@sls883 , Hi , I’m late to the game but my thoughts on your tube thread. Congratulations on the LTA, I’d love to try your preamp. So I saw your comments on your tubes. I have some long term experience with 12AU7’s and some of it carry’s over. Having recently acquired the Rogue amps , they use a 12AX7 as an input/ phase splitter feeding a pair of 12AU7’s. They used to provide NOS with the Dark upgrade consisting of a TFK 12AX7 and a pair of RCA 12AU7’s. Unfortunately due to cost , availability and reliability they go with PREMIUM new production tubes. So I received my amps with new Tung Sol 5751’s a lower mu 12AX7, and new JJ 802s gold pins. The JJ’s are lipstick on a pig and went straight into the parts drawer. The Tung Sol’s were replaced with a pair of NOS TFK’s curve tracer matching from Brent Jesse at $318 for the pair. As an ardent TFK fanboy I was disappointed with them in MY application. Looking back the Tung Sol’s at $45 each are surprisingly nice. I then went to GE 5 Star and have some Gold Label Sylvania’s to try. The 12AX7’s as a whole are widely used in many applications and unfortunately popi drives prices through the roof. The other thing to consider is there are about 3-4 lower Mu replacements for the 12AX7, the 12AY7, 12AT7, 5751 are all lower mu ( gain ) replacements. However I have no idea what might work , so ask LTA if you go that route. But with the thread discussion of exotic NOS tubes, in 12AU7’s I have TFK Tektronix branded and the holy grail G73-R black coated version. In Seimens I have the Nickel plates and CCa. My experience is the TFK’s sound the same but are a higher medical or industrial graded tube. The Nickel Seimens are brighter than the TFK’s or the regular Siemens. I actually purchased the G73-R’s on EBay for $125 each 7-8 years ago. Todays scarcity and forgery’s have me mostly at Brent Jesse and Arizona Tube Supply Andy at Vintage Tubes is highly regarded and I’ve occasionally purchased from The Tube Museum. The other thing I found out in regards to small signal tubes is I’m not a Mullard fan. To me they sound like a blanket over my speakers. However that is the basic E82CC and I have not tried their good stuff and the experts absolutely rave about them. Currently The Tube Store has Mullard 10M 12AT7’s nib for a good price, but check with LTA as to how the low Mu variant will fare. My two cents , Cheers Mike B.