Power Cables

Sisyphus51 6-14-2018
A IR voltage drop of two volts across a very long power cable will not cause an equal 2 volt drop in filament voltage in a vacuum tube amp.

Of course not, and no one has said that it would. In designs in which filament voltages are unregulated the drop will be essentially proportional. 2 volts/120 volts = 1.67%.

In tube datasheets I’ve seen which provide +/- tolerances for filament voltage (and many of them don’t) the specified tolerance is usually +/- 5% or +/- 10%. And I see no reason to expect that performance would be identical or even particularly similar throughout those tolerances. 1.67% is not an insignificant fraction of those tolerances.

Regarding your other comments, Ralph was of course not saying that the extreme example he cited represents typical performance for most or even many designs. He was citing that example in support of his explanation of why power cords can make a difference. And if a person like Ralph says that "depending on the amp this can be pretty profound. and I have seen it with my own eyes," that’s good enough for me.

Regards,
-- Al

Quote: Ralph K. " I’ve seen a 2 1/2 volt drop rob an amplifier of about 30% of its output power. The cord was rated for 10 amps, and the draw was about 6 amps. This measurement was done with a simple 3 1/2 digit Digital Voltmeter."

How about we all relax and drop this useless back and forth griping? That is my plan :-
RG

My personal quest is to find power cords that look inconspicuous hanging from the power outlets and running along the floor moldings. ;-)
RG

No need to make that rock any harder than it is to roll uphill. 👍

nonoise   ;-)
https://imgs.xkcd.com/comics/duty_calls.png
RG