5R4WG tube

Which is the best?

5R4WGA, 5R4WGB or 5R4WGY.

I forgot...
I have to use on Quicksilver Silver mono kt88 (90watt)

You have compared this type of valve with GZ34?

Don't change the rectifier tube from what the amp was originally designed for! Rectifier tubes drop different amounts of voltage - this will alter the B+ voltage from what a particular circuit requires! Plus the heater's current draw may exceed the safe limit of the power transformer (cause over-heating!).

Don't think that you are smarter than the circuit designer and play around with dissimilar rectifier tubes! This can lead to a damaged amp!
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