15A vs. 20A power cord questions


I'm installing dedicated 20A lines with 10AWG cable and Furutech GTX-D 20A wall receptacles. I am currently using the standard IEC power cords that came with my Rogue Cronus Magnum and VPI Scout 1.1. 

I rather not upgrade the power cables at this time. I would like to see the effect the dedicated lines and outlets have first. Are there any issues with running 15A power cords into a 20A outlet and line? Would a 20A power cord possibly sound better or is it just a matter of the blade orientation?
asp307

I am an easily confused old man.

My Atma-Sphere MA-1 140 watt tube amps use 5 amp fuses.

When I look at these fuses, the wire connecting one end to the other is absolutely tiny. At my age I need reading glasses to see it. Yes it is that thin.

This is the conduit through which the electricity flows. All the electricity.

The question I have: do you have an isolated ground with this dedicated 20amp service?.

This involves running a new wire outside, connected to a new copper rod, and having that rod driven into the ground, deep.

LOL, there is a lot more to many aftermarket power cords than merely the size of the conductors used. Nothing posted thus far has addressed any of that.


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Here is a quote from a post from Ralph, of Atma-Sphere:


"With power cords its all about voltage drop across the cord. Some of that is at 60Hz, and some of that is much much higher- well above 30KHz-100KHz depending on the power supply in the unit with which it is being used.

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.

The more insidious problem is high frequency bandwidth. The power supplies of most amplifiers have a power transformer, a set of rectifiers, and a set of filter capacitors. The rectifiers only conduct when the power transformer output is higher than that of the filter caps. So:

When the caps are fully charged the amp is able to play. As it does so, the caps are discharged until the AC line voltage waveform gets high enough again that the rectifiers in the power supply are able to conduct. Depending on the state of charge of the filter capacitors, this might only be for a few microseconds or it might be a few milliseconds. Either way, the charge is a spike which has very steep sides- and requires some bandwidth to make it happen.

If the power cord has poor high frequency response, it will current limit on these spikes. This can result is subtle modulations in the power supply or even a sagging power supply voltage.

Romex wiring found in many buildings actually works quite well. So it really becomes all about that last few feet and also how well the power cord is terminated- molded cords generally are not terminated very well. If the ends of your power cord get warm after a while, you know you have a problem!

This can be measured, its quantifiable and also audible as many audiophiles know. Anyone who tells you differently probably has not bothered to do any measurements- please refer them to this post.

I can go into more depth but this is it in a nutshell. Incidentally, Shunyata Research is refining an instrument that does a more in-depth analysis of what this is all about. At the link you will see that their tests essentially confirm what I have said here."
http://www.theaudiobeat.com/visits/shunyata_visit_interview.htm

End of quoted material.

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Agon thread Link:
https://forum.audiogon.com/discussions/audiphile-power-cords#41


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As for the use of an isolated earth ground rod, that’s a no, no.

The purpose of the safety equipment ground is to provide a low resistive path for ground fault current to return to the source. Mother earth is not a low resistive path. If the earth is used as a path for ground fault current, and there is a ground fault event, the area around the earth driven ground rod works great for hunting fish worms.

The earth does not possess some magical mystical power that sucks nasties from an audio system.

jea48:

Power cords with 5-15 plugs to IEC320-C19 connectors and 14/3 conductors are very common, so an equipment mfr can easily bundle one if he chooses to put a C20 receptacle on his cdp for mechanical coupling reasons. But, like you said, if someone decides that he can use this cord to substitute for his lost Krell FPB 600 power cord, then yes it would be a potential problem (maybe that it's why most mfrs don't do it). If it was me, I would put a fixed power cord with a 5-20 plug on amps I manufacture that can draw more than 12-amps. Heck, you don't see air conditioner or microwave oven manufacturers making easy to mistakenly plug their stuff into the wrong outlet. 

Hi gs5556,

Glad to see you posting again.

Most manufactures of audio equipment want and need to use a 15 amp plug to feed their equipment. As you know the majority of the convenience outlet branch circuits in homes are 15 amp, using #14awg copper wire. Only a 15 amp receptacle can be installed, connected, to a 15 amp branch circuit.

Audio Manufactures wouldn’t sell much equipment if they used a 20 amp male plug. So they need the 15 amp plug if they are going to sell audio equipment to home consumers in the US and Canada.

I think the problem with some manufactures, that build big amps, isn’t that their equipment draws more than 12 continuous amps. That’s a lot of amps for an amplifier in a home. 12 amps X 120Vac = 1440 VA, watts.

The problem is some manufactures are too tight to install a soft start circuit for powering up the amp. Without a soft start circuit the full inrush current trips the 15 amp branch circuit breaker at the electrical panel. And the bad thing, the manufacture probably knows it’s going to happen.

Sometimes in the owner manual it might say the amp should be fed from a 20 amp dedicated circuit. And that is the manufacture’s way out. In some cases even a standard 20 amp breaker will trip due to inrush current.

Jim




asp307 said:
Regarding a twisted pair or standard cable to link the breaker to the outlet, any advantages or is it all about the grounding?

ASp307,

It would help if you said what country you live in. I assume it is a country that has 120V power. The reason I say that is because of the type of receptacle you said you were using in your OP.

Here is some reading material for you. Read pages 15 through 36.

http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

Jim

@jea48 I live in Pittsburgh, PA. This was pretty informative; thanks. It was recommended to me by a US producer of speakers/cables to ground to the earth using rods and to use a twisted pair for the connection between the breaker and the outlet. These slides seem to debunk this...