Air Tight 300B/WE rectifier question

Guys, need some advice. I know I should go to AXISS, the distributor for this amp, but thought I'd check here first. I run an Air Tight 300ATM 8W SET amp, with WE reisuue 300Bs, Chelmer CV491s (12AU7 drop ins), RCA red letter, grey long plate 12BH7s & a quite nice National Union 5U4 rectifier. Mpingo discs on the transformer casings and an Electrglide Fat Boy PC.

Itching to do something...I would love to grab a WE 274B off of ebay sometime, but not sure its an appropriate drop in for the 5U4 in the Air Tight (and think it might take a couple of years to get and answer back from Japan...)

I know a 274A or B is not a universal drop in for the 5U4, but would like some advice on what to look for to find out, assuming someone doesn't know off hand.

Thanks, Asa
I took a look at a datasheet I have for the 274A, in the book "Western Electric Tube Data," published by Antique Electronic Supply (now The 274A is a four-pin tube, and I assume the 274B is as well, while the 5U4 utilizes an octal socket.

Also, the 274A has a significantly lower output current rating, especially if used with a filter network that has a capacitor at its input (as opposed to having a capacitor just on the output side of the choke). The datasheet recommends that for capacitor-input filters, the capacitor on the input side of the choke be no more than 4uf. In that situation the maximum rectified output current rating is 150ma, for 450vrms applied to each plate. The corresponding ratings for the 5U4G, GA, and GB appear to be 225ma, 250ma, and 275ma respectively.

For a choke-input filter configuration, the 274A is also rated to deliver significantly less current than those 5U4 numbers, in the range of 160 to 200ma depending on voltage.

Hope that helps,

-- Al
Follow-up to my previous post: Upon further research, it appears that the 274B is octal-based, but as I stated the 274A is not. The A and B versions are identical electrically, according to the book "Tube Lore," by Ludwell Sibley, so my other comments apply to both versions.

-- Al
Thanks, Al. Good stuff. Thank you for your efforts. It sounds like not enough current in the 274B for my application. I had that feeling, but REALLY wanted someone who knew to tell me, hey, go right ahead. Apart from going for an original matched pr. WE300Bs at $2-2.5K per crack, I've sort of maxed this amp out.

Any other comments are, of course, humbly appreciated...