These are the latest generation of 12AT7 valve to come from the Electro Harmonix plant in Russia. The main improvements made are in the area of microphonics and noise. This is very different to the Standard 12AT7EH. The most prominent changes that I noted when I audio tested it was the added clarity that this tube seems to bring out. The tube will directly replace any standard 12AT7 or ECC81 tube and is a worthwhile upgrade to any amplifier. The design improvements made to this tube from the standard ECC81 are set to make this WC version a number one choice.