Looking at these specific preamps give me your opinions

I have a LTA MicroZOTL preamp.  I had two different conrad-johnson preamps before that.  I'm using it with single ended interconnects to a Coda solid state amplifier.  I'm very happy with it.  I thought I'd miss the warmth of the cj preamps, but I really don't. I feel that it's better than the cj. 

@cbrez ​​​​​​

I bought my MicroZOTL preamp lightly used and a little over a year old.  The previous owner said it came with Trigon 12AT7 tubes. I tried them and didn't like them.  He had purchased some Telefunken tubes {not cheap} and I bought them with the preamp.  I've also tried Philips, Siemens, and Brimar Yellow T.  Siemens came in a close second to the Telefunken. These are all 12AT7 type tubes. 

@gregjacob I'm using the same Telefunken ECC801S.  They are the most detailed and best sounding in my system. A friend thought they were too bright in his system. The Siemens ECC801S are very good, but a hair less detailed. A fair bit less expensive, though.  The Brimar Yellow T are nice and warmer sounding if your system is already on the bright side. 

I haven't heard the Raven, but what I've found with the LTA MicroZOTL is that the sound quality is greatly effected by tube selection. Mine originally had Trigon tubes which honestly sucked.  Telefunken and Siemens tubes were tons better.  Brimar Yellow T are also good, but on the warmer side.