Rectifier For Cary SLP 05

The 5R4GY is not a drop in replacement for the 5AR4/GZ34 as they have different electrical properties.  As to can you use a 5R4GR tube in your Cary, you will need to ask Cary.  The Mullard GZ34 is considered one of the best rectifier tubes you can buy and they last forever. 

Personally; there are only two 5AR4 iterations, that I would consider against the Mullard(Blackburn) GZ34.      Both, from Philips: https://www.ebay.com/c/168100339    and: https://tubeworld.com/gz34metal.htm    No connection to either reference.

@testpilot here's hoping it does last forever.
@rodman99999 how do the Phillips GZ34's sound vis-a-vis the Mullard?
@tvad I am checking with Cary on both the Brimar and the Mullard GZ37 nut as it is the weekend I thought I may get a quicker response here from folk who may have tried one.