I use "Yugo" tubes in a couple of pieces of equipment. They are also known as EI and were made by EI.
There are more than one model 12AX7. The one most folks refer to has a long grey plate and is modeled after a Telefunkin. A very nice clean/clear balanced tone but I wouldn't like it, I think, in a system already on the edge of brightness. It wouldn't warm it up much.
The other I use has a short(er) grey plate which has a little less high frequency energy and a more mellow tone. Each type serves a purpose and it depends on the equipment as well as synergy with other stuff in your system.
FWIW.
There are more than one model 12AX7. The one most folks refer to has a long grey plate and is modeled after a Telefunkin. A very nice clean/clear balanced tone but I wouldn't like it, I think, in a system already on the edge of brightness. It wouldn't warm it up much.
The other I use has a short(er) grey plate which has a little less high frequency energy and a more mellow tone. Each type serves a purpose and it depends on the equipment as well as synergy with other stuff in your system.
FWIW.