Why Can't Modern Tube Manufacturers Make a Proper Tube?

@jtcf decooney I am thinking the same about how many people have actually tried several new production tubes before dismissing them as sounding horrible...

Yep. I’ve not let go of my best Mullard, Sylvania, RCA, Tungsram vintage tubes yet (keeping them hoarded away for no good reason), my preamp and mono tube amps now run all current new-production tubes. Tubes from Psvane, TJ Full Music, and Tung Sol too. With patience, i’ve found some (not all) new production tubes can benefit from letting them burn in for 100+hrs. It can make a nice difference. True for my 6SN7s, 12Au7s, 12At7s input/driver tubes, and, KT120, KT150 output tubes. As many of us have learned through experience, buying new tubes from a trusted seller who actually tests and ranks their tubes matters too.

Many Modern tubes are pretty good, if you buy from sellers who thoroughly test and match them.  They identify a lit of rejects that way, and guess what? Somebody else sells those rejects.   If you’re looking for a “good price”, guess which tubes you get. 

@decooney I run Harbeth 40.3 XDs with a Rogers High Fidelity EHF 200 MK2. Sounds really good, drives them with ease.

As many of us have learned through experience, buying new tubes from a trusted seller who actually tests and ranks their tubes matters too.

It does, (goes for new and NOS) and if you are running tubes like KT150’s new Tungsol’s are the only option. However Roger said the reject rate is pretty low on the 150’s, but not definitely not 0%.

I've got contemporary WE 300B's made in Georgia (the state, not the country) - those are awesome tubes that made my amp sound like an upgraded model, if there's been one. Expensive indeed, but worth it if it's what you like. 

I have been running 8 A-matched Sophia Electric EI-34’s in my Primaluna and have been very pleased with them. Not cheap though.