I Believe in Power Cords

[DonH50]

Don-The main reason I wrote the positive statement that I do believe in power cords is the fact that with the new power cord, the racket my huge power transformer use to make is gone. Krell recommends having a dedicated 20A outlet for the KSA-250 and I do. I was feeding the Krell with a wimpy, er, I mean an excellent up to the task 12-14 gauge power cord. When I installed the new 7 gauge power cord-boom, the noise is gone. Now is that because the new power cord is very well shielded or is it because it can draw much more current from the wall due to it being 7 gauge or is it a combination of both? I really don't think the transformer mechanical noise is going to go away due to "wiper action" of removing and installing a new power cord.

Hi Mark,

I want to be clear that I am not questioning your results; I am curious and thus speculating about the cause. As I said, I have seen benefits with power cord changes, but rarely. I like the idea that there was a very obvious benefit in your case. Treat my posts on the subject as the idle musings of an old fart.

If there was oxidation causing poor contact at the either end then it could explain this. If there were some sort of interfering signal that the new power cord is filtering that could also be a factor. If the previous cable was defective or had a poor ground, that could explain it (in the past I have run across more defective cords than I would have imagined, very often a bad connection on the ground or neutral so it wsa not obvious the cable was defective). A standard 20-A line means 12 AWG cable to the receptacle, at least in CO, so I am skeptical the increased gauge mattered, assuming you plugged it straight into the wall. I do not question your results, I am just musing out loud about what might have caused them. A cord that eliminates power transformer hum is an interesting challenge. Transformer hum can be caused by unbalanced lines, poor grounding, or (severe) RFI, among other things; a new power cord replacing a defective cord could solve the first two, and if it included filtering would help the latter.

Curious: Do some power cords include in-line (series) capacitors to block DC offsets on the line? A DC offset could certainly cause the transformer to buzz.

I suppose a stretch idea would be moving the amp whilst installing the chord changed the way the transformer was sitting so it is better isolated (e.g. hung up on a mounting bolt so the little isolation bumpers did not work and moving it freed the mount) or dislodged a wayward component that was pressed against the transformer...

No worries, just curiosity and idle speculation - Don

 

[garylkoh]

Hello, Gary. This, I would be interested in learning more about [I have Class A/B]. BTW, IMO there is nothing to "believe". They can and do make a difference. This is almost always situation dependent IME and for those that can't hear any difference, your wallet thanks you. I'm sure my wallet has some harsh words for me but at least my ears are thanking me.

Tom

It's proprietary info, but my take on this is that it is all about the way the power supply of the component interfaces. There is nothing much you can do about the lousy power (except with power conditioners, and then the results are again variable) or the miles of bad cables coming from the nearest pole pig.

Different type of components require different treatment. A Class A power amplifier for example has a low delta in the current draw when operating. The draw is almost exactly constant. This is the same with a preamp or a DAC. A turntable or a tape deck has a motor. Most are DC servo motors. Motor drives need a different treatment as this can be "choppy" depending on how the current is drawn. A Class AB power amp has a low standing current, and then the current draw tracks the energy in the music (buffered by the power supply) and requires a third way different to treat the interface.

 

[garylkoh]

Curious: Do some power cords include in-line (series) capacitors to block DC offsets on the line? A DC offset could certainly cause the transformer to buzz.

One of the most common reasons for transformer buzzing is due to core saturation with DC offset in the power line. The DC impedance of most transformers are very low. If the power cord has significant DC impedance, distributing the impedance between the power cord and the transformer may be sufficient to reduce the DC enough that the transformer stops humming.

 

[microstrip]

I am in the Frantz camp on this issue. That said, I can't afford this experiment to work in my system as I have sold around 15 or 20 very expensive power cords over the last 18 month (to pay for other gear) as I NEVER heard any difference, even sighted. I tried blind and of course I failed that as well.

So I will pass on this experiment

And if you remove your current power cords and replace them with the cheapest type of computer PC cords costing about $2? Do you perceive any difference?

 

[microstrip]

One of the most common reasons for transformer buzzing is due to core saturation with DC offset in the power line. The DC impedance of most transformers are very low. If the power cord has significant DC impedance, distributing the impedance between the power cord and the transformer may be sufficient to reduce the DC enough that the transformer stops humming.

Gary,
I though about it, but Mep reports the opposite - lower hum with much thicker (lower resistance) cable.

 

[flez007]

I have found more impact or changes in my system swapping AC cables than IC ones, not only in noise floor as Mark mentioned, but also on dynamics and bass resolution.

 

[garylkoh]

Gary,
I though about it, but Mep reports the opposite - lower hum with much thicker (lower resistance) cable.

That is why I say DC impedance. If there is a lot of capacitance in the cable, DC impedance might be high.

 

[mep]

I doubt there is oxidation on a brand new power cord so I don't think that would explain it. If the cable was defective, I doubt it would work at all. I can always ohm out the positive and neutral wires as well as the ground to make sure they are fine though. If the amp hummed through the speakers with the old power cord, it would be a different problem. There was no hum through the speakers with the power cord that Krell sent me to use with the KSA-250. Just the transformer was making some noise when you got up close to the amp.

 

[microstrip]

I doubt there is oxidation on a brand new power cord so I don't think that would explain it. If the cable was defective, I doubt it would work at all. I can always ohm out the positive and neutral wires as well as the ground to make sure they are fine though. If the amp hummed through the speakers with the old power cord, it would be a different problem. There was no hum through the speakers with the power cord that Krell sent me to use with the KSA-250. Just the transformer was making some noise when you got up close to the amp.

Does it still hum if you use any cheap 15A cable you have at home?

 

[Johnny Vinyl]

I've not heard a detrimental effect with aftermarket PCs. You may also want to look at Shunyata Research lower priced cords. Bob Grossman likes them.

Ah Shunyata...I knew I was missing one!

I've heard all good things (excellent performance/value ratio) about Shunyata power cords and all.

Yes, I believe their entry-level PC got pretty high praise.

Thanks guys!

 

[mep]

Does it still hum if you use any cheap 15A cable you have at home?

Honestly, I don't know. Now that I have bought a new PC and the Krell is working the best it ever has, I'm loathe to *break* it and try other rot gut cords laying around my work space in the bin of abandoned cables.

 

[FrantzM]

Can you tell us what is the exact model of double conversion APC you are using? I have several at work and may be one is similar to yours and I can try it. My experience is different from yours - I have used PS Audio power regenerators and an ExactPower active corrector - both generate technically perfect mains and power cables still made a large difference.

microstrip

APC Surta3000 VA. Bought used for my IT business it was to keep some server running. We moved to a much co-location facility with all the bells and whistles (Cooling, DC power, online and mobile reports, configuration and alrms, etc) and no longer needed it. Noisy though. I happen to have the garage next to the living room so ... Very clean output. There are several other from APC, Liebert, Tripp-Lite, .. the usual suspects. Make sure these are online double conversion and not line interactive.
The PS Audio Power Regenerator is rated, I believe at 1200 VA, assuming a 0.8 power factor for the connected components (it can be less) that leaves you with about 900~950 Watts.. maybe less, that is not enough for a Class A 200 Watts amp ... I believe it would work on source components, these usually don't draw much power. The Surta will deliver up to 2100 watts with less than 5% of THD and +- 5% of voltage regulation .. Second hand about $1000 .. less than many audiophiles Power cords and even some power strips ... There are on eBay some 6 KVa models at less than $2000 ... the THD is even less with the higher power models and regulation tighter they are 208/240. Their installation is not a job for the casual audiophile unless he/she knows his/her way around power electricity and electrical regulations ...

Didn't want to hijack the thread. I answered a specific question .. back to the Power cords discussion ...

 

[DonH50]

I doubt there is oxidation on a brand new power cord so I don't think that would explain it. If the cable was defective, I doubt it would work at all. I can always ohm out the positive and neutral wires as well as the ground to make sure they are fine though. If the amp hummed through the speakers with the old power cord, it would be a different problem. There was no hum through the speakers with the power cord that Krell sent me to use with the KSA-250. Just the transformer was making some noise when you got up close to the amp.

No, I was thinking of oxidation on the old power cord or receptacle (wall and/or amp). Pulling the cord out and plugging in a new (or the old) one would provide a "wiping" action that cuts through the oxidation to make a better connection. Frankly, I doubt that is the cause of the hum.

I have seen several cases where the power cord made a bad connection or even had open wires and still worked, for instance with an open or very high-impedance (relative, few ohms vs. <1 ohm) ground wire, or even with the neutral open and the return path through the safety ground. Again, throwing out thoughts, not saying that's true in your specific case.

It would be interesting to rn some experiments, but I strongly suspect you have little inclination and time for that now that everything is up and running! There are some things I would like to piddle with in my system, but a walk down and look at the hundreds of pounds of stuff I'd have to move is a good deterrent for me...

@Gary -- A 7 AWG cord would have much lower resistance than a 12 AWG, though in either case I would think DCR would be insignificant for a good cord. I would not expect a new cord's lower DCR to reduce the impact of DC on the line; the opposite, in fact. What I have seen are marginal cables, sometimes just bad connections, that unbalance the return current and cause an effective offset. It is also possible the old cord was bad, not bad enough to not work, but with high enough impedance on one line (e.g. sometimes a bad joint at the plug so only a few strands carry the load) to induce some sort of offset relative to ground.

That (DC on the line) is why I asked about caps in the cords... I know some conditioners include AC coupling caps but they need to be serious beasts to handle high AC currents.

I don't know what's really going on, but it is an interesting problem.

Meanwhile, snowing again, my back aches thinking about having to get out the snowthrower and shovel again tonight...

 

[microstrip]

(...) I don't know what's really going on, but it is an interesting problem.

Meanwhile, snowing again, my back aches thinking about having to get out the snowthrower and shovel again tonight...

Don,

IMHO unless we persuade Mep to take a few experiments it is not possible to get a plausible explanation.

But if your snowthrower is electrical may be you can try listening to its noise with different gauge power cables.

 

[mep]

What experiments do you have in mind?

 

[microstrip]

What experiments do you have in mind?

Just putting another inexpensive decent quality AWG 12 power cable again and listening if the mechanical hum returns.

 

[Phelonious Ponk]

Hello, Don. Generally speaking, I can not argue. Perhaps it's what you had mentioned above, I'm the last one to verify or prove this to be true. One test I have always invited folks to try if they are on the fence as to what hits your ears [measurements aside] goes as follows;



While this may have nothing to do with the imaging and sound staging characteristics [or many other characteristics for that matter], I have found over the years that this is a great basic test to see if a power cord can make a change for the better in someone's rig that utilizes all stock power cords and allows for the diehard PC "can't make a difference" person to hear what they never thought possible before. The reviews vary but for those who have tried, their audio journey can continue without reservation or self-imposed limits.

Tom

If you believe you are immune to expectation bias, this works. If you understand the reality of expectation bias, you'll know that you'll most likely hear what you want to hear.

Tim

 

[mep]

No, I was thinking of oxidation on the old power cord or receptacle (wall and/or amp). Pulling the cord out and plugging in a new (or the old) one would provide a "wiping" action that cuts through the oxidation to make a better connection. Frankly, I doubt that is the cause of the hum.

Don-My 20 amp outlet is basically brand new. I had it installed when I bought the KSA-250 so I doubt there should be oxidation on the receptacle. The power cord that Krell sent me was brand new as well. I think we need to look elsewhere.

Sorry about all of your snow.

 

[Shaffer]

Even though I build cords as a hobby of sorts, I'm not a full believer. I've had all kins of cords in my system(s) and mostly struggled to hear any difference at all. Once in a great while, however, I really do feel like I hear something, and once, quite recently, I heard a very significant change for the better with a particular design. I ordered parts to make a few more and outfit the whole system. We'll see how things turn out.

This being said, ultimately, I don't really care if cords make a real difference or not. If they let me enjoy my system more, that's all that counts.

 

[DonH50]

Don-My 20 amp outlet is basically brand new. I had it installed when I bought the KSA-250 so I doubt there should be oxidation on the receptacle. The power cord that Krell sent me was brand new as well. I think we need to look elsewhere.

Sorry about all of your snow.

Yeah, like I said I really don't think that is it.

As for the snow, well, that's one reason I live here. It's pretty, so long as I don't have to drive in it or clear it. And we've been low this yearand the past few; seem to be making up for it. It also has my wife in trouble -- she's visiting her mom in MO and has been caught in the blizzards there (that were ours a day ago). Two in less than five days, yippee. I figure it's 50-50 she can make her flight tomorrow... Bad news is it all hit west of the airport so flights are OK, thus changing her ticket is going to be costly.

@microstrip -- The snow thrower is gas powered. I would be a little nervous running a snow thrower with a cord plugged into the house. Snow/water and fast moving parts don't often play well with long power cords...