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Effects of power cords - Page 3  

post #31 of 56
Thread Starter 

Since we have some knowledgeable folks here, what I am really dying to know is why the last few feet of power cable matters, compared to the miles that comes before it. I believe it DOES matter,  a LOT, because I've heard good power cords (better ones than I can afford) where it was clear that the real potential of the component was coming out. But how can that be? 

 

Is it just reduction of RF? If that was the case, why wouldn't good power conditioning plug a garden-variety shielded PC be the complete solution?:

 

Mark

post #32 of 56
Quote:
Originally Posted by markheadphonium View Post
 

Since we have some knowledgeable folks here, what I am really dying to know is why the last few feet of power cable matters, compared to the miles that comes before it. I believe it DOES matter,  a LOT, because I've heard good power cords (better ones than I can afford) where it was clear that the real potential of the component was coming out. But how can that be? 

 

Is it just reduction of RF? If that was the case, why wouldn't good power conditioning plug a garden-variety shielded PC be the complete solution?:

 

Mark

 

Expectation bias. Do some kind of test and find out the horrible, horrible truth.

post #33 of 56
Quote:
Originally Posted by markheadphonium View Post

Since we have some knowledgeable folks here, what I am really dying to know is why the last few feet of power cable matters, compared to the miles that comes before it. I believe it DOES matter,  a LOT, because I've heard good power cords (better ones than I can afford) where it was clear that the real potential of the component was coming out. But how can that be? 

Is it just reduction of RF? If that was the case, why wouldn't good power conditioning plug a garden-variety shielded PC be the complete solution?:

Mark

One argument goes like this:
The last six feet matters because all your audio components probably all go into the same power bar, and all your components have six foot power cords.
In addition, (the argument goes) the biggest source of power line interference to your components are the other audio components themselves because they are all separated by 6 feet of cable. And if you have a TV and maybe a Blu Ray player and maybe a satellite or cable box hooked into your audio system then you have sources of RF.

OTOH, as you have pointed out:
You could try plugging everything into a good power line conditioner and use good shielded power cords.
Or if you are using specialized power cords, what's actually in the power cords that mitigates power line noise?
post #34 of 56
Quote:
Originally Posted by Chris J View Post

Brothers and Sisters,
Let us bow our heads and calculate...

Take a 6 ft. power cord with 10 pF/ft of capacitance and 0.155 uH of inductance. It may have a name like, um, Nordost Bue Heaven.
At 1 MHz this is XL = 5.84 Ohms and XC = 2653 Ohms.
Very interesting....

Yes, but if you read what I wrote above, I asked "how much will a power cord pass at 1GHz?" That's because I had to go up to 1GHz to get something resembling a short circuit for the given diode capacitance.

Quote:
The real thing to keep in mind is that HF noise still breaks thru a garden variety PSU if you do not take action to prevent conducted HF noise, i.e. board layout, lead dress, appropriate capacitors, etc.

Certainly.

Quote:
The noise doesn't break thru only when the rectifier diodes are switched on.

No, it doesn't. But the charging current to top off the reservoir capacitors does, which was the point I was making in my original post before I let myself get sidetracked with the RF issue.

Quote:
In fact, the rectifier diodes switching on and off are part of the problem.

Yes. And that will be the case even with "perfect" mains AC and a "perfect" power cord.

Anyway, my main point about the power cord being out of the circuit the vast majority of the time IN THE CONTEXT OF IT SERVING ITS PRIMARY FUNCTION was that I find it so very curious that people describe the effects of power cords in the exact same terms that they do with interconnects and speaker cables.

se
post #35 of 56
Quote:
Originally Posted by Chris J View Post

Power ground may be isolated from signal ground or common by diodes or resistors or capacitors.

Those techniques are used to isolate signal ground from the chassis, which in Class I chassis is tied to the mains safety ground. Not to isolate signal ground from the power supply ground.

se
post #36 of 56
Quote:
Originally Posted by elmoe View Post

Expectation bias. Do some kind of test and find out the horrible, horrible truth.

My wife and I were just comparing two power cords on the preamp. Had no expectations about how they would differ actually. We both heard the same differences at the same places, which are not that subtle. Not clear which is better, as there are things to like about both
post #37 of 56
Thread Starter 
Quote:
Originally Posted by elmoe View Post
 

 

Expectation bias. Do some kind of test and find out the horrible, horrible truth.

Apparently you didn't notice the rule that you are not allowed to mention DBT on this forum, to avoid starting arguments over the merits of DBT. I could go on at length about the problems of DBT but I won't. This forum is for people who take the effects of cables seriously and are interested in investigating the mechanisms. Your comment is more appropriate in Sound Science.

 

Mark

post #38 of 56
There must be a lot of *terribly* designed pieces of audio equipment out there if swapping appropriately rated power chords alters sound in any way.

I bet there are a lot of butthurt EE's out there when they hear that their circuit designs fail to perform under their target design conditions.

If MHz noise is leaking through the power supply and causing audible degradation, then you've got yourself a poorly designed piece of equipment, regardless of its retail price. If the power supply filter capacitance is too low to power through the low frequency signals, again, junk design.

Cheers
Edited by ab initio - 4/26/14 at 10:57am
post #39 of 56
Thread Starter 
Quote:
Originally Posted by gjc11028 View Post


My wife and I were just comparing two power cords on the preamp. Had no expectations about how they would differ actually. We both heard the same differences at the same places, which are not that subtle. Not clear which is better, as there are things to like about both

Yes, I've had plenty of listening sessions go against my expectations. Also had lots of independent confirmation by other's opinions when we deliberately didn't tell each other what we thought until after the test.

 

Mark

post #40 of 56
Quote:
Originally Posted by markheadphonium View Post
 

Yes, I've had plenty of listening sessions go against my expectations. Also had lots of independent confirmation by other's opinions when we deliberately didn't tell each other what we thought until after the test.

 

Mark

 

Yes I bet everybody who likes silver cables thinks they're "fast" and copper cables "smooth" without the need to tell each other beforehand. Let me guess: hi-end power cords sound "clean" and "electric". :D

Quote:
Originally Posted by ab initio View Post

There must be a lot of *terribly* designed pieces of audio equipment out there if swapping appropriately rated power chords alters sound in any way.

I bet there are a lot of butthurt EE's out there when they hear that their circuit designs fail to perform under their target design conditions.

If MHz noise is leaking through the power supply and causing audible degradation, then you've got yourself a poorly designed piece of equipment, regardless of its retail price. If the power supply filter capacitance is too low to power through the low frequency signals, again, junk design.

Cheers

 

Yes, it's pretty much as simple as that.

 

As for DBTs I am skeptical about the validity of such tests to begin with, so it wasn't necessarily what I meant. However when I hear things like "there are things to like about both power cords", my skepticism goes on a whole other level.


Edited by elmoe - 4/26/14 at 11:36am
post #41 of 56
Quote:
Originally Posted by ab initio View Post

There must be a lot of *terribly* designed pieces of audio equipment out there if swapping appropriately rated power chords alters sound in any way.

I bet there are a lot of butthurt EE's out there when they hear that their circuit designs fail to perform under their target design conditions.

If MHz noise is leaking through the power supply and causing audible degradation, then you've got yourself a poorly designed piece of equipment, regardless of its retail price. If the power supply filter capacitance is too low to power through the low frequency signals, again, junk design.

Cheers

 

A basic, textbook, simple linear power supply is not designed to block 1 MHz, it is only designed to filter noise below approx. 10-40 kHz, bandwidth really depends on the power supply caps.

 

I'll agree with you, that would be a poorly designed piece of equipment.Not too sure about the butthurt part, though! :D

post #42 of 56
Thread Starter 
Quote:
Originally Posted by elmoe View Post
 

 

Yes I bet everybody who likes silver cables thinks they're "fast" and copper cables "smooth" without the need to tell each other beforehand. Let me guess: hi-end power cords sound "clean" and "electric". :D

 

Yes, it's pretty much as simple as that.

 

As for DBTs I am skeptical about the validity of such tests to begin with, so it wasn't necessarily what I meant. However when I hear things like "there are things to like about both power cords", my skepticism goes on a whole other level.

Your comments are off-topic for the this thread. Have some respect for the what the OP (me) was asking, and if you aren't going to contribute, then take it to Sound Science. Thank you.

Regards,

Mark

post #43 of 56
Quote:
Originally Posted by markheadphonium View Post
 

Your comments are off-topic for the this thread. Have some respect for the what the OP (me) was asking, and if you aren't going to contribute, then take it to Sound Science. Thank you.

Regards,

Mark

 

My posts are on topic: "Effects of power cords" in which you state that you're "shocked" by the effect and ask why there is such a difference. My answer was that expectation bias was the reason for this, much like "silver" cables are expected to be "fast" and copper "smooth", power cords are "shocking". :D

 

If you're going to get defensive and have your feelings be hurt, you shouldn't ask... 

post #44 of 56
Quote:
Originally Posted by Chris J View Post
 

 

A basic, textbook, simple linear power supply is not designed to block 1 MHz, it is only designed to filter noise below approx. 10-40 kHz, bandwidth really depends on the power supply caps.


Certainly. The typical approach in circuit design is to place much smaller decoupling caps that do block the high frequencies at the supply terminals of any active parts susceptible to high frequency noise on the power lines. While they might not sit in the group of components on the circuit board that you'd draw a circle around and label "power supply circuit," they are still certainly an important part to proper power conditioning in the circuit design.

 

 

 

Cheers

Quote:
Originally Posted by Chris J View Post
 

I'll agree with you, that would be a poorly designed piece of equipment.Not too sure about the butthurt part, though! :D

 

I was thinking of this quote when I wrote about EE's getting butthurt when it is implied that their product is poorly designed: 

Quote:

From "Schitt Happenend," Chapter 12:

 Mike Moffat even posted (as baldr) an emotional tract, calling out NwAvGuy as a coward and a bully, hiding behind anonymity with unknown agendas. Perhaps a bit over-the-top, but I think it’s important to say that engineers are no less passionate about their products than an artist or performer. Attack the product, attack the person.

 

Cheers

post #45 of 56
I also am a true believer in the importance of the cord from wall socket to amp. I don't know why it seems to change the sound but it does. I was a sceptic until I tried different power cords. I do think different amps react different. Some amps maybe more power cord dependent.


The sensitivity of all the other equipment in the chain is also a factor in hearing power cord change outs. I still think it may be something difficult to measure and quantify though the statements in this thread are closer to what I feel is truth than what I have read here in years.

Cheers!
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