I got the MassDrop 6XX for Christmas a couple of years ago and heard they were basically a 650. When a great used deal came up on the real thing, I grabbed it to do some A/B comparisons. Yep. LOL. Pretty much the same.

Bluesound Node to Topping E30 to L30ll on main setup. PC to Schiit Modi 2 to Magni 3 on secondary. HD 650 and HD 6XX, depending on what’s closest. Fiio KA5 on iOS devices with either of the above headphones or Momentum 2.0, depending on mood. I have a pair of HD 660S2 coming tomorrow. It never ends.

I’ve only had mine since June 11th, but it’s always on and I’ve had no issues. Using it with an E30 first gen. It’s sometimes in preamp mode but always part of my Bluesound Node to E30 to L30 to Pioneer SX-780 chain.

You need something that does the opposite; an adapter for your guitar to the PC. I bought this one years ago and it’s really handy- especially with good software.

https://www.amazon.com/Line-6-99-gport-GuitarPort-XT/dp/B0000AJQ42