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Most obvious case of audio placebo ever.
extrabigmehdi
post Jun 7 2012, 03:16
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This is a bit old, but I thought this case of placebo is just mind blowing. I thought I would report it.

I've seen in a thread from head-fi some people complaining that the audio engine a2 speakers sounded muddy or things like that.

Then someone said:
QUOTE
By the design of the Audioengine's A/C Adapter, which is similiar to IEC's on various other electronic equipment (DVD players), the A2's short A/C cord can inserted one way or the other.
By finding the correct polarity this will improve the overall sound.


Then at least three person confirmed by inverting the power cord connection to a/c adapter it sounded so much better, and with all the audiophilia usual vocabulary.

Then I've objected :
QUOTE
This is dumb, there's no polarity with the alternating current, so putting the power cord in one way or the other is exactly the same. You are all victims of placebo.


And someone answered:
QUOTE
I do not claim I understand how it works and the scientific basis of it but I have tested it with my A2s, eg. the drums from my main reference (Jazz at the Pawnshop) particularly stood out as clearer, sharper, and more dynamic. It is so obvious that it cannot be placebo.


Well, it's just too obvious for me that's placebo, and three guy confirmed hearing an improvement.
Placebo is something strong.

The thread is not worth a reading, but here's the link anyway:
http://www.head-fi.org/t/503389/audioengine-a2-eq-settings
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A_Man_Eating_Duc...
post Jun 7 2012, 06:16
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Probably the only way they might listen to you is by emailing audioengine about it and post the reply.

OT: the person who posted the screenshot in that thread, wouldn't he\she be getting clipping for frequencies from 2k upwards?

This post has been edited by A_Man_Eating_Duck: Jun 7 2012, 06:28


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extrabigmehdi
post Jun 7 2012, 10:28
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QUOTE (A_Man_Eating_Duck @ Jun 7 2012, 05:16) *
Probably the only way they might listen to you is by emailing audioengine about it and post the reply.


The point is that myself don't have any doubt about the fact that it's placebo. A TV or anything doesn't work better , if you "invert" the power cord.
Despite that, you have some people defending that there's significant differences, and that "it can't be placebo".
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Willakan
post Jun 7 2012, 10:39
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"It's too obvious to be placebo": if I had a penny for every time somebody came out with that one...
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Kohlrabi
post Jun 7 2012, 11:21
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While I share your concerns about the claims by those people, I don't think we at HA should spend time dissecting all the bullshit which surfaces on Head-Fi, lest we spend all our waking time debunking the claims perpetuated there. It is well known that Head-Fi is not adhering to the same standards as HA. No one around here should have any doubt about the fact that the claim is completely bogus.

This post has been edited by Kohlrabi: Jun 7 2012, 11:22


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BrownRB
post Jun 7 2012, 13:15
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We Canadians can't try this as all of our power plugs are already polarized - one blade on the plug is larger than the other and can only be plugged in one way.

If polarity does not matter then why do we have polarized plugs? I'm guessing it is a safety issue?
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Arnold B. Kruege...
post Jun 7 2012, 13:38
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QUOTE (BrownRB @ Jun 7 2012, 08:15) *
We Canadians can't try this as all of our power plugs are already polarized - one blade on the plug is larger than the other and can only be plugged in one way.

If polarity does not matter then why do we have polarized plugs? I'm guessing it is a safety issue?


It *is* a safety issue.
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DonP
post Jun 7 2012, 13:45
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I've had gear where hum was affected by plug polarity. That's because one lead is hot and the other neutral.
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Willakan
post Jun 7 2012, 16:19
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On the subject of Head-Fi and plug polarity, it transpired that one of the most popular companies there (AudioGd) had been shipping all their equipment with power cords wired incorrectly (inverse polarity). There was a short thread, it got locked after a while and everybody forgot about it. Who cares about safety anyway?
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extrabigmehdi
post Jun 7 2012, 16:19
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Well , were I live , the connection to the power is symmetrical, I've never heard of polarized plugs, unless we are talking of a connection to earth, and then there's three plugs.
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bug80
post Jun 7 2012, 17:08
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QUOTE (DonP @ Jun 7 2012, 14:45) *
I've had gear where hum was affected by plug polarity. That's because one lead is hot and the other neutral.

Yep, I've had this happen also.
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Ouroboros
post Jun 7 2012, 17:47
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QUOTE (DonP @ Jun 7 2012, 13:45) *
I've had gear where hum was affected by plug polarity. That's because one lead is hot and the other neutral.
Being pedantic, it's because your earth is imperfect, and there is a potential difference between one or more of your equipment earth, your mains power supply earth and the grounding of your local neutral. One hot and one neutral doesn't implicitly generate any hum as a result of switching the poles, so long as your earthing is good.
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Ethan Winer
post Jun 7 2012, 18:22
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QUOTE (extrabigmehdi @ Jun 6 2012, 22:16) *
And someone answered:
... It is so obvious that it cannot be placebo.


They always say that, but they will never ever submit to a blind test. I went through this recently with a guy who should know better (pro recording engineer). He insisted the difference between two brands of external clocks was so obvious even a gerbil could tell. The guy lives close enough to me that I offered to visit him in person and let him tell me which clock was in use while I switched and he wasn't watching. He argued for weeks offering up every stoopid excuse, and in the end he called me a jerk and said that being associated with me will hurt his reputation. crying.gif

--Ethan


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mzil
post Jun 7 2012, 19:56
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QUOTE (DonP @ Jun 7 2012, 08:45) *
I've had gear where hum was affected by plug polarity. That's because one lead is hot and the other neutral.

I was going to say that too, but I had no evidence to back up my claim other than my recollection, so I didn't speak up.

Some gear in the 60's didn't have polarized plugs.

This post has been edited by mzil: Jun 7 2012, 20:14
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Carledwards
post Jun 7 2012, 20:19
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Complaining about placebo effect on head-fi is going after pretty low-hanging fruit, IMO. Awfully common over there.
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extrabigmehdi
post Jun 7 2012, 22:06
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Ok, here's a picture, so that it's more clear , look at the arrow:



Putting the power cord in one way or other in the ac adaptor should have no impact in sound quality.

But there's three guys in the thread that reacted strongly to the placebo. People are quite suggestible, when you think about it.
I know placebo is a quite common problem at hydrogenaudio, it's just surprising to see that placebo could be so efficient and so easy to induce.

This post has been edited by extrabigmehdi: Jun 7 2012, 22:07
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mzil
post Jun 7 2012, 23:06
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"AC Polarity Switch
One of the most effective methods for reducing hum is to reverse the polarity of the unitís AC connection.
However, AC plugs only fit into an outlet one way. The AC Polarity switch enables you to reverse the
AC polarity without moving the AC plug. The Normal position is usually correct, but if background hum
is audible you might eliminate it by moving the AC Polarity switch to Invert."

Parasound Phono Preamp Manual

Like many things, there's a grain of truth to some wacky claims. Hum level? Maybe. "Sound stage", etc?
I doubt it.

This post has been edited by mzil: Jun 7 2012, 23:32
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extrabigmehdi
post Jun 7 2012, 23:45
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QUOTE (mzil @ Jun 7 2012, 22:06) *
Like many things, there's a grain of truth to their wacky claim. Hum level? Maybe. "Sounstage", etc?
I doubt it.

Well at begin, there's an alternate current, without any polarity. The ac adaptor convert the alternate current, into continuous current, with a polarity.
If you switch position of power cord where the alternate current is coming from, i.e before being converted , it's exactly the same, unless I'm missing something.
Maybe after the continuous current is generated , we can change polarity of the generated continuous current , but the ac adaptor on audioengine a2 speaker doesn't allow this.
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BearcatSandor
post Jun 8 2012, 00:38
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QUOTE (Ouroboros @ Jun 7 2012, 10:47) *
QUOTE (DonP @ Jun 7 2012, 13:45) *
I've had gear where hum was affected by plug polarity. That's because one lead is hot and the other neutral.
Being pedantic, it's because your earth is imperfect,

Am i the only one who takes offense at that? What's wrong with my earth? What planet are YOU from, and just who do you think you are? Oh....right...you meant...right.

I do wonder how many horrible threads could be started by just making up the wackiest stuff we can think of. The other day, i was playing a CD by Breaking Benjamin. It was mastered WAY too loudly. However i have a fix for you all. If you take a special black marker and change the color of your positive speaker lead to black, it smooths out that distortion and it cools down the mastering. You know, it's no longer red so it's not so hot. Try it! it really works. I'll sell you the markers for $200.

This post has been edited by BearcatSandor: Jun 8 2012, 00:43


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Ouroboros
post Jun 8 2012, 00:41
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@mzil. Again, that's because of the various possible earth sources (equipment safety, local neutral, mains earth) being at different potentials, so you can get a small AC and/or DC current flowing around the imperfect (reactive and resistive) earth circuit. Swapping the live and neutral can reduce this, but it has nothing to do with one pole being "live" and one "neutral", it's because swapping them over can sometimes minimise the earth loop current flow, and hence the hum.
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Glenn Gundlach
post Jun 8 2012, 00:45
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In the OLDEN days it was common to have either a high value resistor or low value capacitor tying one side of the power line to the chassis. In that case reversing the power cord _can_ have an influence on hum levels. That SMPS brick does not any connection between the mains and output sides. Any changes are almost certainly imaginary but we do see and hear what we want/expect to see and hear.

G≤
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Ouroboros
post Jun 8 2012, 01:45
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Absolutely true on all counts. Trouble is, your neutral line is already tied to earth, either in your consumer unit, or at the last stage transformer - which I believe used to be on poles outside the property in North America (and in the movies they still are because they explode regularly during gunfights smile.gif), while in the UK I believe it happens back at the sub-station. Either way, these two earths (via the cap or resistor in the equipment PSU, and in the mains supply) will be at different potentials, so you get current flow, and that DC (or AC) current flow biases the transformer in the PSU and changes its performance, so you get hum.

In the olden days I spent many a happy hour pouring electrolytes (cold tea, sea water, urine, etc.) around ground spikes at telecoms installations to try to reduce the resistance/reactance and get the local earth potential to be closer to the mains supply earth to reduce hum, because that was far easier than digging out the earth spike and starting again, and far cheaper than installing an isolating transformer........ wink.gif. It was one of the first things the old installers taught me as a fresh-faced graduate - while I was busily trying to do the maths to work out how to fix the problem, they were "watering" the ground spike then going down the pub for a refill.......

This post has been edited by Ouroboros: Jun 8 2012, 01:48
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mzil
post Jun 8 2012, 02:38
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QUOTE (Ouroboros @ Jun 7 2012, 19:41) *
@mzil. Again, that's because of the various possible earth sources (equipment safety, local neutral, mains earth) being at different potentials, so you can get a small AC and/or DC current flowing around the imperfect (reactive and resistive) earth circuit. Swapping the live and neutral can reduce this, but it has nothing to do with one pole being "live" and one "neutral",

Oh, OK then, I'll fix my post where I said otherwise, right away. Oh, wait a minute, that's right. I NEVER MADE ONE.
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sld
post Jun 8 2012, 08:38
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QUOTE (Ethan Winer @ Jun 8 2012, 01:22) *
He argued for weeks offering up every stoopid excuse, and in the end he called me a jerk and said that being associated with me will hurt his reputation. crying.gif

--Ethan

When we dig up such cases, this is why. Such things hobble the progress of science. Such things also hobble the rational discussion of the relevance of the Bible in scientific matters, because it hurts reputation to be perceived as an "irrational-whatever", not knowing that the act of automatic exclusion is itself irrational.
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2Bdecided
post Jun 8 2012, 10:13
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QUOTE (extrabigmehdi @ Jun 7 2012, 23:45) *
Well at begin, there's an alternate current, without any polarity. The ac adaptor convert the alternate current, into continuous current, with a polarity.
The neutral sits at zero volts relative to earth, and the live cycles between +325V and -325V 50 times a second (Europe), or +156V and -156V 60 times a second (USA).

If you think there's no difference between zero volts and 325 volts then I have some career advice for you: don't become an electrician! wink.gif


Most modern appliances are double insulated. Their chasis and electronics nominally "float" relative to earth, and can easily be dragged down to (or up to) any other voltage they come into contact with. As others have described, there are practical limits to this, which means the polarity can make an easily audible (and sometimes, easily felt = tingle in fingers when equipment is touched!) difference.

It's kind of obvious to connect up equipment that can't be reversed first, and then connect up the other equipment using whichever polarity minimises the earth current (if present) along the signal interconnects. Even if they know about it, most people would only bother to do this if there was some audible or tangible problem.

As for sound stage improvement etc - no, I'm sceptical too. You can either go evangelise ABX testing to the world, or stay at HA. I know which is less frustrating. smile.gif

Cheers,
David.
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