Telefunken and Mazda (silver plates) 12ax7 are great if you want to amp up detail. The smooth plate Teles are warmer; ribbed plates are a bit more dynamic but also touch brighter. Mazda silver are the best omg - but a tad bright and expensive! The Trumpet MC is warm overall so it’s very accepting of these tubes, more than most.
I don’t have much for 12au7 in my collection but I do have British Mullard CV4003 in there now (warm) and the result with brighter more detailed 12ax7 is quite nice.
Modern Russian production tubes are really quite good too. The Mullards are quite warm. The Tung-Sols give you a bit more detail and energy up top and I like them in the Trumpet MC. The overall tonality/balance of Russian Mullards and Tung-Sols actually tracks pretty well with their vintage counterparts.
Teles are expensive from “trusted” sources but they’re really quite common. So many of these were imported to USA, e.g. in Fisher gear. No need to overpay for Teles. Find a few “used tests strong” pairs and keep the best. Of course this works much better if you or a friend have a tube tester.
I’m not really a fan of RCA tubes but they’re OK, sometimes. GE triple mica black plate 5751 are much better than RCA 5751 but I haven’t tried a 5751 in the Trumpet MC yet. It’ll certainly work, but not sure how the sound will be.


