Thank you for viewing. This is a Russian-made TUNG-SOL 12AU7W 6189 vacuum tube (dual triode matched). I purchased it new the week before last and used it for about 3 hours (swapped 3 times) in a self-made kit headphone amplifier. It's one of the tubes I bought together while searching for a vacuum tube that suits the amplifier. During listening tests with AKG headphones (using Belden cables), the sound is a bit bright but flat. It has a relatively modern sound, and I didn't feel any particular characteristics. The difference depending on the input line cable is easy to notice. If used with speakers, a wide soundstage can be expected. This is just my personal impression, and preferences may vary, but I hope it helps.