Modwright PH 9.0X Tube Rolling Question

Keep in mind, 5AR4 and 5R4 are very different electrically.  5AR4 drops 17V, whereas 5R4 drops 67V.  This means that the resulting B+ voltage available to run the audio circuit is 50V higher when using the 5AR4, compared to 5R4.  There are other differences in requirements as well.  Thus any difference in ultimate SQ could simply be due to the differences in these other parameters.  In some cases, the 5AR4 might stress downstream tubes served by the PS due to increases in plate voltage and/or possible changes in bias voltage.

I’m using the Sophia Aqua II 274B rectifier. Sounds pretty good. Wondering if I should try the Philips 5R4GYS?

Travis, I can only tell you that if you look up what tube rectifiers are cross-compatible with the 274B, the only tube that comes up is 5U4G.  I leave it to you to do further research. One other found fact: the 274B does not like to be followed by a filter capacitor of greater than 10uF value.  Many rectifier tubes come with a specification for the max value of the first capacitor following the rectifier.

This reference might help:http://www.fourwater.com/files/fullrect.txt

@travisg :"I’m using the Sophia Aqua II 274B rectifier. Sounds pretty good. Wondering if I should try the Philips 5R4GYS?"

YES !

Kristen at Modwright listed the following rectifiers:

GZ34, 5R4GYS, 5R4GY, 274B, 5U4, 5U4GB, 5V4, 5V4G, 5V4GB