Best 3A5 / DCC90 / CV808 tubes?

I don’t recognize any of those alphanumeric codes. What is it? Is it a 2A3 with an oddball filament?

The 3A5 designation means "3 volt heater, 5 element/pentode structure". This is a new one for me! I will have to take a look at my GE tube manual.

It's a double triode tube. There are plenty available cheap on eBay right now.

Sure, but are they any good? There's not really much information out there from searches I've done, at least, from users on if there were any they preferred, etc.

It's meant for a high frequency oscillator use, at frequencies up to 40MHz, according to the data sheet.  Jason, I don't know what made you think it had to be a pentode, with the designation 3A5.  Not that it couldn't be, but why did you think it had to be?

mmcgill829, What do you own in the way of audiophile gear that uses this type of tube? Apart from its very high frequency bandwidth, the other specs are not remarkably deviant from standard audio triodes.  And the spec sheet does not indicate how it would operate in the audio band.

@lewm Allnic DHT D-5000 DAC

There are plenty of 3A5's available on Ebay. Some are in boxes and presumably new. Prices are low! You could buy and try a bunch!

You can also buy them from reputable vendors. eBay is a crapshoot when it comes to tubes. I’d stay away entirely.

quick update - I bought a few different types and experimented with different ones and there was a near zero discernible difference in sound, so any old one should do. :)