It's funny how I sometimes read something that alerts me to stuff that I have in my stash that I discounted as crap decades ago and never even tried. I was reading a write up on the Amp Garage about preamp tubes and the author had included a write up on the 80s/90s Beijing Chinese Military Square Getter Triple-Mica 12AX7 . He went into some detail about them and said "these older production tubes sound nothing like the newer mass-produced Chinese Shuguang 12AX7s, which can have a very harsh and unmusical tone". These are the famed early '90s tubes Marshall and Mesa used that a lot of guys like. Anyway, I got a new piece of gear back in the early '90s that had the 12AX7A in it which I promptly ripped out and replaced. It's been sitting in my tube bin since. I also acquired 40 NIB National branded 5751 tubes a year and a half or so ago from a customer of mine. They used them as spare parts in old equipment but had not used any in many years so they ended up in a list of parts they were looking to liquidate. When I saw them on the list I was dreaming of finding a big score of vintage glass but when I pulled their purchasing records I saw that they were part of a 50 pc buy they did in 1993. They still had all 50 but wanted to keep 10 just in case they needed a few. I had a few of them tested on a high end computerized tester and the test results indicated that they are high gain 12AX7's that were likely just labeled as 5751's. I sold off most of that lot to a popular tube dealer and traded some with dudes on forums. I had tried them in a few of my amps and didn't really like them in the amps I tested them in so I didn't really care to hold onto many but kept a sleeve for utility use. Anyway, I was just comparing one of those with this Beijing tube and I'll be damned if it isn't identical in every way. I had previously only tried them in medium to low gain amps and have since acquired a Peavey 6505+ and decided to give them a try in a high gain amp. I pulled vintage Mullards I had in V1 & V2 and stuck in the Chinese glass. At first I thought, not much difference....why waste the mules, I'll leave these in. Then I cranked it. HOLY SMOKES!!! Now I know why guys love these in high gain amps. Here is a short low volume clip recorded with a cell phone. The amp was set to the red channel with the gain at 3. I went straight in with a Les Paul Standard and had a Digitech DL8 set to loop and a Hall of Fame reverb in the EFX loop. It's a BEAST when you crank it. I haven't had a chance to mic it up and record a clip of that yet but plan to later this week.