I don't know. Maybe I should be......
Yes, it is. And it will be hard to resist.
Well, I'll just post the answer here. :)
Liquid Glass is a Single Ended amp. It only has RCA inputs on the back. The 4 pin XLR on the front is a convenience for those owners who have headphones terminated in one of these connectors. When headphones use this jack, the amp is still running single ended.
Let me know if you have more questions.