name that tube

>>No, but 5V4s and 5Y3s are basically interchangable<<

No, they are not.

For example, 5Y3 is a popular rectifier for 2A3 amps and 5V4 for 45 amps.

Now, using your assertion, stick that 5Y3 into the 45 amp and watch the snap, crackle, pop action of your triodes.

Very bad information.

Audiofeil,

I know you know much more about tubes than I do, but I'd always read (or at least thought I had) that you could use a 5Y3 with either a 2a3 or 45, and that it is the 5v4 that should not be used with a 45 triode.

Am I mistaken?

Try putting the tube in the freezer for a while, sometimes the markings that have been wiped off will show up in the frost.

Sorry, Darosenb my post is in error. The idea was correct but the typing was not.

An amplifier manufacturer I represent vigorously cautions against using the 5V4 with a 45 as you point out.

The 5Y3 is appropriate for the 45 Triode and could work with the 2A3 in many circumstances.

My bad.

Don't try this at home.

???? What? Are you guys kidding me???????

Audiofeil, why don't you explain to me the electrical mechanism by which a 5Y3 will make a 45 "snap, crackle, [&] pop". Does the 45 look around, and upon seeing another directly-heated cathode . . . commit some sort of spectacular suicide out of jealousy? If anything, the 5Y3 is the one to exhibit higher stresses, and if you were pulling something like 100mA, then a 5Y3 wouldn't last very long, but a 5V4 wouldn't last a whole lot longer.

So again, what current levels are we talking about for a 10W SET amp? A 5Y3 can withstand years of hard use in a Fender Princeton, Harvard, or Vibrolux, at like 50-60mA, 400-ish volts. 5V4 is a VERY common sub for these applications that gives a tiny little bit more volume and crunch. I've even seen people getting cheap and using a 5Y3 instead of a 5U4 in Supers and such . . . not really a very good sub, but it WILL play for years this way, and unless somebody over-fuses the amplifier . . . no damage will be done, even if it fails.