Look forward to the Tortuga/Saga comparison you got coming. Rolling tubes in the Saga is a subtle but noticeable difference. I’ve tried Shuguang Black Treasure cv-181-z and a Sylvania vt-231 and both are excellent with the vt-231 being the preference so far in my system. I just ordered a Sophia Electric blue glass 6sn7 so hope it brings the magic the way their aqua 274b rectifier does.
Here's the comment that got me thinking seriously about the Saga:
"I auditioned the latest version of the Tortuga passive preamp, the $1195 LDR3.V25 and had a Schiit Saga to compare with at the same time. The Schiit Saga was more transparent than the Tortuga, which sounded coloured to me and after extended listening even somewhat fatiguing.
Tortuga Audio does not list distortion figures for their preamps on their website but the distortion of the Tortuda LDR3 has been measured: at normal listening levels THD is about 1.0% and IMD is also high at 4%. These are unacceptable distortion levels for a modern preamplifier. In comparison the $349 Schiit Saga THD and IMD both measure less than 0.002%. Recommend you try the Saga first, it even has remote control.
I prefer to buy tubes made from 1940 to 1970 when tubes were king and the manufacturers had their processes and secret sauces down pat. The new Tung Sol 6SN7GTB offered as a $25 option for the Saga is OK, nothing to get excited about, very warm sounding. Trying a handful of NOS tubes my favorite lower cost option is the 1951-1953 Sylvania 6SN7GT Bad Boy, if you are patient you can get a three rivet hole for about $70 on eBay. Nothing I have tried sounds better than a 1940s Tung Sol 6SN7GT though. I managed to grab a few before the prices shot up. The Saga is great value I have compared it to preamps costing four times as much and preferred the Saga. I use mine between a Yggy A2 and a Kenzie tube amp"