Cable burn-in: Is it real or imagined?
- Thread starter Johnny Vinyl
- Start date
So when you make changes in your system that require reconnection, and by default therefore bending or reshaping your cables as you put them to the side, is previous burn-in erased and one must start over?
John
IMO the answer to all things is to keep an open mind. However if we use this as a reason that people believe in burn in, this is thrown back as well usually with a smiley of some sort following that this was nonsense as well
For my ears there is a difference with cable burn in
This debate has gone on here since this forum was launched. It has the same proponents and the same opponents. I say let "your" ears be the judge
Frankly I get bored of hearing the verbage from the same people (both sides) on the same subject. I was the biggest cable skeptic and if you asked me this time last year if I was content with my system, the answer would have been a resounding yes. All of my cables were pushing 10 years old. I was in hog's heaven until I purchased some power cords last year and was startled that I could hear a difference after 2-3 days of burn in. This was not expectation bias as I had every opportunity to audition the cable and to return it if I wasn't pleased. I had nothing to prove to myself as I was quite content with my system
Of course the naysayers will say that I had expectation bias or that there were no measurements or no DBT was done -----yawn
Frantz, you have your opinion and I suppose we have ours.I respect yours. Whenever I see posts in a thread with such a topic, predictably the same people will post only to say the same thing----double yawn. It seems both sides are preaching to the choir
I respect other people's opinions and I'm impressed that this thread hasn't self destructed yet
IMO the answer to all things is to keep an open mind. However if we use this as a reason that people believe in burn in, this is thrown back as well usually with a smiley of some sort following that this was nonsense as well
For my ears there is a difference with cable burn in
This debate has gone on here since this forum was launched. It has the same proponents and the same opponents. I say let "your" ears be the judge
Frankly I get bored of hearing the verbage from the same people (both sides) on the same subject. I was the biggest cable skeptic and if you asked me this time last year if I was content with my system, the answer would have been a resounding yes. All of my cables were pushing 10 years old. I was in hog's heaven until I purchased some power cords last year and was startled that I could hear a difference after 2-3 days of burn in. This was not expectation bias as I had every opportunity to audition the cable and to return it if I wasn't pleased. I had nothing to prove to myself as I was quite content with my system
Of course the naysayers will say that I had expectation bias or that there were no measurements or no DBT was done -----yawn
Frantz, you have your opinion and I suppose we have ours.I respect yours. Whenever I see posts in a thread with such a topic, predictably the same people will post only to say the same thing----double yawn. It seems both sides are preaching to the choir
I respect other people's opinions and I'm impressed that this thread hasn't self destructed yet
Question: Microseconds seems like an unreasonably short period of time to measure current?
Answer: Since power supply rectifiers pull current in pulses and the pulse duration is typically less than 10% of the duty cycle, the conduction period is typically 200-800 microseconds. The time scale for the graphs is about 50 microseconds from beginning to end. Notice that the slope of the measured waveforms levels out and stabilizes within that 50 microsecond timeframe. Therefore, it is unnecessary to display information beyond the 50 microseconds. In other words, the measured differences would be the same even if we extended the time period beyond that shown.
The point is that there ARE measurable differences between power cords including different gauges of wire, connectors and different geometries of wire.
I don't want to hijack your thread and all the fun you are having but some of this might be helpful.
Some of you have basic misunderstandings about AC power delivery and power rectification specifically. Without some basic knowledge you will never understand the subject.
It is necessary to understand the manner in which power supplies in consumer electronics function. The integrated circuits in consumer electronics require several DC voltages to operate. It is the job of the power supply to convert alternating current (AC) from the wall outlet to direct current (DC) voltages that supply power to the component's electronic circuits.There are basically two types of power supplies: transformer and transformer-less (switched mode) power supplies. Both use rectifiers that are essentially electronic switches that alternately turn on and off in response to the input AC voltage. It is the rectifiers that convert the AC voltage to a pulsating DC voltage.. This voltage is stored and filtered by the power supply storage capacitors that provide the relatively stable DC voltages to the PCBs and integrated circuits.Unlike a light bulb, fan or simple motor, audio/video power supplies do not pull current in a constant or linear fashion. Rather, they pull current in instantaneous pulses as the rectifiers switch on to fill the storage capacitors. This is as true for low current devices such as CD players and pre-amplifiers as it is for high current amplifiers. The rectifiers turn on and off at the positive and negative voltage peaks of the AC waveform. These current pulses have high frequency harmonics up to 50 times the frequency of the AC power line. This places a great demand upon the AC power circuit and associated connections to deliver current without significant impedance to the flow.
Placing anything in front of an electronics system that restricts, impedes or slows instantaneous impulse AC power will often noticeably degrade the performance of the system. This is why most electronics manufacturers discourage the use of power conditioners. They understand that traditional low-pass power “conditioners" interfere with instantaneous current flow and interfere with the performance of their carefully engineered power-supplies.
How do you measure current pulses?
Conventional AC power testing methods and equipment are not designed to detect the volume of current delivered during the brief conduction period (milliseconds) and the corresponding impedance during the period of conduction. Multimeters measure voltage and current averaged over a period of one or more AC cycles. Common current probes are too slow to give an accurate reading of current delivery during a single current pulse that has a period of only a few milliseconds.
What is DTCD - dynamic transient current delivery?
DTCD is method of current analysis that measures instantaneous current delivery in the context of a pulsed current draw. In layman’s terms, it is a way of measuring current performance into typical electronic component power supplies. It allows the measurement of pulsed transient current through a variety of AC power products, including: power wiring, outlets, distribution panels, terminals, connectors, power cords and portable power distribution boxes.
Shunyata Research developed a DTCD ANALYZER specifically designed to perform DTCD measurements. The analyzer simulates the pulsed current draw of typical electronic power supplies. It supplies a precision reference voltage to the DUT (device under test) and measures its ability to conduct current during a short gate time (milliseconds). The DTCD ANALYZER provides a read-out of the equivalent current (DTCD-I) that the DUT could deliver in a one second time period. It also calculates the equivalent voltage drop (DTCD-Vd) and corresponding impedance (DTCD-?).
And to save you some time here are some of the most common misconceptions about DTCD graphs.
Why is the amperage in the graphs so high?
You may be thinking that your CD player only pulls about one amp of current and your amplifier only draws about 12 amps. So how can a test be valid that shows the cord pulling hundreds of amps of current?
Power supplies only pull current for about 5% to 10% (or less) of the AC duty cycle. During the conduction period, when the cable is actually conducting current, the instantaneous current could be hundreds of amps, but the longer term average is only one to 20 amps, depending upon the device and the load.
Note: If a power supply is drawing 10 amps of current (as measured by a standard current meter), then the peak currents would be 10 to 20 times higher or 100-200 amps of instantaneous current.
—
It appears from the graph that the standard power cord has voltage drop of more than 50%. How is this possible?
The answer is similar to the answer above. Since the conduction period is short and fast, the cable is presented with an instantaneous change in current. The impedance and inductance of the cable resists the change in current and causes a short term voltage drop across the cable. Of course, there is not a sustained or significant average voltage drop. Otherwise, the equipment wouldn't function.
The DTCD Analyzer uses a source voltage of 30 volts to represent a typical difference voltage between the power supplies storage capacitors and the peak voltage of the line. So, the graph is indicating the amount of voltage drop between the voltage on the capacitors and the line voltage - not the difference between the peak line voltage and ground.
Note the peak of the standard power line(120 volts AC) is about 163 volts (Peak) depending and what the crest factor (1.35 typical) of the power line. What the test shows is that the standard power cable under these test conditions would have a 15 volt drop in the power cable while sourcing 130 amps. While the Venom-3 power cable would only have a 5 volt drop and have the ability to provide almost twice the current 230 amps. – at a third of the cable voltage drop.
Note again that the conduction period is 1/10 to 1/20 of the power line cycle, so peak currents are 10 to 20 times higher than measured RMS currents or rated currents. A power amp at full power can be drawing 10 amps, resulting in peak current draw during the charging period of 100 to 200 amps. If the power amp needs 130 amps of current during the peak charging period, the standard power cable would have a cable voltage drop of 15 volts. This would limit the ability of the input stage of the power amp to fully charge, which effectively would create a relative low line condition as the input stage of the power amp will not be able to fully charge. To put it another way, the input line voltage has been reduced from 120VAC to about 110VAC!
—
Microseconds seems like an unreasonably short period of time to measure current. Why is that?
Since power supplies pull current in pulses and the pulse duration is typically less than 10% of the duty cycle, the conduction period is typically 200-800 microseconds. The time scale for the graphs is about 50 microseconds from beginning to end. Notice that the slope of the measured waveforms levels out and stabilizes within that 50 microsecond timeframe. Therefore, it is unnecessary to display information beyond the 50 microseconds. In other words, the measured differences would be the same even if we extended the time period beyond that shown.
—
If the standard power cord slows current delivery, doesn't it just take a bit longer to fill the storage capacitors?
This is true and explains why the power supply will function within normal average voltage and current requirements. However, that does not mean that there are not audible differences between a cord with better DTCD. A cord with higher instantaneous current delivery will fill the storage capacitors faster. Therefore, the rectifiers are on for a shorter period of time. The longer it takes to fill the storage capacitors means that the peak of the charging waveform has passed while still trying to charge the storage capacitors, thus not able to fully charge the storage capacitors. Also, note the volt drop in the power cable limits the ultimate voltage level that the filter capacitors can be charged to.
A power cable able to supply 300 to 400 amps of charging current will have a much shorter charging time than a cable only able to supply 100 amps. The 100 amp power cable will have voltage drops and resistance that limits its ability to fully charge the input capacitors. As the charging will not be finished before the peak of the power line charging cycle has passed.
This reduces the amount of time that the power supply is in a low impedance, open condition to the power line. When the rectifiers are on, power line noise is more likely to be transmitted through to the power supply.
Some of you have basic misunderstandings about AC power delivery and power rectification specifically. Without some basic knowledge you will never understand the subject.
It is necessary to understand the manner in which power supplies in consumer electronics function. The integrated circuits in consumer electronics require several DC voltages to operate. It is the job of the power supply to convert alternating current (AC) from the wall outlet to direct current (DC) voltages that supply power to the component's electronic circuits.There are basically two types of power supplies: transformer and transformer-less (switched mode) power supplies. Both use rectifiers that are essentially electronic switches that alternately turn on and off in response to the input AC voltage. It is the rectifiers that convert the AC voltage to a pulsating DC voltage.. This voltage is stored and filtered by the power supply storage capacitors that provide the relatively stable DC voltages to the PCBs and integrated circuits.Unlike a light bulb, fan or simple motor, audio/video power supplies do not pull current in a constant or linear fashion. Rather, they pull current in instantaneous pulses as the rectifiers switch on to fill the storage capacitors. This is as true for low current devices such as CD players and pre-amplifiers as it is for high current amplifiers. The rectifiers turn on and off at the positive and negative voltage peaks of the AC waveform. These current pulses have high frequency harmonics up to 50 times the frequency of the AC power line. This places a great demand upon the AC power circuit and associated connections to deliver current without significant impedance to the flow.
Placing anything in front of an electronics system that restricts, impedes or slows instantaneous impulse AC power will often noticeably degrade the performance of the system. This is why most electronics manufacturers discourage the use of power conditioners. They understand that traditional low-pass power “conditioners" interfere with instantaneous current flow and interfere with the performance of their carefully engineered power-supplies.
How do you measure current pulses?
Conventional AC power testing methods and equipment are not designed to detect the volume of current delivered during the brief conduction period (milliseconds) and the corresponding impedance during the period of conduction. Multimeters measure voltage and current averaged over a period of one or more AC cycles. Common current probes are too slow to give an accurate reading of current delivery during a single current pulse that has a period of only a few milliseconds.
What is DTCD - dynamic transient current delivery?
DTCD is method of current analysis that measures instantaneous current delivery in the context of a pulsed current draw. In layman’s terms, it is a way of measuring current performance into typical electronic component power supplies. It allows the measurement of pulsed transient current through a variety of AC power products, including: power wiring, outlets, distribution panels, terminals, connectors, power cords and portable power distribution boxes.
Shunyata Research developed a DTCD ANALYZER specifically designed to perform DTCD measurements. The analyzer simulates the pulsed current draw of typical electronic power supplies. It supplies a precision reference voltage to the DUT (device under test) and measures its ability to conduct current during a short gate time (milliseconds). The DTCD ANALYZER provides a read-out of the equivalent current (DTCD-I) that the DUT could deliver in a one second time period. It also calculates the equivalent voltage drop (DTCD-Vd) and corresponding impedance (DTCD-?).
And to save you some time here are some of the most common misconceptions about DTCD graphs.
Why is the amperage in the graphs so high?
You may be thinking that your CD player only pulls about one amp of current and your amplifier only draws about 12 amps. So how can a test be valid that shows the cord pulling hundreds of amps of current?
Power supplies only pull current for about 5% to 10% (or less) of the AC duty cycle. During the conduction period, when the cable is actually conducting current, the instantaneous current could be hundreds of amps, but the longer term average is only one to 20 amps, depending upon the device and the load.
Note: If a power supply is drawing 10 amps of current (as measured by a standard current meter), then the peak currents would be 10 to 20 times higher or 100-200 amps of instantaneous current.
—
It appears from the graph that the standard power cord has voltage drop of more than 50%. How is this possible?
The answer is similar to the answer above. Since the conduction period is short and fast, the cable is presented with an instantaneous change in current. The impedance and inductance of the cable resists the change in current and causes a short term voltage drop across the cable. Of course, there is not a sustained or significant average voltage drop. Otherwise, the equipment wouldn't function.
The DTCD Analyzer uses a source voltage of 30 volts to represent a typical difference voltage between the power supplies storage capacitors and the peak voltage of the line. So, the graph is indicating the amount of voltage drop between the voltage on the capacitors and the line voltage - not the difference between the peak line voltage and ground.
Note the peak of the standard power line(120 volts AC) is about 163 volts (Peak) depending and what the crest factor (1.35 typical) of the power line. What the test shows is that the standard power cable under these test conditions would have a 15 volt drop in the power cable while sourcing 130 amps. While the Venom-3 power cable would only have a 5 volt drop and have the ability to provide almost twice the current 230 amps. – at a third of the cable voltage drop.
Note again that the conduction period is 1/10 to 1/20 of the power line cycle, so peak currents are 10 to 20 times higher than measured RMS currents or rated currents. A power amp at full power can be drawing 10 amps, resulting in peak current draw during the charging period of 100 to 200 amps. If the power amp needs 130 amps of current during the peak charging period, the standard power cable would have a cable voltage drop of 15 volts. This would limit the ability of the input stage of the power amp to fully charge, which effectively would create a relative low line condition as the input stage of the power amp will not be able to fully charge. To put it another way, the input line voltage has been reduced from 120VAC to about 110VAC!
—
Microseconds seems like an unreasonably short period of time to measure current. Why is that?
Since power supplies pull current in pulses and the pulse duration is typically less than 10% of the duty cycle, the conduction period is typically 200-800 microseconds. The time scale for the graphs is about 50 microseconds from beginning to end. Notice that the slope of the measured waveforms levels out and stabilizes within that 50 microsecond timeframe. Therefore, it is unnecessary to display information beyond the 50 microseconds. In other words, the measured differences would be the same even if we extended the time period beyond that shown.
—
If the standard power cord slows current delivery, doesn't it just take a bit longer to fill the storage capacitors?
This is true and explains why the power supply will function within normal average voltage and current requirements. However, that does not mean that there are not audible differences between a cord with better DTCD. A cord with higher instantaneous current delivery will fill the storage capacitors faster. Therefore, the rectifiers are on for a shorter period of time. The longer it takes to fill the storage capacitors means that the peak of the charging waveform has passed while still trying to charge the storage capacitors, thus not able to fully charge the storage capacitors. Also, note the volt drop in the power cable limits the ultimate voltage level that the filter capacitors can be charged to.
A power cable able to supply 300 to 400 amps of charging current will have a much shorter charging time than a cable only able to supply 100 amps. The 100 amp power cable will have voltage drops and resistance that limits its ability to fully charge the input capacitors. As the charging will not be finished before the peak of the power line charging cycle has passed.
This reduces the amount of time that the power supply is in a low impedance, open condition to the power line. When the rectifiers are on, power line noise is more likely to be transmitted through to the power supply.
No Frantz, we audiophiles do not debate hearing, we debate perception. Unfortunately you seem now interested in whistles, not in the debate of stereo reproduction.
Although the thread debates the burn-in effect, cable burn-in is strongly correlated with the sound characteristics of cables. As we do not have technical explanations that correlate subjective cable sound with measurements, we can not currently hope to have it about burn-in. We can find physical differences in cables due to burn-in, but skeptics will then immediately say the physical effect is too small to have any effect in sound. And yes, I (and many others) will enjoy our well burn-in cables in our systems and share our findings while you will go on trying to justify audio purchases using small science and economics. Fortunately both of us enjoy its preferred view of the hobby ...
(can we move Caelin's sensational post #93 in its own thread under the Shunyata space? Perhaps name it "DTCD explained")
http://www.whatsbestforum.com/showthread.php?15198-Power-Supply-Bandwidth
Cable burn-in, and sensitivity to microphonics, flexing, and so forth is well-known in the RF/mW/mmW (OK, usually waveguides for the latter) and high-resolution measurement world. The sonic differences and need for long burn-in times, not so much, but nobody can really debate what you yourself hear. We could debate whether it is "real" or not but that's a waste of time.
Charge traps, DA, and other effects mean there is a measurable change in cables but the equipment to do so is usually pricey and specialized.
IME power cords matter when the component itself has poor noise rejection and/or there is a ground problem. A change in power cord might impact either of those parameters. It would not need to be an expensive cord, however, but I have no experience with modern audiophile power cords so have no further comments. I have at times wondered why someone hasn't made a little RFI filter in a M/F plug format that would plug into the back of a component, then you plug the stock power cord into that.
Cable burn-in, and sensitivity to microphonics, flexing, and so forth is well-known in the RF/mW/mmW (OK, usually waveguides for the latter) and high-resolution measurement world. The sonic differences and need for long burn-in times, not so much, but nobody can really debate what you yourself hear. We could debate whether it is "real" or not but that's a waste of time.
Charge traps, DA, and other effects mean there is a measurable change in cables but the equipment to do so is usually pricey and specialized.
IME power cords matter when the component itself has poor noise rejection and/or there is a ground problem. A change in power cord might impact either of those parameters. It would not need to be an expensive cord, however, but I have no experience with modern audiophile power cords so have no further comments. I have at times wondered why someone hasn't made a little RFI filter in a M/F plug format that would plug into the back of a component, then you plug the stock power cord into that.
Furutech has several models of exactly that.
I use SurgeX 20 amp power distribution with upgraded parts.
http://www.furutech.com/products/power-distributors-filters/in-line-power-filter-bulk-cables/
http://www.surgex.com/products/rackmount-product-line.html
Shunyata Alpha and Sigma power cords do exactly that, with the added benefit of it being built-in to the cord. Thus you do not encounter the sound degrading DTCD drop that occurs with addon devices.
There is also the MIT Magnum Z Trap and a couple of smaller ones... A Magnum Z Trap helped significantly my phono...
The measurements referred to are very interesting however do they
A) address the question here - burn in, and
B) are they audible? If we can measure differences in the cable, why aren't we also trying to simultaneously measure differences in speaker output? After all, that's what we actually listen to.
My experience with many cables has been, they need time to settle/breakin. No matter what cable it is, it sounds better after a few or more days in the system. Do I need a technical/measurable explanation ? absolutely not. My ears are a great judge of this phenomena.
It would be interesting to see DTCD measurements of a typical home's AC power system. From the power company's big transformer's connections through a fer hundred feet of service entrance cable to the main breaker box and on to the wall outlet ((25 to 100 feet) that is used for the audio set-up.
'cept that if you look into designer bios you'll find quite a few that have come directly from that industry and many more indirectly.
One of my fave cables (no longer in production) were made from copper ribbon transformer windings from USN surplus.
Still my favs!
The ASCC available short-circuit current test, is about the same as measuring power line source impedance. This is an excellent test that could (maybe should) be done on everyone's audio system AC circuit. But measuring power line source impedance doesn't require a special $500 test instrument. This test can be done with alittle Kill-a-Watt meter and a room space heater. Maybe I should write some easy instructions.
But anyway, the ASCC test is a power line frequency test, it in no way resembles the high frequency DTCD test.
But anyway, the ASCC test is a power line frequency test, it in no way resembles the high frequency DTCD test.
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