Do you have a chance to compare between these 300B-25 vs 2A3-S ?
Hi triode - Unfortunately, I've never hear either of these tubes. I've only heard EML's 2A3-mesh in a mostly stock Stereomour II, 45B in a Stereomour II converted for 45 tubes, and "regular" 300B ("regular" b/c it requires 1.3A filament current rather than the standard 1.2A) in a Beepre (modifed specifically for this tube) and Kaiju. So I've never heard different EML versions of the 45/2A3/300B family in the same amp. That would be interesting.
On that note, I wonder whether it would also be possible to run the EML 45B (note the "B", the regular 45 wouldn't work) in the MA. Assuming the low plate current setting of the MA is 50mA, perhaps it could be tweaked slightly downwards to 48mA to make the EML 45B work. Or maybe no tweaking would be needed -- the 45B appears to have more than double the plate resistance of the 2A3 at Jac's recommended 48mA plate current operating points. Perhaps this additional Rp would do the job of shaving a bit more current? ... And to better approximate Jac's recommended higher plate loads for the EML 45B, maybe one could install an impedance switch on the MA output transformers so that, for example, if using 8 ohm speakers, one could select 4 ohms on the impedance switch, thereby doubling the reflected load on the primary (Hmmm ... I may be talking myself into getting the MA amps).
cheers, Derek