Elrog 300B vs Takatsuki 300B tubes

Hi Bill,

The upshot of my previous post is that if no one participating here has already done so I suggest that one of the Lampi users ask Lampi if each of the various rectifiers that have been discussed is suitable for use in the Big 7 and the GG. And that Lampi also be asked if the filaments of the output tubes and the rectifier tube in those DACs are supplied by the SAME 5 volt output winding of the power transformer. As opposed to the filaments of those tubes being supplied by separate 5 volt windings in the power transformer.

If the answer to the latter question is "yes" I would recommend against using a rectifier tube having less than a 2.4 amp filament current at the same time as an Elrog 300B is being used. If the answer to the latter question cannot be obtained, I would suggest that there is a non-zero risk in doing so.

Best regards,
-- Al

Thanks Al. Got it.

Hello Al,
A directly heated triode requires it's own dedicated filament winding unlike an indirectly heated triode. If you look at the bottom of a power transformer(not a plate transformer mind you)you will see individual windings for the output, signal & rectifier tubes. Indirectly heated driver tubes such as the 6sn7,6sl7 etc can share a 6,3v/2 amp winding. Of course the rectifier tube has it's own winding as well. It's typically 5v/3a.

You can use a 5v/2a tube on a 3 amp winding, but you can't use a 5u4g on a 5v/2a winding. Since this thread is largely about the "Franks", lets try to keep in mind that these two circuits are completely different from one another, and that we don't have a "one size fits all" situation here. Hope this sheds some light up here.

Best,

George

Hi George thanks for chiming in. So as far as Elrog 300B in Lampizator Golden Gate DAC is concerned, a rectifier that draws 2A/5V is fine (assuming GG DAC has a separate 3A winding for rectifier tube)?

Yes, thanks for chiming in, George. After thinking about your comment I agree -- the 5 volt winding for the directly heated 300B and the 5 volt winding for the rectifier must be separate, or the circuits wouldn't work properly. Thanks for pointing that out.

I'm still a bit uncertain, though, that it would necessarily/always be appropriate, with respect to long-term reliability, to use a 2 amp rectifier on a winding that is designed with the expectation that it would be used with a 3 amp rectifier. My concern, as I mentioned earlier, being that the filament voltage provided to the rectifier would increase to some unknown degree compared to the voltage that would be provided to a 3 amp tube, due to the lighter loading on the winding.

Thanks again. Best regards,
-- Al