Today I passed by a music shop for a few things. It's a fascinating place - and not just for the guitars and the recording gear in display. I could linger there all day and not be bored for a single minute.
When I was there, a customer called in and asked the salesperson where the headphone output was located on his new electro drum kit. He had bought it a mere half hour before.
Apparently the kid was so excited when he left the shop, he wasn't able to recall anything the salesperson had told him. And at home he must have become so frustrated for not being able to hear anything at all, that he called DRUMMER-911.
Wouldn't one expect a company to make their kits as user friendly and self-explanatory as possible? My guess is that the headphone out is probably the most used feature of all in an electro drum.
Now I can't tell you exactly where it is located. But as I understood it, you'd have to perform a mini triangle pose on your knees with a slight backbend, to reach it.