LTA MicroZOTL tube upgrade

My experience with this preamp is vis a vis through my clients for whom I have re-tubed a couple of them so far.

A tube that will be hard to beat is the Brimar Triple-Mica Black Plate CV4024. Sometimes these will also be coded as 6060 or CV455, There are square getter and halo getter tubes and both are great. Probably $200-$250 matched pair. Holographic is the word everyone uses to describe tehes

Another tube that will be less warm and a bit more detailed//disciplined is the Valvo (Hamburg) Gold Pinned E81CC which is a premium (think 6201) version of the ECC81. Crystal clear, extended highs, controlled lows.  Also $225-$250

A wild card is the Marconi B309. I kind of consider the Marconi B309 the much younger (and much cheaper) little brother of the GEC A2900, one of my all time favorite tubes. $400+

If you want the absolute best, and this is the rare time in tube rolling where there actually is a best, get yourself some GEC A2900s, sit down and start hearing your music again for the first time. $1k-$2k

The 7062 is another geeky tube to check out. Avoid the halo getters,. DFOIL FTW.

What do you have for stock tubes?  I haven’t tried Ray Reserve, but they get good reviews. 

I’ve tried Brimar Yellow T 6060 (12AT7) and they are warmer sounding. Not what I wanted. 

My favorite tube is Telefunken ECC801S.  Second favorite are Siemens ECC801S.  Neither of these are warm.  

My stock tubes are Mullard 12AT7 M8161 and Radiotron Electron RCA.

Since I'm new to tubes, I assume these first ones have the biggest impact on the sound signature?

Both sets of tubes make a difference.  I first experimented with the input tubes.  I bought my preamp lightly used and the prior owner had already upgraded to the Telefunken ECC801S.  I ended up preferring them.  They're pretty pricey.  The Siemens are generally less expensive if you can find them.  Both are new old stock.  Both offer excellent detail and are in no way warm sounding. 

The 12SN7 or 6SN7 also make a difference. I think I'm currently using Sylvania Gold Brand 6SN7WGT tubes.  New old stock from eBay.  I've tried several different types of NOS tubes. 

I've got the latest microZOTL; I liked the stock 12SN7's. What I did need to change though were the stock 12AT7s - they were really holding the sound back to the point where I was ready to send back the preamp during the trial period. I told Jacob at LTA and he sent me a few alternatives to those, and 1 of them, tall Dutch Mullards, did the job perfectly and I'm very happy with the preamp now.