Hifiman RE-400b issue

I purchased a HM-700 with the RE-400b headphones a while back (a little before the tek video, actually) and they've been awesome headphones.  The problem is, now I can only use them with my HM-700 because they're balanced headphones, up until now I've been using the included adapter with no issues.  I lost it the other day and now I cant even find documentation as to what kind of adapter it is, I've tried googling and looking through reviews.  Anyone know if the headphones should work in stereo without an adapter?  Or does anyone know what kind of adapter that might be?  Any help would be awesome

I'm sure you can use them without it it just appears it has more of a soundstage if you use it with the player.

I did a bit of research and hifiman got back to me.  Since they're the RE-400b (the "b" is very important) they dont work with all stereo outs.  They work fine with the out on my desktop speakers, for instance (bose companion 2) but not on my phone.  The adapter needed as far as I can tell is a 3.5mm trrs female to 3.5mm trs male.  You can also contact support at hifiman and order another adapter, as I did.  I think I'll leave this here since info was really freaking hard to find, but the HM-700 does NOT come with RE-400s, its comes with a set of RE-400b, which apparently does need an adapter in certain cases.