Hello Everyone,
 
I was hoping someone with fresh ears could help me out.   It seems to me that once I introduced a tube pre-amp into my vocal chain, my "S" sounds seemed to have gotten a little less bright/sharp.
 
I have an AKG C214 mic, Steinberg UR22 audio interface and a Presonus TubPre V2.
 
I recorded 2 vocal takes here seperated by a short piano note.  The first one is the mic right into the audio interface followed by a piano note, then followed by a vocal take going into the tube preamp and then the audio interface.
 
I think the 2nd take isn't as bright on the "S" sounds.  Can anyone help confirm?  If so, I think i might ditch the pre-amp all together as the tonality seems almost the same between the two.
 
https://www.dropbox.com/s...7ldelsz7/test.wav?dl=0
 
 
Thanks for helping me out here.
 
Adam

That tube pre is like the Presonus BlueTube preamp I had (I had as it is gone).  The tube in it is not a true high voltage tube amplifier but the typical "starved plate" design and basically nothing more than a buffer stage.  I experimented with different 12AX7 tubes in the one I had, some were better than others, including the original factory tube. 

so, is this typical tube behaviour?  Muffling up the "S" sound?

I haven't heard your examples, but if you feel the tube is affecting your sound for the worse - and especially if otherwise you hear little difference between the two - then yes, skip the tube-pre.  Being a "budget" unit, I doubt there was anything to be gained over the pres built-in to your interface (And as you've observed, the result might even be worse). 
 
If all you want is bit of warmth, there are tons of tube/tape effects out there that you can experiment with after you've recorded the vocal.

The Starved-plate design ART MP3 gets pillowy on bass, so maybe it is rolling off some highs - but I didn't use it that much on anything other than bass (it is in my live bag now as a splitter).  Other than the tube, it is a basic $10 preamp design like all the cheaper units and interfaces.  If you hear a difference in the recording, it could be doing something you like.  Or, something that doesn't get much press - hearing your voice through the unit "helps" your singing through the magic of a feedback loop.  It adds something to the sound, which you pick up on and change your performance (around the edges) that gets heard, and so on.

SilverBlueMedallion
I think the 2nd take isn't as bright on the "S" sounds.  Can anyone help confirm? 

Oddly, the test.wav plays back slow or pitch-shifted down. (???)
Regardless, I can hear less sibilance on the second vocal take so this agrees with your assessment. 

SilverBlueMedallion
so, is this typical tube behaviour?  Muffling up the "S" sound?

No... a quality tube mic preamp will not muffle the sound.
 
FWIW, I wouldn't bother with inexpensive mic preamps (tube or otherwise).  
You've already got those on your audio interface.  
 
GAP Pre-73 and Warm Audio Tone Beast are two relatively inexpensive mic preamps that are a significant step up from onboard preamps.
 
NOTE:
Guitar Center has the GAP Pre-73 mkII on sale today for $249 ($100 off).

So I just found out I shouldn't be using XLR cable from the preamp to the audio interface!   maybe THAT is my problem!  I found out I should be using TRS cables from the preamp to the interface, I will try this to see if it clears up the "S" sound.

TRS and XLR do the exact same thing. They are both balanced lines. The only difference is the connector. Changing from XLR to TRS will do nothing for you.

I think the confusion is the input voltage rather than cable type, if the pre amp puts out line voltage is best to use a line input (vice mic/inst input).