[Niteshade]

I have logged hundreds of hours in various labs. My entire CoOp was done in a lab. Experiments have to be reproducible to hold value. The test fixture in Browntrout's example can be easily reproduced and will yield similar, if not exact results to whomever wants to try it. This is most likely why the tests were acceptable.  (Sounds like I'm playing Devil's advocate!  )

Not really....

How equipment works in real life is often very different from the way it works in the lab. The kinds of noise we have on our lines is going to be different, the voltage and current issues will be different as well. The loads will be different and certainly not non-inductive 50 ohm precision resistors.

Testing power altering equipment on audio equipment should be done with real-life scenarios, after the lab tests. A/B testing should be done at the speaker outputs, preamp outputs...whatever. Using a signal generator to inject noise before the filtering/conditioning, etc..device in question isn't such a bad idea either. Maybe just plugging something known to be nasty in the line before the conditioner/cord/filter would work even better. (Fence charger, microwave oven, neon sign, etc...). 

Real-life testing with various conditions would appease many people. Stopping at the lab leaves too  many unknowns.

[turkey]

I just read the full white paper.

It contained much more detail, but didn't really answer any more questions than did the short "abstract."

I also wonder who Ben Duncan Research are, and how they are related to Russ Andrews and the sale of these AC cords.

[*Scotty*]

I would like to see X millivolts or microvolts of noise injected before the power-cord or line conditioner and then an after measurement at the input of the power transformer. This would directly tell you how much RF was removed. What this doesn't reveal is the DUTs impact on the dynamic impedance that the load looks at. If this is increased you will hear a loss of dynamic life and a rolling off of the HF. One of the best ways to demonstrate the impact of filter element saturation is to put a 1 amp rated Corcom filter in line with your power amp. If the same filter poles are implemented with 15 or 20 amp rated inductors the problem will be mostly eliminated,you can still have a problem if the filter poles are too close to the audio band but this is a separate issue. BEGINNING OF RANT[ Every time I see a power conditioning product claiming to reduce RFI with absolutely no accompanying proof of performance except marketing claims , user testimony or internet "BUZZ" I amazed by peoples willingness to purchase them. One of the most outrageous claims to date is that a filter placed on power line takes days to"settle in" thus neatly avoiding an AB test of effectiveness in realtime. END OF RANT] Once again the easiest Qualitative test I can think of is to look at the powerline waveform on an oscilloscope making note of how much fuzz is riding on the 60Hz sinewave and then looking at it after the filter is in place at the point of entry to your gear. If it takes away some of the fuzz, you have accomplished a level of RFI reduction. 
Scotty

[turkey]

One of the most outrageous claims to date is that a filter placed on power line takes days to"settle in" thus neatly avoiding an AB test of effectiveness in realtime.

This is a favorite trick of many vendors, not just filter vendors.

In essence, it's also the whole justification for saying that AB tests are flawed.

[NewBuyer]

This thread struck a nerve for me because it is the "marketing masquerading as science syndrome".   It just leads the consumer to think that engineering and science are pretty much useless tools in developing good sound.   That is unhealthy for the industry.  It leads to bad products at very high prices.   It pretty much insures that high-end audio will forever be a small inconsequential industry.

Agreed on all counts.

This thread reminds me of another in a different forum a few months ago. As I recall it ended up being locked.

Anyway, in that thread someone offered what he claimed was proof that an expensive power conditioner was effective and thus a useful purchase. The "proof" was examining the AC power to an amplifier with and without the filter device connected. With the filter in place there was a miniscule reduction in high frequency grunge on the AC line. So I pointed out that the proper place to look for an improvement is at the amplifier's speaker output terminals. Man was he PO'd at me!

I too am reminded of another forum where the user was testing the products of a well-known company that makes power conditioners and a premier power regenerator.  Turns out that the harder those products needed to work to 'clean' the AC, the more junk those products also pumped directly back into the AC line, thus making the AC line problems actually much worse for all other equipment not directly connected to their products.  Then somebody mentioned looking for improvements at the amp's speaker terminals - and while apparently there was less HF/RF going into the power inlet, there was no significant difference before/after at the amp speaker terminals.  The bigger surprise was when he then measured the before/after at the terminal end of the speaker wire at the speakers themselves - and found that it was measurably worse there, when using the products.  It appeared that the junk the products were putting back into the AC line, was heavily radiating from all attached power cords and the in-wall AC line - then being picked up by the speaker wire, and consequently presenting itself to the speakers along with the amplified signal.  Audible degradation was claimed.

I have since wondered that if the back-flow junk radiating from the power cables and in-wall AC line when using those products was heavy enough to get picked up and propogated by speaker wire, it must likely cause even more audible damage in any unbalanced signal cables and interfaces...

[*Scotty*]

My own opinion is that while powercords and conditioning are worth while adjuncts to achieving a high quality of music reproduction there is ample potential in the  marketing and the subsequent purchase of these products to loose sight of an essential fact. Power conditioners and powercords will not turn a BOSE WAVE RADIO into a High Fidelty device. Like wise, it won't transform a mediocre preamp or any other mediocre piece of gear into world beater. As a matter of logical prioritization you should first purchase the best designed and sounding circuits that you can.  With better design comes superior PSRR , which reduces their susceptibility to noise from the power supply, hopefully reducing the need for radical/expensive power conditioning solutions. You can also chose a circuit which, if RFI is present with the signal does not amplify it. As an example the circuit in my preamp is a buffer with around a 10 mHz bandwidth and it will pass the RF through without interacting with it. There are no downward intermodulation products from RFI present in audio band.
Scotty

[*Scotty*]

If the speaker cable picks it up it will only be a problem if it can find its way back into the amplifiers feedback loop. Most amplifiers have a Zobel network or filter network which bandwidth limits what can come back into the amp from the speaker cables. I would not have looked for RF at the amplifiers terminals it should not be present unless the amp operates at radio frequencies or it is oscillating.
What might have been measurable is increased intermodulation distortion at the output of the amp, a very small increase in IM distortion is very audible and very objectionable. 
Scotty

[Ethan Winer]

the easiest Qualitative test I can think of is to look at the powerline waveform on an oscilloscope making note of how much fuzz is riding on the 60Hz sinewave and then looking at it after the filter is in place at the point of entry to your gear. If it takes away some of the fuzz, you have accomplished a level of RFI reduction.

Again, all that matters is what happens at the audio output of your equipment. Most electronic gear is designed well enough to reject normal amounts of junk coming in on the power line. Such junk is a problem only if it ends up at the audio output.

--Ethan

[*Scotty*]

Ethan ,You have made a sweeping generalization with this statement,

Again, all that matters is what happens at the audio output of your equipment. Most electronic gear is designed well enough to reject normal amounts of junk coming in on the power line. Such junk is a problem only if it ends up at the audio output.--Ethan

.
While this assertion appears superficially true,upon further examination we find that it is unsubstantiatable, there is no quantifiable amount of "normal junk on the power line". This generalization is not a valid argument against some form of external power line filtering. As I said in a previous post the RFI that makes it into the component has the potential to increase intermodulation distortion and it doesn't take much additional IM to result in audible degradation.
Scotty

[Ethan Winer]

the RFI that makes it into the component has the potential to increase intermodulation distortion and it doesn't take much additional IM to result in audible degradation.

Okay, but if that's true it is still measurable at the amplifier's output terminals! So you measure IM distortion at the amplifier's output with and without the power line filter in place, and there's your answer.

--Ethan

[whubbard]

I've got to agree with Ethan...
If you can't see/find/measure anything on the amplifier output, who cares?

-West

[turkey]

I've got to agree with Ethan...
If you can't see/find/measure anything on the amplifier output, who cares?

-West

I think what Scotty was pointing out that there is no standard amount of RFI, so an amplifier (or for that matter an external filter) that works fine in one environment may not work well in another environment.

We should also note that an external filter may or may not help the situation, depending upon the environment.

This is actually one of the things I felt was wrong with the material presented by Browntrout. It assumed that all the RFI would be entering the AC mains before the power cord.

[kyrill]

Following this discussion what mostly is based on what do measurements show ( as if they are the objective truth) and what can be heared. ( which should be subjective)

What i miss are the underlying assumptions which control the discussion and NOT the topics in texts.
assumption one: Because people have the property to hear what you want to hear -A nice case is Kevins example of the random +/- lettering on the caps- almost by definition what people claim to hear cannot be trusted so only measurements can tell the real truth. This is a gross generalization and as a truth not a truth at all. I do know of many naked women who only want to have a shower. So may i take the stance naked women by definition are beyond man's desire?

The second assumption : only measurements tell the truth you can trust. This is only true for old knowledge.  As you can only measure for what you already know.
You cannot measure for a thing you dont (even) know that it exists. You may discover different or new patterns of known variables, but extremely hard to find a new source variable. For instance if you do not know that jitter exists, EE will not measure it to explain the harsh beginning of the CD era, EE even proofed at that time that digital sounded better!! Still most people could easily hear the rotten sound of digital and those massive amount of subjective data forced the industry to find eventually the jitter phenomena.

Measuring cables to explain hearable differences is on the same track. You cannot measure in the cable for that specific phenomena that explains why it sounds (so much) better if that phenomena is not discovered yet ( if it exists!) So measuring a (filtered) cable and finding minuscule reductions that not possibly can explain its better sounding is not a scientific proof but a belief. Very possible is the fact it does sound better but industry does not yet know what to measure for.

[Ethan Winer]

you can only measure for what you already know. You cannot measure for a thing you dont (even) know that it exists.

It is very easy to measure audio for parameters that are not yet known! Not that there are any. But it's not only possible, but easy. The method is called a null test, where the output of the Device Under Test (DUT) is subtracted from its input. Any artifacts or other differences - whether expected or not - are easily seen. And since the differences are isolated from the music, they can be easily analyzed. This technique has been known for many years, which is why I'm confident there are no new parameters.

if you do not know that jitter exists, EE will not measure it to explain the harsh beginning of the CD era, EE even proofed at that time that digital sounded better!! Still most people could easily hear the rotten sound of digital and those massive amount of subjective data forced the industry to find eventually the jitter phenomena.

This is not at all what happened with early digital. Jitter has never been an audible problem. My Artifact Audibility Report lets you assess for yourself the audibility of soft artifacts like jitter, and I urge you read it and listen to the examples. The crystal oscillator in even the cheapest motherboard sound card or Walkman CD player is literally 1,000 times more stable than any analog tape deck or LP turntable. Yet you never hear people complain about those analog technologies. Just yesterday I had occasion to analyze the stability of a very expensive turntable. Besides constant wow that was easily seen (if not heard) using digital audio software, the overall speed varied by 1/4 second from one play to another over only five minutes.

When CDs first came out, the vast majority of consumers - and audio professionals - accepted them as vastly superior to LPs and cassettes. But there are two reasons early digital sounded "harsh" to some people:

1) They weren't used to hearing a truly flat and extended high end response, so compared to cassettes and LPs the CDs sounded harsh.

2) Some early CDs were made from the same masters that were used for LP records. When mastering LPs, engineers add high-frequency limiting to avoid burning out the expensive cutter head. This limiting can also add a glassy sheen to the high end, which some people to this day mistake as LPs sounding "better" than CDs. LP masters also have high frequency boost to overcome the HF loss on the inner grooves. So when the processed tapes were transferred to CD, they were indeed harsher than the original masters. But engineers soon realized they didn't need to do that extra stuff for CDs, and this has never been an issue since.

Very possible is the fact it does sound better but industry does not yet know what to measure for.

Again this is highly unlikely. But you are not the first person to claim his hearing trumps known audio science.

If you can identify a new as-yet-unknown audio parameter, I promise a Nobel prize is in your future. But I'll extend that further, and offer you $1,000 out of my own pocket, with all of audio circle as a witness.

--Ethan

[bpape]

There is a big difference between jitter in a digital system and speed stability in an analog system.  In the analog world, it will change pitch slightly.  In digital, it can cause bits to be misread if the clock isn't synched to the data stream -  1's read for 0's, bits skipped causing errors in the word boundaries, etc.  If it's the LSB, then it likely isn't a big deal - but could be in the case of word boundary issues.  On the other hand, when you get into the more significant bits, it can drastically change the value of the data word.

When binary data is read, it's reading a voltage at a specific point in time.  There is a transition period between the 1 and 0 where voltage is in between the 2 values.  At that point when it's read, there is some error allowed where the firmware will simply round.  When you're in between though, it 'guesses'.  Yes.  It can be good at guessing but not perfect. 

This has nothing to do with the original topic but thought it needed to be addressed.

Bryan

[kyrill]

you can only measure for what you already know. You cannot measure for a thing you dont (even) know that it exists.

It is very easy to measure audio for parameters that are not yet known! Not that there are any. But it's not only possible, but easy. The method is called a null test, where the output of the Device Under Test (DUT) is subtracted from its input.
Your defence is (still) locked in the domain of previous thinking. The device that measures is NOT an intelligent all knowing observer. It is a "dumb" machine pre-programmed and pre instructed, in fact it is only designed to only measure  variables that the machine can handle. Anything that is beyond the existing knowledge of the engineer is not part of that machine.  It surprises me that you cannot let loose the idea that man cannot measure for what he does not know yet. Another example than the jitter example. Some years ago in Switzerland Bayer a pharmaceutical multinational spilled hectoliters of a purple liquid on the dockside  of the river during loading on ships . Tens of thousands of fish were killed and that river ends its journey through Germany into Holland to meet the sea in Rotterdam. Amsterdam purifies a part of that water of the river Rine for tap water. So an engineer wanted to know how many ppm of that chemical was in the water intake into their purifier systems. The rapport made by the local staff showed zero ppm of that compound: 0 ppm. Until a clever local engineer uttered, maybe the machine was never designed to find that chemical. They had to change the machine in order to measure for that chemical. It shows machines can only measure for what they are intended for. And your EE reasoning reaches all compassing knowledge in the sentence ( see red)
 Any artifacts or other differences - whether expected or not - are easily seen. And since the differences are isolated from the music, they can be easily analyzed. This technique has been known for many years, which is why I'm confident there are no new parameters. Of course BUT only within the limits of the existing machine -->knowledge

if you do not know that jitter exists, EE will not measure it to explain the harsh beginning of the CD era, EE even proofed at that time that digital sounded better!! Still most people could easily hear the rotten sound of digital and those massive amount of subjective data forced the industry to find eventually the jitter phenomena.

This is not at all what happened with early digital.

?? Are you sure this is wide based consensus?
Jitter has never been an audible problem. My Artifact Audibility Report lets you assess for yourself the audibility of soft artifacts like jitter, and I urge you read it and listen to the examples. The crystal oscillator in even the cheapest motherboard sound card or Walkman CD player is literally 1,000 times more stable than any analog tape deck or LP turntable. Yet you never hear people complain about those analog technologies. Just yesterday I had occasion to analyze the stability of a very expensive turntable. Besides constant wow that was easily seen (if not heard) using digital audio software, the overall speed varied by 1/4 second from one play to another over only five minutes. you compare apples with oranges. digital jitter in consumer machines is not heard as wow and flutter in the digital domain but as lack of depth, and musicality and added electronic harshness

When CDs first came out, the vast majority of consumers - and audio professionals ( that is a REAL pity and product of expensive marketing techniques) ) - accepted them as vastly superior to LPs and cassettes. But there are two reasons early digital sounded "harsh" to some (some??) people:

1) They weren't used to hearing a truly flat and extended high end response, so compared to cassettes and LPs the CDs sounded harsh.
This is a very arrogant and false statement for what they and I heard
Why?
Dear Ethan ALL PEOPLE listen  ALL DAY long to the the most extended and perfect HIGH END systems EVERY DAY of THEIR LIFE. It is such a PERFECT system that no manufacturer can even dream of even coming close: REAL LIFE SOUND. This is a reference build in us long before we are 5 years old. Just compare whatever system you listen to to what you normally hear. Some audio engineers are so theoretical that they live completely bypassing this reference. Others and me for instance Hary Pearson from the Absolute Sound, do not compare LP's to Cd's but each apart to real life performances. Until today it is still obvious the LP out performs any cd to that regard.

2) Some early CDs were made from the same masters that were used for LP records. When mastering LPs, engineers add high-frequency limiting to avoid burning out the expensive cutter head. This limiting can also add a glassy sheen to the high end, which some people to this day mistake as LPs sounding "better" than CDs. LP masters also have high frequency boost to overcome the HF loss on the inner grooves. So when the processed tapes were transferred to CD, they were indeed harsher than the original masters. But engineers soon realized they didn't need to do that extra stuff for CDs, and this has never been an issue since.
Well so much for your golden ears

[quote]Very possible is the fact it does sound better but industry does not yet know what to measure for.

Again this is highly unlikely. But you are not the first person to claim his hearing trumps known audio science.

If you can identify a new as-yet-unknown audio parameter, I promise a Nobel prize is in your future. But I'll extend that further, and offer you $1,000 out of my own pocket, with all of audio circle as a witness.
--Ethan[/size]
[/quote]

[*Scotty*]

 kyrill,The only way to win this battle is to not to fight it.
Scotty

[turkey]

kyrill,The only way to win this battle is to not to fight it.
Scotty

Yes, he was fighting a losing battle.

[kyrill]

Yes, he was fighting a losing battle.

Is that a fact? Audio Circle community is  about "ears are deaf and what you see ( measurements)  is what you hear?

By the way isn't it rather strange that  the "eye" has the arrogance that it knows what you should hear?

As if  visual information is the fundamental basis of what you hear?? Think about it and try to apply it to the other senses

measurements which produces in the end visual information about sound  produce a metaphor at its best and in many other cases irrelevant data in relation to hearing experiences. For instance it so easy to make visual,  harmonic distortion, so many EE designers went for 0.004% and lower distortion as if that should sound (much) better. In that case all tube lovers would be idiots

[Niteshade]

http://stereophile.com/thinkpieces/165/

Take a look at this. Fits in-really!