Elrog 300B vs Takatsuki 300B tubes

Charles, George said I should have no problem using the tubes in my amps. Yours are older then mine, make sure the cathode resistors are the same and the rest of the values didn't change.

Best,
Joe

Hi Charles,

My only knowledge of the 300B operating parameters in my VAC Renaissance 70/70MkIII consists of the values Raquel provided in the thread I quoted from earlier. In which he said that the plate-to-cathode voltage is approximately 430 volts (compared with 484-79 = 405 for the Elrog in this case), with an idle current of approximately 85 to 90 ma (compared with 77 ma for the Elrog in this case). Also, based on those numbers for my amp, 90 ma x 430 volts = 38.7 watts plate dissipation.

The numbers George measured for the Elrog seem to me to be moderate.

Best regards,
-- Al

Al and Joe,
Thanks much! These measurement findings do suggest that the Elrog tube should be fine in the Frankenstein amplifier. Al your selected 300b tubes must be vefy rugged to tolerate the parameters in your amplifier and provide the durability and longevity they do I need to measure my wall outlet AC voltage to be sure that it is not excessive.
Charles,

All, my AC measures 122.1 V. I got the same number last week as I did last November, so I am a little concerned regarding tube longevity in my Frankensteins. I did check to verify I have no red dots on the cathodes. My power company will not address the issue unless the voltage is outside of 120 V plus or minus 5%.

I guess there is a silver lining to not having much listening time for the last couple months. Until if figure something out, I can reinsert my Psvane T's so that the Elrogs aren't compromised.

I have followed the thread since its inception, and am most grateful to all those doing the heavy lifting on sorting through this. However, I am uncomfortable allowing the 122. 1 V situation to stand "unrectified." Were I to utilize a variac, I would probably require two due to my AC wiring configuration. Any recommendations on a relatively inexpensive variac? How about using one of the PS audio power plants with the Franks, which would require some limited room rewiring?

07-07-15: Brownsfan
My power company will not address the issue unless the voltage is outside of 120 V plus or minus 5%.

That is the standard in the USA for household AC, as measured at the service entrance. The upper limit of that range corresponds to 126 volts.

With due respect to George, I must admit to some skepticism about the requirement of 122V max. I would expect that the designs of the power supplies in equipment marketed in the USA would in most cases be targeted to supply optimal DC voltages to the tubes and circuits for an AC input of exactly 120V. And I find it hard to believe that an increase of 1.67% from that figure would be the upper limit of acceptability.

Also, I don't see how a statement as specific as "over 122V AC is a game changer for these or any other 300B tubes" can be defined in such a universal manner, apparently with applicability to all 300B-based designs, given that I would expect significant variation among different designs in the +/- tolerances of the transformers and other components in their power supplies. Not to mention in how hard the tubes are driven.

Best regards,
-- Al