Power Cables

Sisyphus51 6-13-2018

Why do folks insist that "Power Cables" need to have a bandwidth equal to that of a very high-spec amplifier’s audio bandwidth? Are you people INSANE? We are talking about 60Hz AC here!

If your power cords are carrying Khz range signals or noise there is something horribly wrong with your amplifier that needs to be corrected immediately, if not sooner because you are essentially operating a Radio Transmitter in violation of Federal Law!

Not sure you are realizing that if current is only drawn during a small fraction of each 60 Hz cycle, as Ralph/Atmasphere clearly explained in the post I quoted, spectral components are present at vastly higher frequencies than 60 Hz.

Which, btw, is the main reason I said in my post earlier in the thread that:

Almarg 6-12-2018

Power amps can generate significant amounts of high frequency noise that can be fed back into the power cord and affect other parts of the system, to a greater or lesser degree depending on the shielding, bandwidth, capacitance and other characteristics of the power cord.

Sisyphus51 6-13-2018
I just measured the drop across the 5.5 foot original power cord on my 1964 Scott 222D Integrated Amp.....

Among a number of other vintage pieces I have an H. H. Scott 299C integrated, ca. 1961, that I sometimes use in a second system. 7591 power tubes and a 5AR4 rectifier. Very nice piece. I sometimes use it in conjunction with a 1952 Radiocraftsmen 10 mono AM/FM tuner, the combo producing very lush, rich, and beguiling sonics on FM.

Regards,
-- Al

I have to dispute the assertions of the article referenced by you in your post. Current is not drawn in pulses. That is what the rectifier and filter capacitors are for - to store enough charge for smooth operation. And if the charge in the power supply is sagging below full supply voltage it is because of excess power consumption or a failure in the power supply! 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. It certainly will not cause a two figure loss in power output! That is ludicrous!
If one desires increased dynamic range in their music reproduction, one needs 1. More Power. 2. More efficient loudspeakers. 3. Less sound absorption in the listening room.
Expensive power cords will not do the job!

Good Night!

sisyphus51

geoffkait
Re. Pop Quiz " How come HDMI cables are directional?"

They are not unless they have active circuitry built in to compensate for unusually long runs. ;-)

>>>>Quick, you better tell Audioquest! I have their Carbon HDMI Cable which, like all of their high end cables, HDMI cables and power cords, are controlled for directionality during the manufacturing process. Great picture btw. 😀 When only the best will do.

to whit,

”DIRECTIONALITY: All audio cables are directional. The correct direction is determined by listening to every batch of metal conductors used in every AudioQuest audio cable. All signal conductors controlled for digital-audio direction in AudioQuest HDMI cables, and care is even taken to run the conductors used in the Audio Return Channel in the opposite direction to ensure the best performance for that application. Arrows are clearly marked on the connectors to ensure superior sound quality.”

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