NOS 5Y3s

How good are the Sylvania and the RCA 5Y3s compared to the JANs? Are they all basically the same?

I've had good results with all of them.Rectifiers are very basic,they just supply DC voltage to the amp.They either work or they dont.When talking about 3 different brands of the same type of rectifier,one isnt going to "sound" better than the other,they are not in the signal chain so they have no effect on tone.Now if you used a 5V4 in place of a 5Y3 you may "percieve" a tonal change,but it really isnt the tone that changes,it is the response of the amp,the 5V4 will stiffen the power supply some and have less sag,and make the amp sound tighter.Any of the NOS are better than the current production because they can take more abuse and will outlast them.So,in my opinion,any of the ones you mentioned will be fine.

That's the kind of answer I was looking for. I'm starting to stockpile tubes and have found that prices on the NOS Jan tubes are twice as high. It's good to know they'll all work fr me.

If you plan on using these in your LSS,I would advise using a 5V4.The LSS tends to be right on the edge for the limits of the 5Y3.In fact,not sure if they still do,Mesa would replace the rectifiers free of charge when they blew,which they did often.Most old stock 5Y3's could handle the extra stress,but,in my opinion,its still not good to operate a tube so close to its limits.The 5V4 will work fine in this amp,and you probably wont notice much difference,maybe a bit tighter bass,which isnt a bad thing.

I'll keep that in mind. So far I haven't had any problems but its good to know there are better options.