The 5AR4 has a controlled warm-up characteristic, but otherwise handles conditions similar to the 5U4. The voltage drops are a little different too.
Generally if a 5AR4 is in an amplifier you can count on it being there either due to space considerations or the designer is being sensitive to the damage that will result to the power tubes if the B+ appears immediately, which is what will happen if a 5U4 or similar is used.
So don't try to sub it if you like your power tubes.
Generally if a 5AR4 is in an amplifier you can count on it being there either due to space considerations or the designer is being sensitive to the damage that will result to the power tubes if the B+ appears immediately, which is what will happen if a 5U4 or similar is used.
So don't try to sub it if you like your power tubes.