Power Cords

[RayDunzl]

This has been brought up again (elsewhere).

http://www.shunyata.com/index.php/support/technical-articles/128-dtcd/308-dtcd-tech

It provides some comparisons of cable of different gauge under somewhat extreme conditions.

No mention of noise or shielding, just extreme current delivery.

At least they are showing a measurement of something...

Featuring the DTCD™ (Dynamic Transient Current Delivery) Analyzer

"the first and only power analyzer designed specifically to measure the differences between AC power cables, wires and connections."

 

[Blumlein 88]

Yes, mostly they show that with more wire gage for super short extreme current you get more current quicker. Really extreme current.

Roughly 30 volts applied for 230 amps with the venom and 130 amps with the base cable. .022 ohm vs .12 ohm approximately for the wire. So the good wire is for a short time absorbing 1150 watts of power while the bad wire is absorbing 1950 watts. Makes you wonder about when this would be really pertinent for home audio power cables.

 

[March Audio]

yeah, seen this previously.

They seem to have missed the concept/effect of power supply filter/reservoir capacitors........but have demonstrated the effect of ohms law and inductive reactance.

...wankers....sadly again its taking advantage of the uninformed HiFi punter. They have demonstrated some of the most basic electrical theory and implied it is of actual benefit within the context of a hifi system

 

[RayDunzl]

I suppose you're equally unimpressed by this rise time on the Black Mamba?

 

[Blumlein 88]

I suppose you're equally unimpressed by this rise time on the Black Mamba?

Well you caught me at a bad time. I was listening to Stevie Ray Vaughan. And it was so good, without a Black Mamba......well yes I was unimpressed by the graph. SRV was much more impressive. Damn I hope my neighbors aren't upset when I crank it to eleven late at night. I guess a Mamba would only make it worse. My class D power amps aren't that selfish with current and power anyway though they are quite powerful.

 

[March Audio]

I suppose you're equally unimpressed by this rise time on the Black Mamba?

It has lower inductance and resistance. None of which were an issue with the standard mains cable.

Oh and they didn't need to invent a special piece of test equipment to find any of this out. Why they didn't just use an off the shelf LCR meter I have no idea, I suppose it just doesn't have the same marketing cache.

 

[Speedskater]

Power lines are 50/60 Hz AC. All the useful power is below 500/600 Hz (OK, some might say it's 5000/6000). Component power supply circuit designers add RC snubber networks to limit PS high frequency response. Many audiophiles purchase power conditioners to limit high frequency response. These are all opposite of the Shunyata products.
In any case AC power is a series circuit. It starts at the power company transformer and ends at your component's transformer. So 6 feet out of maybe 600 feet won't increase high frequency response, even if we wanted to (which we don't).

 

[Speedskater]

........................................
Oh and they didn't need to invent a special piece of test equipment to find any of this out. Why they didn't just use an off the shelf LCR meter I have no idea, I suppose it just doesn't have the same marketing cache.

It must have been a challenge to design the DTCD test unit. It's not easy to dump that much current that quickly. But it has nothing to do with real world AC power. Early on they said that they were going to test other sections of a home's AC power system, But that never happened.

 

[March Audio]

As you said above its totally irrelevant what the last few feet of cable are doing in this respect because the impedance of the supply is governed by the entire cicuit back to the local transformer.

I suspect they didnt continue to do any further tests because they suddenly realised they had no idea what they were doing

 

[Thomas savage]

As you said above its totally irrelevant what the last few feet of cable are doing in this resoect because the impedance of the supply is governed by the cicuit back to the local transformer.

What if you were to run off a in house isolation transformer?

 

[March Audio]

What if you were to run off a in house isolation transformer?

Probably even higher impedance. Its irrelevant anyway because its the power supply inside the equipment which matters if we are talking about dynamic current capability.

Think about it. Where does the power come from when the mains ac cycle is at zero volts?

 

[DonH56]

^^^ Still limited by the primary side's current source capability, plus now you've added the transformer, which probably would be rather unhappy trying to deal with hundreds of Amperes in tens of microseconds...

I have a multi-thousand dollar 40 GHz cable hooked up to my 'scope and can readily prove it has much greater bandwidth than the cable connecting my audio processor to my amplifier. Not really feeling the need to buy a bunch of them for my stereo, however, despite their clearly measurable superiority.

 

[FrantzM]

Hi

Was about to write that in another thread but decided to drop the issue as it would not make a iota of a difference. I am almost resigned to the fact that many in High End Audio have taken some things to the level of religion. Nothing will change their faith. It continues however to astonish me that some are so willing to pay such prices for such wares. This truly should be studied, it may provide some insights in human behavior.

 

[tomelex]

This is a good topic for us. To me, a power cord is essentially explained with resistance, capacitance and inductance, connections, and understanding that when current flows fields are created. And, you can manipulate these things by varying these constants, you can twist the conductors, you can balance them to the ground wire and you can shield and terminate the shield at either end, etc. All these things affect the utility of the power cord.

About the only main issue with power cords is keeping them at right angles to your other cords or at distances from other interconnects etc, because they will produce fields, the larger the current through the cord, the larger and stronger the fields, and fields induce disturbance into other cables around them.

So, there is some art and design involved, but there is no magic there and certainly no correlation with the audiophool bait that is out there these days.

All above posts are right on the money.

 

[tomelex]

Hi

Was about to write that in another thread but decided to drop the issue as it would not make a iota of a difference. I am almost resigned to the fact that many in High End Audio have taken some things to the level of religion. Nothing will change their faith. It continues however to astonish me that some are so willing to pay such prices for such wares. This truly should be studied, it may provide some insights in human behavior.

Yep, well, I think it is because most audiophiles are not trained in electronics so what they read can make sense to them, and everyone knows that the more money you spend on something the better it is.......

 

[RayDunzl]

Obviously you guys haven't listened to them in your system.

 

[FrantzM]

The money thing and the absence of objective metrics are at the heart of the discussion. This Gray area is what sustain the High End Audio as a luxury market. It is used by many ...a few drops of scientific terms like : Quantum and nano...
It doesn't help that many audiophiles have the disposable income to indulge in their fantasies. What those-who-can, disburse for a PC doesnt challenge their financial wellbeing. OTOH it increases their standing and the width of their soundstage ... What's not to like and defend?

 

[RayDunzl]

Meanwhile, what caught my eye when I first saw the DTCD stuff, after eyeballing the huge test currents, was this:

The 'real world' consideration led me to think about diodes (rectification) and transformers (step-down would be typical)...

My imagination on this:

During the AC cycle the voltage applied to the transformer rises, and at some point the voltage produced at the secondary begins to rise above the stored voltage in the filter capacitor, and begins to forward bias the diode in the rectifier, which begins to permit current to flow into the filter cap.

Not a huge on/off current dump pulse. but a slowly (at the microsecond time frame) increasing forward bias on the diode, that raises the voltage in the cap, that reduces the forward bias on the diode, which throttles the current flow into the capacitor.

The greater the step-down ratio of the transformer the less abruptly the voltage rises in the secondary, slowing the turn on of the rectifier diode even more.

Rendering the fabulous pulse carrying capability of the Black Mamba moot.

I could probably fool around with a sin table and figure out the voltage change per microsecond for the degrees in the AC cycle of interest... but it would be a bit fumbly.

Maybe someone here has the tools and could simulate a simple power cord/transformer/rectifier/capacitor/load just to put some numbers on what 'really' goes on.

 

[Sal1950]

About the only main issue with power cords is keeping them at right angles to your other cords or at distances from other interconnects etc, because they will produce fields, the larger the current through the cord, the larger and stronger the fields, and fields induce disturbance into other cables around them.

+1
I'm not sure how important it is in absolute terms, but I was taught this decades ago and still practice the same wire routing strategies to this day. I've gotten criticized for my cable management as I don't bundle everything neatly into one big loom and have lots of stuff visible. Get's a bit messy then in a big mch rig, Shame on me I guess.

 

[RayDunzl]

My cables are a six year tangle.

No ill effects noted, by ear or sonic measurement.

No pride in this, just another data point.

Wow... That's 18 months ago... It's worse now...