WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
This can be done, however, I believe the 6X4 has a lower current rating. The device that had the 6X5 in it may draw too much for the 6X4 and it won't last very long. Most of the time you can get away with this fine for a temporary substitute but don't expect reliable service, even though you may end up getting it.
hmmm, I was kinda wondering if one had a noval base and the other an octal. I remember now but I didn't then. In that case, I remember waht a 6X4 and a 6X5 are and a bit about their numbers. The 6X4 is very small and low powered compared to a 6X5. They aren't even close in current ratings anyway.
well i bought an amp recently which uses a 6x5 for a rectifier. then i was browsing the net and read somewhere that a 6x4 can be substituted in. so i was wondering if the 6x4 could be a better substitute(apparently not) because i hear the 6x5 is pretty weak itself.
If you want a powerful substitute, try a 5r4, it's much bigger but it'll work well in there. That's what I do with some of my amps when I upgrade them. I had a 6V6 amp and changed it to 6L6's and just gave it a bigger rectifier tube and output trannie, it worked well. What kind of amp is it you've got?
Have a look at a pair of 6N3's or EY82's. If I remember a 6CA4 correctly (haven't seen one since the early seventies) the 6N3 is like one of these but with one large single anode instead of two half size ones. They were sometimes used as a pair in B/W tv sets. Used to use them to make junkbox amps when I was a broke teenager. http://w1.871.telia.com/~u87127077/diod/ey82.htm
6AX5 will plug into 6X5 socket and it is higher rated. HOWEVER, it does have a higher filament current and would put additional load on your filament transformer. If the transformer has the capacity, it would be a good choice.