What are equivalents for 12au7, 12at7 and 12ax7 tubes?

_{Our preamps work well with any power amp, whether it is a solid-state power amplifier or a tube power amp, because we have exceptionally low output impedance and our other parameters are very much middle of the road. Our tube preamplifiers are made with no screws showing and no vent holes, to emphasize the clean design of our chassis. In our linestage preamps, we only use 2 tubes, which are 12au7 and of course any 12au7-equivalent, which means that it is easy and affordable to experiment with different tube brands to achieve the sound you are looking for because the 12au7 is one of the most plentiful vacuum tubes on the market. .}

_{For those who are curious about the advantages of solid-state vs. tube designs, we have created a Preamp Blog that addresses many different questions, including whether it's good to use a solid-state power amp with a tube preamp. The Blog also talks about which tubes sound the best, and whether it's necessary to learn about NOS tubes in order to get the best sound quality. We believe the best tube preamp in the world is one which allows users to experiment with vacuum tubes *or* to simply listen to music without even thinking about vacuum tubes, if that is the user's desire.}