, I have Crack and SEX amps for headphones use and have plans to use Stereomour dedicated to speakers.

[Paul Birkeland]

The DC filament supply will be mandatory on the S-II to attempt to use it with headphones.  I suspect you could leave the amp set for 8 ohms for HD-650s.

[Thermioniclife]

Thanks Fellas.