Damien, glad you had a chance to try the 12AT7 option in your amp. I  also like the "AT" series in my 2006 era Taboo, always coming back to it despite slightly lower input sensitivity. A word of caution with respect to using 5Y3 rectifiers in both the CSP and Taboo however. Most 5Y3GT's produced after 1955 were designed to work OK into a 20uf filter input cap; the older CSP and Taboo used 33uf power supply input caps, a design compromise which allows for the use of several different rectifier types, but which puts some strain on the 5Y3's and tends to shorten their life span. (When they give up the ghost the fuse generally blows.) The older pre 1955 5Y3G / GT's, although wonderful sounding, are even more delicate since they were designed to load into 10uf caps and I have found tend to have much shorter life expectancy unless the power supply is modified to  accommodate them. Generally the SOVTEK 5Y3's that Steve supplies are a bit more rugged and last longer than other 5Y3 NOS choices. There is less of a life expectancy problem with the 5U4's and 5AR4's which were designed to load into 40uf to 60uf power supply input capacitors; they will occasionally blow, but this tends to be an individual tube quality issue.  8-)  Walt

It is certainly possible for a rectifier tube to last a very long time, even the lifetime of a given amp or beyond, if it is used according to the tube designer's specifications in the design of the amp. I guess in this context any rectifier failure would be considered a shortened lifespan. Based on the handful of schematics I have seen of Steve's amps, his power supply designs seem to favor the use of 5U4's and 5AR4's. Personally, over a period of over 7 years during which I have rolled many different 5U4's, 5AR4's, and 5Y3's in my three Decware amps, I have experienced five 5Y3 failures (three of which were the older 5Y3G) and one 5U4 failure. I do have high power company AC voltage in my area which likely also contributed to this.

I have had one rectifier fail and it was a 5U4 but it was bad from the factory so I don't think that should count