Schiit Saga+...What’s the point of the tube?

For that tube glow. No matter the topology any amp can be made to not impart a sonic signature in other words the distortion is low enough not to color the sound.  I would guess that's the case here. 

Lots of folks here blovulating with zero understanding, kinda scary.

 I have the original Saga, the Schiit literature clearly discusses that it is a tube buffer on top of a no gain device. 
The tube thus has a variable impact, depending upon the input impedance of your amp as well as the usual other variables in any system. Used in my case with three different amps, two SS and one tube, in all cases to me it sounded fuller with better 3 dimensional shaping of instruments and the soundstage when using the tube buffer.

It is a very clean sounding device with more resolving power than my Audio Research SP6B preamp. It does not have the natural 3-D soundstage nor sound as natural and effortless as the SP6B, but I wonder whether it was fully burned in when I was comparing it. I think it has hugely improved the sound of my bedroom system (Adcom GFA535II and ATC SCM7’s). Tremendous product! 

Questions asked and answered on the manufacturer's website

But I don’t want to deal with tubes!

Then you need Saga S, the solid-state Saga. It also saves you $100.

So what’s so special about your Saga?

Lots of things. But let’s start where you probably aren’t expecting us to: in the philosophy. Yes, philosophy. Because in the past 20 years or so, audio gear has gone into full gold-plated Bentley/60’ private yacht/$120MM beach estate mode. As in, prices are completely and utterly insane. Go ahead. Look around for a remote passive preamp, and check the prices. Now add a tube stage. Oh, wait, there aren’t any of those, so check out remote controlled tube preamps.

So what’s this about it being passive or active? How does that work?

Passive preamps are great if you have short cable runs and high-impedance inputs to your power amp. On the other hand, active preamps give you the ability to run longer cables and drive low-impedance inputs on some power amps. Saga+ is both. Switch it to passive mode to bypass the tube buffer, or switch it to active mode to use the tube buffer. It’s up to you.

 And this bizarre hybrid tube buffer? What’s that?

There are plenty of tube buffers out there, but ours is unique. It’s actually a hybrid push-pull tube buffer, featuring a dual triode tube and a pair of BJTs (bipolar junction transistors), with a unique transconductance-equalizing network that pairs the tube and transistor more seamlessly, and helps cancel distortion. The result is a buffer that measures insanely well—better than some solid-state stages!

I've been enjoying audio for 50 plus years and I've auditioned ,bought and sold a lot of product.The Saga is astoundingly accomplished at its price point,particularly when engaging the tube option which is preferable in my system.

The input impedance of the amplifier to be used with the Saga is important. The output of the Saga differs between passive and buffer mode. With buffer being much lower. This as I understand it.