Power cords, a trip into the unknown!

[j_n]

We prefer 800 x 600

Ah, thanks. So that means amirm won't post a honkin haversine plot that's three times wider than my monitor??

Cheers, john

 

[amirm]

Ah, thanks. So that means amirm won't post a honkin haversine plot that's three times wider than my monitor??

Cheers, john

You need a new monitor. That was my desktop shrunk by one level already . I am always mindful of people with poor eyesight.

PS for those not following the inside joke, it was a graph I posted elsewhere.

 

[DonH50]

Ah, thanks. So that means amirm won't post a honkin haversine plot that's three times wider than my monitor??

Cheers, john

Ah, sorry, no it does not mean that...

 

[j_n]

Ah, sorry, no it does not mean that...

I didn't think so...

Hey there Don, how are you? Been a while.

Ya know, one of these days we're gonna hafta have a reeeal long discussion about T-line theory..

Not today, but eventually...

Today....today is about EMC...

Cheers, John

 

[fas42]

I do believe that it is possible that the design of the connectors inside the plug ( prong or iec) may have something to do with the performance. This would make some sense as the connection at the plug to the wire could induce losses. One interesting thought, which I think Frank may have touched upon in another thread, is to solder the wires directly to the component in question. Thereby, doing away with any potential loss due to the plug. I did not do this so I have no basis in this regard.

An excellent path to follow, Davey. Unfortunately, very unfortunately, every just straight physical contact is a weakness, so if you solder it would be an excellent move. The very first thing I start doing 25 years ago was to bypass every metal pushed onto metal contact with a soldered link, and that allowed me to make major progress.

The simple reason is that metal to metal contact starts corroding the instant after it's made, starts developing nasty diodic characteristics, which are absolutely great for rectifying high frequency rubbish in the air and coming down the copper. Very subtle, but adds that unpleasant grunge that so much hifi has ...

Frank

 

[fas42]

For those who want to explore the value of soldering elements of the system together, the key thing to evaluate is the quality of the treble. I've always relied on the tonal quality of a cymbal crash, the hi hats; try a recording where the cymbal sound is just okay, not brilliant but not terrible also. Try focusing on the shimmer of that cymbal, with normal versus soldered connection, and all going well one way of doing things should stand out. And with the normal connection, give the pushed together link time to "stabilise", 10 minutes or so, before you pass judgement ...

Frank

 

[garylkoh]

I wish power cords didn't make a difference too, but unfortunately they do. I have the task of swallowing my words because for years I used to tell my customers NOT to use expensive power cords for the amplifiers on my speakers and my tube amps and just to use the black cord I supplied.

I had started a thread on power cables a year ago... interesting read, for sure. My opinion hasn't changed - assuming the right gauge for each application, they can affect impedance between the component and the wall (i.e. how fast they can deliver impulse current), and they can affect noise (both in the power line and as potentially radiated by the cord around it).

Unlike signal cables, the requirement for a power cord for a piece of audio equipment is totally counter intuitive. For one, there is no impulse current requirement - unless an amplifier is directly connected to the IEC inlet. There is always a capacitor bank that will supply the sudden draws of current that music requires. Then, between the capacitor bank and the IEC inlet, there is usually a large transformer. These two will filter the impulse (or anything remotely music-related) from the input requirements.

For a piece of audio equipment, unless there is something really extraordinary like a 100,000W pro-sound amplifier, the current draw is minuscule. Class A amps, tube amps, might require a more steady draw but even there, I have not been able to detect anything related to the music waveform in the input requirement.

There IS a requirement for the design of a power cord for audio, but it goes against anything we have known. What it is, I am not prepared to say.

 

[fas42]

For one, there is no impulse current requirement - unless an amplifier is directly connected to the IEC inlet. There is always a capacitor bank that will supply the sudden draws of current that music requires. Then, between the capacitor bank and the IEC inlet, there is usually a large transformer. These two will filter the impulse (or anything remotely music-related) from the input requirements.

You hope, Gary, you hope. Sorry, it's not that easy: if you actually go through a proper exercise of simulating what happens in an ordinary power supply, you discover it's a bit of a disaster. That lovely DC voltage is very susceptible to being affected by what happens on the main's side; and, likewise, what the amplifier does to the mains voltage is very nasty indeed. That big Krell is giving your household circuitry a very unpleasant time ...

So, like it or not, your whole house electrical system is part of the audio circuitry, no matter how much you would wish it to be otherwise ...

Frank

 

[garylkoh]

And you've hooked up an oscilloscope to the capacitor bank and seen the voltage on the bank vary with the music waveform? Pray tell how does a big Krell with a linear power supply give the household circuitry an unpleasant time. I do acknowledge that a switching power supply will, but a linear power supply?

 

[fas42]

And you've hooked up an oscilloscope to the capacitor bank and seen the voltage on the bank vary with the music waveform? Pray tell how does a big Krell with a linear power supply give the household circuitry an unpleasant time. I do acknowledge that a switching power supply will, but a linear power supply?

Even better. I've used the voltage of the DC supply to drive another amplifier, a "perfect" voltage source becomes just another input to an audio system. And very eye opening it is too: as I've said before, could be a great backing track to some hip hop, or techno music ...

If the Krell is doing some heavy bass driving, its great claim to fame, then at the peak of the mains voltage peak it will draw a very sharp current spike from the household supply, 10's of amps, with very savage high frequency content. This ripples through the household wiring, injecting glitches into all the equipment plugged in: most of the time this will be irrelevant to the appliance, but it may upset the CD player or music server somewhat ...

Frank

 

[garylkoh]

Even better. I've used the voltage of the DC supply to drive another amplifier, a "perfect" voltage source becomes just another input to an audio system. And very eye opening it is too: as I've said before, could be a great backing track to some hip hop, or techno music ...

I guess we'll have to differ here. I didn't see voltage fluctuations on an oscilloscope in a couple of tests I did, but I guess you can hear what I can't see.

 

[Orb]

Gary,
one aspect I never really seen mentioned is that of voltage sag when the amp is working harder.
Always wondered if this trait can be influenced by the realworld power cables (not theoritical spec ones that do not exist before anyone gives an example).
Cheers
Orb

 

[FrantzM]

Gary,
one aspect I never really seen mentioned is that of voltage sag when the amp is working harder.
Always wondered if this trait can be influenced by the realworld power cables (not theoritical spec ones that do not exist before anyone gives an example).
Cheers
Orb

Try as much as I may I can't begin to see how a competent (of sufficient gauge to carry all the amperage the DUT will ever need) power cord could contribute to voltage sag ....

Power Cord discussions are to me the epitome of our audiophile obsessions... We conclude they make a difference based on difficult to substantiate or replicate observations .... Then we go fishing for morsels of 'science' which would correlate to the (suspects) observations.. It should noted also that Science is rejected in the very same discussions and often by those who invoked it.

 

[Orb]

Frantz,
I did not say contribute to the actual sag, but mean once it starts to happen do real world mains cables influence any factors, and maybe how the sag behaves.
As I said, I prefer to keep engineering theory out of this, which again is something I am familiar with, and as you should note I am one of the most often posters with aspects of actual scientific facts and papers.
I would not mind Frantz but is frustrating when comes out with a generic comment about "science" and how it is rejected by audiophiles, when there are contributors to audio magazines actually have classical science degrees (masters/phd level) and even research lab experience - which I feel quite a few ignore when dissing them or even subjects those contributors touch on (appreciate this is broadening the scope beyond what you just said but it is part of the symptom of criticising audio and anyone wanting to discuss aspects others do not like).
The generic bashing really should stop IMO.

Cheers
Orb

 

[FrantzM]

Orb

I wasn't meant to be a bashing. if it was construed or interpreted as such , i apologize. I do however think that at times we need to face the facts that observations need to be more carefully conducted to conclude with the confidence we tend to infuse in many a discussion about audiophile items.
I would also add that you , Orb, make sure to remain level and centered. You references are almost always educative and I commend you for the quality of your research and the enthusiasm you display when it comes to the seach for better reproduced music in our homes. Mine is waning , seeing the industry simply becoming a Luxury one, things beceom more expensive by the day where in ALL other technological endeavore the contrary is the norm. While the cost to produce better products decreases the price of such gears, aside fro a few exceptions steadily rises too often to ludicrous level and frankly I am bothered by that ... Opening any of these Power Cords will show to any person with the inclination to investigate that they are simply a beautiful sheath with common wires and an oversize terminals (Plug and IEC sides) .. Measurements from these PC shows close to nothing and frankly their purpose is to pass current at a single frequency , one of the simplest task that an interconnect will ever have to do ... It is also too consistent that with out the knowledge of these PCs in the chain observations are closer to pure chnace than anything this side of tossing a coin ..
l am not accusing the whole audiophile community of rejecting science but if I were to just gleam around here in the WBF, the tendency to reject science is patent. Many (not all) do proclaim that some phenomenon can heard but cannot ever be measured so what to make of that?
There was no intent to bash but there was an intent to wonder about the validity of our conclusions about PCs.

 

[garylkoh]

Gary,
one aspect I never really seen mentioned is that of voltage sag when the amp is working harder.
Always wondered if this trait can be influenced by the realworld power cables (not theoritical spec ones that do not exist before anyone gives an example).
Cheers
Orb

Orb, I haven't seen that - no matter how hard an amplifier is working in the audiophile context. Even the biggest loudspeakers are only drawing fractions of an amp. The time constant of a large capacitor bank slows down the requirement from the other side of the capacitor bank (at the IEC) to such that I couldn't see the difference on an oscilloscope. The larger amplifiers have an even larger capacitor bank, and hence even less chance of any voltage sag.

Audiophiles are sometimes obsessed with the dimming of the lights when a large power amp is first plugged in and turned on. This initial surge powers up the transformer and the capacitor bank, and then it just hums along with a constant current draw.

 

[garylkoh]

Try as much as I may I can't begin to see how a competent (of sufficient gauge to carry all the amperage the DUT will ever need) power cord could contribute to voltage sag ....

Power Cord discussions are to me the epitome of our audiophile obsessions... We conclude they make a difference based on difficult to substantiate or replicate observations .... Then we go fishing for morsels of 'science' which would correlate to the (suspects) observations.. It should noted also that Science is rejected in the very same discussions and often by those who invoked it.

Frantz,

May be it's an obsession, but if I can hear a difference, I do try to find some scientific basis behind it, and we try to objectively discuss it here. That's what's best about What's Best Forum. Like in the discussion about loudspeaker cables, in all our simulations, we couldn't discover why we can hear a difference. There has to be some other explanation, but at least we have been able to conclusively discount some. That's the nature of science. Without being exhaustive, we are no better than just guessing.

I have never said that a phenomenon can be heard but never measured. I say that I still don't know how to measure it - and I am open to finding new ways to measure.

 

[garylkoh]

Gary,
one aspect I never really seen mentioned is that of voltage sag when the amp is working harder.
Always wondered if this trait can be influenced by the realworld power cables (not theoritical spec ones that do not exist before anyone gives an example).
Cheers
Orb

Oh, by the way, running at high power into a resistor, you will see something - especially a Class D amplifier with a switched mode power supply. These do not have much of a capacitor buffer. However, I have not been able to measure any voltage fluctuations when running at normal listening levels into a loudspeaker.

 

[microstrip]

(...) l am not accusing the whole audiophile community of rejecting science but if I were to just gleam around here in the WBF, the tendency to reject science is patent. Many (not all) do proclaim that some phenomenon can heard but cannot ever be measured so what to make of that?
There was no intent to bash but there was an intent to wonder about the validity of our conclusions about PCs.

Frantz,
I would say the opposite - most scientists (not the whole science surely) have rejected the audiophile community, as they could not explain what is heard. Just consider the case of amplifiers. Most developers and manufacturers with scientific programs will suggest us that their amplifiers sound better than the competition. But they will never explain us how they correlate the sound qualities of their amplifiers with technical features - at most they will enter the neutrality game, just claiming they are more neutral than any other.

 

[DonH50]

A large part of the measurement problem falls into three general areas, I think:

1. Having the appropriate equipment (often very expensive);
2. Having the knowledge and experience to use the equipment in an appropriate way (may involve special fixturing etc.); and,
3. Knowing what to measure (including test conditions; e.g. a load resistor does not behave like a loudspeaker).

The latter is key (figuring out what to measure to identify a particular sound, or lack of) but no less so than the first two, imo. Any of us can point to obviously flawed tests, but I have certainly performed tests I felt were rigorous and still been surprised when later reality rose up and whupped me upside the head.