The NOS Mullard 12AT7WA / CV4024 is, IMO, the best tube on the market to put into the PI. However, at $50 that can be a though pill to swallow. Coming in at a close 2nd, the EHX 12AT7WC. Unlike the NOS Mullard, this price on the one is much more reasonable.
A very well built tube, the 12AT7EH will excel in any guitar application as well as in Hi-Fi applications.
The very dynamic and deep low end response of the long plate EH 12AT7 tube makes it an excellent choice in reverb driver and phase inverter stages. However, use in high gain preamp stages is not recommended due to potential microphonics.
• Extra-low microphonics makes it the best 12AT7 choice for reverb circuits. Also suitable for HiFi.
• Factory selected for closest tolerances and most consistent performance
• ECC81 equivalent
Electro-Harmonix tubes are all new designs and are of excellent quality. Many OEMs use relabeled Electro-Harmonix vacuum tubes in their amplifiers. If you want great sounding tubes at a very reasonable price, then Electro-Harmonix tubes should be on your list.