Other Rectifier tubes Alternative for 5AR4

5U4G sounds better than 5AR4, in my amp at least, but don't risk damaging your amp if it says 5AR4's only.

The reason I asked is that I have a Musical Paradise DAC which states that I can roll all those different tubes.

In a DAC the current draw will be minimal (most rectifiers can handle the output section of an amplifier) so a wider variety of tubes can be used- the outcome will be that the B+ voltage will be slightly lower.

It’s not an issue in this case since you have directly heated cathodes, but the 5AR4 also has a controlled warmup time to prevent cathode stripping. At any rate there aren't any good subs for it.

Do you mean my amp which is based on the Luxman MQ-300 is directly heated cathodes, so, I need to use 5AR4 where it has a controlled warm up?  And I can’t use a 5R4 because it doesn’t have the controlled warm up?

No. I mean that in your amp that quality won't make a difference. Cathode stripping is a phenomena of indirectly heated power tubes. Your power tubes are directly heated (the filament is the cathode literally) so cathode stripping is impossible.

Late to this thread. Just today, I spoke with the authorized Luxman warranty tech, Mike Garry, about replacing the 5AR4 with a 5UG4 in the MQ-300. He said do not do it. The amp's huge power supplies have an inrush that could be too much for a 5UG4. Or something like that. Glad I asked because I just bought an MQ-300 and I have a stash of nice 5UG4 that I would have tried in it.