The SYLVANIA JAN 5814A is a high-reliability tube, a military specification 12AU7A. It's also from the same lot, with the lot number 7021-BBE. I've built many preamps so far. I've used various 12AU7 and similar tubes, but the 5814A is still my favorite, in terms of noise and sound quality, at least to my less-than-perfect ears. This is a beautiful product, unused except for short-term testing when purchased as a spare for an amplifier. Please take a look at the photos and consider it for your amplifier.