I've just read through this entire thread, having been referred to it by Tmmvinyl today in another thread. Charles & Bill (Brownsfan), thanks for the nice words earlier in the thread.
After examining the
Elrog 300B datasheet, and comparing it with a 1939 Western Electric datasheet I have (as reprinted in the book "Western Electric Tube Data," published by Antique Electronic Supply), and also with a
datasheet for the Psvane 300B-T (click "additional images" and then "enlarge"), in lieu of a datasheet I couldn't find for the non-T version which I believe is what Israel supplies, I agree with some of the others that there is cause for concern operating the Elrogs in the Franks.
While the specs for the vintage WE 300B and the Psvane 300B-T look extremely similar, as was alluded to earlier the Elrog tube has substantially lower transconductance and amplification factor, substantially higher plate resistance, lower output power under similar operating conditions, and correspondingly different parametric curves. It also has a considerably higher (better) maximum safe plate voltage rating.
I'm not 100% certain, but I believe that the net effect of these differences will be to cause the Elrogs to self-bias to significantly different bias points in the Franks than the Psvane or original WE tubes would bias to, and in the direction of being more stressful. And based on a quick look at the disparities between the numbers, I'm not sure that even changing the 1K resistor to 1.2K would be enough of a change for comfort.
Charles, what I would suggest is that you follow up the response from Israel, in which he cited the 400V and 28W numbers, by providing him with a link to the Elrog datasheet and asking him if he can provide a rough indication of what those numbers, and also the bias current, would change to if Elrogs were used in place of the Psvanes he supplies the amp with.
Also, unrelated to that, I'm wondering if Mk (Matthias) can provide a link to the WE datasheet from which he gets the maximum ratings cited for the WE 300B in his post above. Rather than the 36W and 400V numbers he cited, the 1939 datasheet I am looking at specifies "limiting operating conditions for safe operation" (what would probably be called "absolute maximum ratings" today) of 40W and 450V. Although it is made clear that those conditions and the 100 ma max current spec for self-bias should not be considered to be simultaneous. And a separate table defining numerous possible operating conditions indicates maxima of 450V @ 80 ma, which does correspond to 36W. But still, I don't see how to reconcile the 450V number I see in the datasheet with the statement by Matthias that "the old datasheet of the 300B says 400V Anode voltage as MAXIMUM."
Best regards,
-- Al
