Preamp Rectifier Tube Confusion

+1, on the Mullard (Blackburn plant) being the most reliable and longest lasting, GZ34/5AR4.         You should most definitely contact Kevin Deal, at Upscale Audio, regarding whether a rectifier change will make an audible improvement, in your Primaluna gear.      He has much experience with the brand.      https://upscaleaudio.com/pages/contact-us

5AR4 and GZ34 are the same tube. I think that the Mullard is the best I have heard but the Matsushita made 5AR4s are actually very good. I am not a fan of substituting different tube types and would stick with the rectifier around which the circuit was designed. 

@jl1ny 

However, the Primaluna manual lists compatible tubes as: GZ34, CV1377, 5V4G, 5T4, 5Y3 and Upscale Audio also list the Philips 5R4GYS.

My bad, I see now you are saying that the manual lists the above tubes as compatible IN ADDITION to the 5AR4.

I had read somewhere before what atmapshere is saying, that different but properly working rectifier tubes should not change the tone of a preamp, and I also believe the same for an amp, such as my Dynaco ST-70.

When I purchased my Mullard 5AR4 a number of years ago, they were reasonably priced, and they last forever and a day.  Its one and done. 

I have a "preferred series" (supposedly a "select" ShuGuang) 274b from thetubestore. Not sure if it improves the sound of my small single ended amp, but it sounds great and the tube simply looks cool so that makes me feel better about the whole thing.

I reached out to Upscale and their response was: “I cannot give you an endorsement or recommend it, but it does say it is an equivalent”.

Im curious to see the performance stats of the WE274B compared to 5AR4.