130 replies to this topic

[MLXXX]

Recently we've had two monster sized threads on DTV Forum about the benefits of specialised power cords:

Multi-Channel Audio Systems / Advice On Power Cords
2-Channel Audio Systems / Bt At Kajak

The first thread was theoretical, and included requests for blind test evidence.

The second began with a report of an informal 4 or 5 trial blind test, which was not taken beyond the 4 or 5 trials because participants considered the differences made by the change in power cord were too obvious. (The device that had its power cord changed during the trials was a custom built DAC.)

In this third thread on power cords, I invite uploads of recordings of the output of power amplifiers or other audiophile devices playing the  same excerpt of music, where the only difference in playback conditions is a change in the power cord of an audiophile device.  This should allow all interested forum members to conduct their own private double blind ABX test using an ABX player such as foobar 2000. [Note, the ABX functionality for foobar 2000 may need to be added after installing the basic player.]

I am assuming that comparative sample recordings do not already exist on the web. Certainly I have noticed no sample recordings on websites of manufacturers of specialist power cords. If they already exist, they could shed light.

I suggest recordings be made at a sample rate of 48KHz to keep file sizes manageable. Recordings at a bit depth of 16 would be ok, but some people may prefer to record at 24 bits (provided of course the stereo ADC allows it).

With each pair of recordings I would suggest that the musical content of the two files be time aligned to the nearest sample, and the aligned files trimmed to identical lengths.  (This can be done, for example, using the free software, Audacity.) Files should start with a short period of silence in order to facilitate later ABX comparisons. A fade in may be appropriate. The silence and any fade in should be identical for both files.

It is the practice on some forums to limit links to recordings of non public domain material to excerpts of no more than 30 seconds. I myself cannot provide any advice whatsoever about copyright and any other legal issues regarding uploads. Members should consider these matters.

I suggest that unless you can hear a difference when you play your recorded files back and switch between them (say by using the mute and solo functions in Audacity), it may be sufficient to report that outcome to the forum, rather than uploading files that sound the same.  On the other hand, if you find material differences when inspecting recorded waveforms, then despite the differences being inaudible, an upload could well be of interest.

If recording the stereo output of a power amplifier connected to speakers, an attenuator will probably be required, as line level inputs to ADCs usually cannot tolerate high signal levels. For example, an 8 ohm speaker when driven with a sine wave at 8 watts will have 8 volts RMS across it. A series resistor, in conjunction with a shunting resistor across the ADC input, may do the trick. This is entirely at the risk of forum members. Warning: Don't treat loudspeaker level voltages lightly. They can deliver an electric shock, and incorrect connections can damage an ADC, or the power amplifier itself.

As for myself, I have no power amplifier with removable power cords.  About the best I could offer to do would be to make a pair of recordings with the presence or absence of a lengthy extension cord in the mains supply to a power amplifier, as the only variable.


Cheers,
MLXXX

P.S. There's a lot of scepticism regarding alleged improvements by special power cords.  Below is an example of that from an April 2010 thread on AVS Forum titled: Will a new power cord actually improve performance?

The OP asks:

Quote

So I'm listening to a local radio show today that discusses home theater, audio, video, etc. At one point they mention that replacing the factory power cord with an $80+ alternate power cord will improve performance and improve video quality. I think they mentioned the replacement cords should be solid core.

I've never heard of this before. True?

(note they also stated it would impove the quality of audio equipment too)

At post #15 of the AVS thread, a person claiming 34 years in the Electrical Contractor industry states this:

It's a scam, and people who should know better still fall for the marketing double-talk and parrot the information as if it's true.

Think about it, even with a $500 micro-strand 24K gold-conductor diamond-encrusted power cord, you're still plugging it into a residential builder's grade wall receptacle with tiny contacts in a house that has old Romex or knob-and-tube wiring, getting power from a cheap $5 circuit breaker in a panel that's getting unclean power from a transformer somewhere in your neighborhood that's getting it's power through a regulator in your utility company's local substation which gets it's power from a power plant that's possibly hundreds of miles away from your house.

Do you honestly believe that simply changing the last few feet of cable between your wall receptacle and your TV or Audio system will suddenly make your equipment look and sound better? The answer is NO.

It is only with hard evidence that this type of scepticism can be overcome, if indeed hard evidence can be found! If and when it is found, we may wish to explore what caused the audiophile equipment to perform differently.

Edited by MLXXX, 20 February 2011 - 02:21 PM.

[DrP]

All aside, these power cord threads (along with all other ludicrous products that claim simply unsupportable improvements in one thing or another) should cease.  There is nothing to be gained from them.  Those that believe the products work will not hear anything but praise for the products, no matter how loudly information to the contrary is shouted at them.

[rosewick]

DrP, on Feb 20 2011, 08:47 AM, said:

All aside, these power cord threads (along with all other ludicrous products that claim simply unsupportable improvements in one thing or another) should cease.  There is nothing to be gained from them.  Those that believe the products work will not hear anything but praise for the products, no matter how loudly information to the contrary is shouted at them.

Well written.

Eventually someone on this site writing the truth.

Beware of the wank factor.  

[MLXXX]

DrP, on Feb 20 2011, 07:47 AM, said:

All aside, these power cord threads (along with all other ludicrous products that claim simply unsupportable improvements in one thing or another) should cease.  There is nothing to be gained from them.  Those that believe the products work will not hear anything but praise for the products, no matter how loudly information to the contrary is shouted at them.

I personally find the first two threads to have a very low signal to noise ratio. (I found there were some scattered gems of posts, if a reader had hours to spare fossicking for them.)

With this new thread, there's an explicit invitation for those who insist there are clearly audible differences, to make recordings that other forum members can listen to. Well, excerpts.  Actions, not words.

I am not suggesting uploads be provided illustrating no difference. That would be child's play, and I agree it would do nothing to change the minds of the true believers.

I am suggesting that uploads be provided of audible differences* (if any audible differences exist). That would be quite something. And the next logical question would be: "why?".  Why is it that the particular audiophile device cannot perform the same with the power cord that the manufacturer of the device provided?

______________________

* What would be relevant would be audible differences under normal listening conditions, not artificial conditions such as steady test tones that are driving all of the channels in a multichannel amplifier to the point of clipping.

Edited by MLXXX, 20 February 2011 - 10:22 AM.

[:)]

oh here we go. our friends with the come leave us a "dump" mentality so we can examine the specimen by playing it back on our ghetto blaster clock radio.

what do we need this stupid thread for  

introduce more variables in the chain. oh they dont matter  

yeah do an upload download. so the armchair know it alls, who still cant be @rsed to get off their fat arses can pass their almighty judgement  

get out and experience for your self for flippin sake. is it so bloody hard if you are actually interested in it and its something you want to explore ?

people have offered to invite you into their home for a listen. people have been willing to lend you cables to try out for yoruself. people have shown its pretty easy to borrow a cable from a retailer if so inclined.

yeah I'll upload a dump alright  

and now the main reason for my posting !

  bloody hell how can someone in the right mind even suggest people hook up high level speaker level output to a recording device   are people lunatics here    

[myrantz]

:), on Feb 20 2011, 09:01 AM, said:

get out and experience for your self for flippin sake. is it so bloody hard if you are actually interested in it and its something you want to explore ?

Or, enjoy their very own MBL system at the very comfort of their own home..  

The Big Bang Theory said a quote I like lot though (when Sheldon was playing text based game) - the fastest graphics accelerator is the imagination, and by extension the most powerful general processor is the brain... Both a blessing and a curse, and he delivered that scene quite well...

And some journo think this show isn't funny...    It is funny right? I got a good laugh out of it...

[MLXXX]

:), on Feb 20 2011, 11:01 AM, said:

BLAH BLAH typical bluster and criticism BLAH BLAH

Al, there's nothing you've typed there that is worthy of a response, IMHO.

That was another of your non-constructive posts that we see every so often.  We'll very possibly get a similar post from bassett, if he's around.

I am seeking uploads illustrating the differences in sound power cords can (apparently) make, not invective.

Edited by MLXXX, 20 February 2011 - 11:25 AM.

[:)]

treblid, on Feb 20 2011, 12:13 PM, said:

Or, enjoy their very own MBL system at the very comfort of their own home..  

~

thats right treb, why do we ever need to get out and try experience the wonder, beauty and sonic splendour of systems like that  

yes why when can just watch it on youtube instead  

should please the armchair know it alls a treat no doubt. the best systems in the world all at the finger tips to enjoy via youtube, dont even need to get out from behind the computer screen and keyboard  

[myrantz]

:), on Feb 20 2011, 09:30 AM, said:

thats right treb, why do we ever need to get out and try experience the wonder, beauty and sonic splendour of systems like that  

yes why when can just watch it on youtube instead  

Agreed.

Look MLXXX I don't mind what you're saying, and I thought it is a good idea when I read sample recordings. I thought you are using your digitising know how ot create sample recordings for people to playback on their system...

Turns out you're just standing on a soapbox.. Good luck finding one or many, and as mentioned in the other thread, it will still not end the debate because people will argue about their gear again..

[MLXXX]

treblid, on Feb 20 2011, 11:46 AM, said:

Look MLXXX I don't mind what you're saying, and I thought it is a good idea when I read sample recordings. I thought you are using your digitising know how ot create sample recordings for people to playback on their system...

Turns out you're just standing on a soapbox.. Good luck finding one or many, and as mentioned in the other thread, it will still not end the debate because people will argue about their gear again..

I remind you: all my power amps have non-removable power cords.

As for other devices: my blu-ray player has a removable power cord but there is no earth; my HTPC has a three pin removable power cord; my various CD players have built in cords; an old DVD player has a removable plug with no earth.

I have no "special" power cord.

I guess I could borrow a "special" power cord, or assemble one myself.

I could then make a pair of recordings [of the output of my Blu-ray player or my HTPC or my old DVD player] and then listen intently for differences (e.g. with my Asus Xonar Headphones Sound Card and Sennheiser HD800 phones). And if I heard differences, upload the files.

Trouble is, it's unlikely I would hear a difference with a special power cord. The Blu-ray player is just standard equipment, as is the motherboard of the HTPC and the Power Supply Unit that powers the motherboard; and the old Pioneer DVD player is standard equipment.

It seems to me more logical and efficient that those people who have already heard a difference, make a recording, especially if the difference is "night and day".

As I've mentioned in this thread and another thread, recording the output of a power amp can be tricky if connecting direct to the speaker outputs. However  some amps run the headphone socket from the speaker output of the power amp (using a handful of resistors).  If you hear a difference at the headphone socket then you may be able to take the audio from there.

Note: I really don't want this thread to degenerate into an unfocused talkfest. If someone can upload some files for members to listen to, illustrating what difference a change in power cord can make, I'd be much obliged.

Edited by MLXXX, 20 February 2011 - 01:55 PM.

[gone_bush]

:), on Feb 20 2011, 12:01 PM, said:

are people lunatics here

Al, you should know better than to ask leading questions in a thread talking about cables. Shame on you!!!

[:)]

gone_bush, on Feb 20 2011, 02:47 PM, said:

Al, you should know better than to ask leading questions in a thread talking about cables. Shame on you!!!

sorry GB

just trying my best to save someone blowing up their equipment in the process or even worse themselves with what some numbskulls suggest  

[MLXXX]

:), on Feb 20 2011, 01:56 PM, said:

sorry GB

just trying my best to save someone blowing up their equipment in the process or even worse themselves with what some numbskulls suggest  

Said "numbskull" provided a warning in red.

[bassett]

MLXXX, on Feb 20 2011, 12:25 PM, said:

That was another of your non-constructive posts that we see every so often.  We'll very possibly get a similar post from bassett, if he's around.

Well that's just typical, When all else fails kick the Dog, and you just might get a reaction.  Unfortunately like all your other attempts
at enlightenment, it lacks an substance.
You bang the drum, a bit like a parasite at a revival meeting, marching up and down, and yelling out "Hallelujah" But  then offer no
examples of what you want other people to supply, Why isn't anyone surprised at  your complete lack of substance in supplying an
audio sample, yourself.
No doubt this thread will rattle on like the other two threads and go precisely no where, as the other two threads did.

I dare to ask you the following question,  Is it possible to load an audio file on his forum,  And if indeed it is possible, why
haven't you  loaded one.

[MLXXX]

bassett, on Feb 22 2011, 08:39 AM, said:

I dare to ask you the following question,  Is it possible to load an audio file on his forum,  And if indeed it is possible, why
haven't you  loaded one.

It's possible to upload a WAV file in the attachments part of the forum, but not the lossless compressed FLAC format. An external site would offer better scope for longer samples.

I haven't uploaded any myself because I haven't heard the effect. My AVRs have fixed power cords.

[jsmith]

MLXXX, on Feb 20 2011, 02:36 PM, said:

...especially if the difference is "night and day".

If the difference is "night and day" as some have described their experience with power cords, then this should be evident as you say, even in a captured FLAC file.  I do agree though with some points made in this thread that a PC soundcard etc., can't capture the subtle nuances of people systems, which is very true, but surely not required when there is such a marked difference as described in the kettle cord thread.

JSmith  

[myrantz]

jsmith, on Feb 22 2011, 09:59 AM, said:

If the difference is "night and day" as some have described their experience with power cords, then this should be evident as you say, even in a captured FLAC file.  

I do agree though with some points made in this thread that a PC soundcard etc., can't capture the subtle nuances of people systems, which is very true, but surely not required when there is such a marked difference as described in the kettle cord thread.

linky.. hee hee...

FLAC is a loseless compression algorithm, but ADC is a lossy operation. And attenuating output from power amplifier to line level again is not a linear operation in general.

But admittedly this is all theory so I'm hoping somebody will try it and prove me wrong... Probably MLXXX as he seems to know how to do it..

People with a home studio setup can probably do this I guess. But then we'd be back to playback variations. For all I know you probably need a "special" cable to hear the difference with these recordings..

Edit: Another video from HongKong probably. Listen to how a TT sounds with special power cables...    Unfortunately he don't have a video using normal cables so we can't make a comparison.

Edited by treblid, 22 February 2011 - 01:43 PM.

[Drizt]

MLXXX,

I know you can't compare power cords (due to your devices having fixed cables) but perhaps it would help to get the ball rolling if you can do the proposed comparisons on something else.  E.G. compare the outputs when using two different CDP's (level matched as best as possible).

[MLXXX]

Drizt, on Feb 22 2011, 02:13 PM, said:

MLXXX,

I know you can't compare power cords (due to your devices having fixed cables) but perhaps it would help to get the ball rolling if you can do the proposed comparisons on something else.  E.G. compare the outputs when using two different CDP's (level matched as best as possible).

Hi Drizt, I'm normally in agreement with your viewpoints but I'm a little stuck with understanding why you think it would be helpful for me to capture the analogue output of two CD players (if that is what CDP stands for). As you say there would be a level matching issue.  Can you please explain why you feel such an exercise would help?


I've been thinking more about "controls" for power cord recordings, I think something along these lines would be useful:

1. Find a passage of audio that sounds different when played with different power cords to the power amplifier.
2. Have a pc play that passage in an endless repeating loop (say 5 to 15 seconds worth).
3. Make 4 recordings in quick succession of the passage A1, B1, A2, B2, where A is with one power cord and B with the other.  Upload all 4 recordings (after they are time aligned and trimmed).

This will give an indication of the very minor variances (at the level perhaps of noise below perhaps the 16th most significant bit) between A1 and A2, and between B1 and B2. But a much greater (and audible) difference will be present between A1 or A2 on the one hand and B1 or B2 on the other hand.

Alternatively I guess you could just upload A1 and B1 and comment that your controls A2 and B2 were so close to A1 and B2 respectively as not to be worth uploading.

[gone_bush]

Now let me see if I've got this correct. We are going to compare A1, B1, A2 and B2? *

As we all know, B1 & B2 are the names of characters on an ABC kids show. Since they are bananas, I can only assume that A1 & A2 are apples from some rival show.

So how are we supposed to compare apples and bananas?

* Yep, I'm taking the p1ss as all I can see happening is that this thread becomes another behemoth of irrelevant crap.

[:)]

gone_bush, on Feb 22 2011, 07:44 PM, said:

~ I can see happening is that this thread becomes another behemoth of irrelevant crap.[/size]

What do mean becomes ?.  

..isnt it there already  

[MLXXX]

treblid, on Feb 22 2011, 01:34 PM, said:

FLAC is a loseless compression algorithm, but ADC is a lossy operation.

I believe a lot of multichannel power amps these days accept analogue input, use an ADC, do their digital processing, then convert back to analogue with a DAC before the power amplification. Purists prefer to bypass this.  We have to remember that the microphones capturing a performance need an ADC, or at least the analogue mixer does.  ADCs are everywhere!

I have read of experiments of a switch that enabled listeners to hear an analogue source direct, or via an ADC to DAC signal path, and the listeners couldn't tell the difference.  The loss/distortion of a modern ADC is very very small for the human ear.

Quote

And attenuating output from power amplifier to line level again is not a linear operation in general.

On the contrary, it is for practical purposes linear.  It will be closer to linear than a typical DAC.

____________

The circuit required is extremely straightforward.  Assume the power amp channel can supply 80V RMS to an 8 ohm load. That corresponds to a power of 80 x 80 / 8 = 800W (yes a very powerful amplifier, rather more power than likely to be used domestically!).

Assume the line input of the ADC can handle up to 800mV RMS comfortably and has an input impedance of 50KΩ. We need a reduction in voltage to 1/100th: from 80V RMS to 800mV RMS. Choose a shunt resistor of 2.2K (across the input to the ADC) and a series resistor (to the power amp output) of 220K, as a close approximation.  The power dissipation capability required for the 220K will be given by 80 x 80 / 220,000 = 0.029W. An eighth watt resistor would do; a quarter watt resistor for good measure.
Caution: do not treat power amplifier speaker output voltages lightly.  Make a mistake and the consequences could be life threatening, and expensive.

Edited by MLXXX, 22 February 2011 - 08:08 PM.

[Drizt]

MLXXX, on Feb 22 2011, 07:35 PM, said:

Hi Drizt, I'm normally in agreement with your viewpoints but I'm a little stuck with understanding why you think it would be helpful for me to capture the analogue output of two CD players (if that is what CDP stands for). As you say there would be a level matching issue.  Can you please explain why you feel such an exercise would help?

I was just thinking that people seem reluctant to contribute if the OP hasn't done it himself (added measurements/files to this thread).  It doesn't really matter what you compare as long as you can give an example of what you are asking for.  That is all I was trying to get at.  Sorry if it wasn't clear.

[gone_bush]

:), on Feb 22 2011, 07:56 PM, said:

What do mean becomes ?.  

..isnt it there already  

I hate it when you're right!  

[ajm]

:), on Feb 22 2011, 07:56 PM, said:

What do mean becomes ?.  

..isnt it there already  

What do you want Al?  You bitch and moan saying no one will do anything then bitch and moan when someone tries something.

Really not enjoying seeing you get like this.