Single 1M vs dual 1M bootsrapped master?

[John_P_WI]

Always good to see your and Gingertube's posts; I miss powerscaling.com forum.

Best regards,

Steve

Hi Steve,

Yes, always good to see your posts and Ian (Gingertubes) as well. It is too bad that the power scaling forum vaporized in such a manner as it was such a great forum for thinking "outside of the box" with an unlimited potential for learning. I for one would have loved to have archived some of the info, guess it is only my fault.

Staying on topic, this gives me an idea, I'm currently in the process of laying out a D style pcb with distributed filtering etc. I think I'll add in a couple of extra pads on both sides of the LTPI 1M grid leaks to parallel a dual pot for the "improved boot strapped master". If I have enough room, I'll add pads for a relay too and play with additional switching...

Take care my friend, Happy Holidays.

John

[John_P_WI]

Dbl

[ampdoc1]

Jazbo8,

I believe that the cathode poisoning idea has been debunked. If I remember correctly, that is applicable only to transmitting tubes. Dropping the B+ enough on the output tubes would require some large resistors, or pot.

The amp I reference was built in 2004 and is still running on the original tubes.

Try my solution before you pooh-pooh it! It'd probably take about 10 minutes to rig.

a'doc1

[martin manning]

Cathode stripping is not likely to occur with receiving tubes. From the Valve Wizard site:

"The theory is that if the HT is applied while the cathodes are cold they will be 'stripped' by ions crashing into the unprotected cathode. However, this simply does not happen. It is an urban myth borrowed from transmitter and cathode-ray tube technology NOT ordinary 'receiving' valves."

"On the other hand, leaving a cathode hot without any anode current flowing does lead to the very real effect of cathode poisoning, which reduces the gain (transconductance) of valves. Fortunately this phenomenon really only becomes significant if the valves are left on standby for hours on end. "

On the OTHER hand, if the filament voltage is significantly reduced, the cathode is much less hot.