Notes on Tubes
All of the new production preamp tubes out today seem to have at least one characteristic or another that isn't quite right compared to the NOS American and European made tubes.
NOS preamp tubes such as RCA, GE, and Mullard are unbeatable. But, these are very expensive, so it's not always possible to use them. We have found the JJ 12AX7s to be one of the best new production tubes available. No, they are not perfect, but as stated, none of the new production tubes are. JJ's 12AX7 is one of several designs based on the wonderful German Telefunken. They seem to have the best combination of tonal characteristics, low microphonics, and reliability of any of the 12AX7s available today.
If you want to go the NOS tube route, there are many knowledgeable and reputable tube vendors on the net.
JJ 6V6s also seem to be about the best new production 6V6 tube available today. They have a nice lively tone, are very reliable, and can handle high voltages with ease.
There are several excellent 6L6s being made today. The Groove Tube/Fender 6L6GE is a copy of the short bottle GE 6L6, made on old GE equipment, with a percentage of NOS parts. With its nice breakup, and shimmering clean tone, it is about as close to NOS as you can get.
New tubes tend to sound their best after a short break-in period of five or so hours.