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Following are a series of frequently asked questions related to Dynamic Transient Current Delivery. The answers provide insights into the critical role DTCD plays in the performance of professional and consumer audio-video systems. Please send questions about DTCD to us at cservice@shunyata.com. We will post replies to all questions of general importance in the FAQ section.
What kind of claims are you making regarding DTCD? Are you saying DTCD is the ONLY design parameter that affects power device performance? Absolutely and categorically not! There are many design parameters that affect performance. We like to use an analogy to speaker design. There are many design parameters for speakers including the type of drivers, crossovers and cabinet materials. There are also several speaker related measurements such as frequency response, phase response, group delay and many others. Saying that DTCD is the only design parameter for power devices is like saying the only important parameter for speakers is frequency response. DTCD measurements are analogous to frequency response for speakers in that they are fundamentally important aspect. Instantaneous current delivery for power devices is critical to their proper operation. If a power device has poor DTCD performance it will likely not perform well just as a speaker with severe frequency response anomalies would perform poorly. If the design parameters for power devices were arranged in a hierarchical, pyramidal chart -- DTCD would be at the base of the pyramid. If two power cords had similar DTCD measurements, one could be significantly superior in performance to the other based upon other design parameters higher up the pyramid. However, a power cord with significantly inferior DTCD will almost certainly perform poorly by comparison. Top
(These questions have been grouped together because they are similar. They all come under the, "Isn't it unfair that you used xxxxx.") What is the gauge of the standard black cord used in the comparison charts? What is the type of connector used on the standard black cord? What type of insulation is used on the standard black cord? Were the connections on the standard black cord crimped or soldered? For more than 10 years Shunyata Reseach has been saying that all of the following power device related materials, specifications and procedures make a difference in audible and visual performance. WIRE
Are there some standard black OEM power cords that may have good DTCD performance? There are only a handful of commodity OEM power cord suppliers. We have more than 20 different models and brands that we have tested with the DTCD Analyzer. These range from 18 gauge models to 12 gauge models with differing connector types depending upon the manufacturer. There is a wide range of DTCD performance results, however none of them outperform a Shunyata Research Venom-3 power cable. Most of them have significant DTCD degradation -- however there are a few that have tested quite good. The problem for the consumer is, how do you know which ones are the rare good ones and which are not. They do not come with DTCD index ratings so that you can make an informed choice. Just because a power cord is a standard cord or that it is black doesn't necessarily make it bad. We could have made the Venom-3 cord in a black color and it could have been OEM'd by a variety of audio manufacturers. It would still have excellent DTCD performance. So, we are not damning a whole segment of products simply because they are "standard". Interestingly, the cables that tested well seem to have been manufactured with more care and attention to detail. They also have higher wholesale costs than the more "commodity priced" models. Which one do you think are most likely shipped in the box with your new CD player? Top
Why should a power cord, outlet, or their influence on DTCD matter when "miles and miles of wire" precede the system? Perhaps the most common misconception about electronics and electrical systems is the belief that components lie at the end-point of a long electrical pathway. Given the distances of ordinary wire that precede home or studio systems, many believe there is little value in using top quality power cords or similar high-performance AC components at the end of this electrical chain. The only problem with that concept is that it represents a false assumption based on what is commonly referred to as the garden-hose analogy. Power is not delivered to electronics like water through a hose and components do not sit at the end of a long distance electrical delivery hose. All power supplies lay between two poles of alternating current -- the hot and neutral. Once powered on, components represent the beginning of an electrical interaction, not an end point. They are essentially tapping into a vast reservoir of current. Components that are in close electrical proximity to one another are dramatically affected by neighboring components electrical emissions including EMI, RFI and conducted electrical noise. Electronics have long proven to be far more affected by noise generated within the system -- through shared AC distribution, component radiated EMI or the back wave of power-supply energy, than they are by noise generated hundreds of feet much less miles away. In brief, electronics are minimally affected by electrical conditions that exist outside their immediate environment (with the exception of voltage fluctuations which are tightly regulated by the power company). Let's define the local electrical environment as that which exists between the home's AC electrical panel and the home entertainment system. Beginning at the electrical panel, the importance and gauge of the in-wall wiring, splice connections, terminations, and outlets increases dramatically as the AC signal nears its interface point with the power supplies of electronics. By this measure, the power cord connecting a component to its power source is not the last six feet of an electrical hose. At the point of connection between a component and power source, the power cord becomes a functional extension of the power supply itself. In terms of AC delivery, it is this local electrical network of primary connections, terminations, wiring and outlets that will have the greatest potential impact on the performance capability of recording, mastering and consumer A/V systems. These simple tenets are based on the near-field sensitivity and functionality of all A/V components. Top
What Elements can limit DTCD to components? Electrical circuit elements that affect DTCD include the integrity of the electronics most proximal contact junctions, terminations and connections. Power cabling, power conditioners and outlets that lead to the system have the greatest opportunity to impact performance due to their electrical proximity. Any in-line element that adds inductive properties (defined as elements that resist changes in current) or corrupts junction-to-junction conduction will degrade DTCD and will reveal itself as audible or visual degradation. Cheap or worn outlets, poor quality power cords, computer power strips or low-pass power conditioners can have a singular or cumulative effect that will severely degrade DTCD. These resistive properties can radically affect the audio and video performance of any professional or entertainment system. An example of an adverse relationship between DTCD electrical performance and sound would be to place a large transformer or coil in line between a high-current draw amplifier and the wall outlet. The result will be a clearly audible compression of dynamic peaks, losses in phase coherence and a muting of the critical timing and first order harmonic elements in sound. This same effect will also appear when adding multiple junctions such as AC plug adaptors, 3-2 prong AC jumpers in series. AC is still getting from A-B but the impulse current is being dramatically impeded and the voltage losses begin to mount until they are easy to discern. Top
What are some advantages of an all DTCD AC system? Consistent Performance The DTCD measurements demonstrate the sensitivity of A/V electronics power supplies to their proximal electrical environment. By maximizing connection quality and minimizing in-line impedance, the power supplies of electronics will perform exactly as their manufacturer intended. The simpler, cleaner and more highly conductive the AC path becomes, generally the more favorable and consistent the performance results will be. Perhaps the greatest attribute of any AC system designed for DTCD is its ability to deliver consistently improved performance across all categories of electronics whether tube, solid-state, analog or digital. The same consistency applies to systems designated for playback, recording, mastering or film. Simplified AC systems have been out-performing needlessly complex and over-engineered delivery devices for years in all manner of contexts. Optimal Peak Current Delivery This is the defining element of DTCD and should be the foundation of all AC-delivery systems that support A/V electronics. There are many other parameters of electrical design that affect performance but instantaneous current delivery capability is a foundational aspect of any top AC system. Amplifiers and recording panels may be the top beneficiary of a DTCD designed system but all electronics will benefit from top-quality connections and direct-current simplicity. No amount of noise-suppression or filtration can replace or cover up a sub-standard base line of Dynamic Transient Current Delivery. Superior Noise Dissipation All passive AC components that possess measurably low impedance and optimal DTCD characteristics will dissipate and release noise energy in less time than a similar product with high-measurable impedance. As shown in the measurement graph, after a pulsed transient of current courses through a power cord, there will be residual noise energy left behind. How quickly that noise energy dissipates is relevant to component performance because this impulse delivery is recurring 120 times per second, leaving high-frequency harmonics in its wake. Couple these measurements with the knowledge that power supplies themselves generate a significant back-wave of noise energy and the critical importance of low-inductance power cords and outlets becomes clear. Top
I have evaluated several aftermarket power cords in my system and cannot hear a difference. Why? Assuming the power cords tested were well made and served the purpose of reasonable DTCD then several common variables are likely playing a role in a null result. DTCD is a foundational power delivery concept, not a power cord or an outlet -- not a make or a model. Replacing one stock power cord with a better aftermarket model on a CD player, pre-amp or amp is analogous to pouring one part clean water into four parts dirty water -- the "water" is still dirty. To get a clear idea of the capability of improved AC cords, it important to replace ALL of the cables that have low DTCD and are impeding current delivery. The integrity of the rest of local AC network should also be evaluated. One loose connection or significantly degraded AC contact point can obscure benefits elsewhere. The other major factor to consider in evaluating the potential advantages of a measurably better power cord is the balance of the AC system. Systems that use massive low-pass filters will automatically be less sensitive to the (low-impedance to peak current) advantages of top quality outlets or power cords. Systems that use transformers, chokes, coils, voltage stabilizers and AC "networks" represent the opposite end of the spectrum from DTCD in terms of engineering and philosophy. It never benefits a pro or consumer A/V system to mix and match varying AC perspectives in the same system. Most often, competing approaches will unnecessarily complicate the system and make results of future component or power-system evaluations impossible to predict. If the evaluation context is within a replay system then the system and room variables also come into play in how apparent a single or dual power cord change might be. Top
What are the priorities when installing an electrical system for optimum DTCD? Creating the ideal DTCD support for A/V electronics should prioritize a minimalist approach to AC delivery that emphasizes the use of dedicated lines, top quality outlets, DTCD tested power cords and low impedance passive power-distribution. The process can start by making sure all AC contacts and connections are tight, clean and secure. Given that the primary AC connection to the electrical grid is a component power cord, replacing stock power cords with competently designed low-inductance aftermarket AC cords can be a reasonable first step. Consider brands that have explainable science and a history of professional, industry and commercial success. Replace cheap wall outlets and power-strips with better commercial grade models. These items do not need to be extravagant or expensive. If the power cords, outlets or distributors are well chosen, they can provide measurable and subjective benefits over commodity made brands and models. Whenever possible, consider adding a dedicated line for the system or even better, two lines on for source equipment and an additional AC line for amplifiers. Have an electrician tighten the breaker contacts at the AC panel and the system's wire-to-wall outlets since they tend to loosen over time. Install over-rated AC elements such as a 20A breaker and 10-AWG in-wall wiring when possible. **Refer to Shunyata Research Electrical System Concepts for more details.** Top
Is DTCD the most important or only factor to consider in building the best AC distribution system? There are of course other factors involved in building an exceptional power distribution system for professional and consumer A/V systems. DTCD represents the foundation, or base of the pyramid that has to be in place for the other qualities and elements of an AC system to be significant. If there is degradation to DTCD for instantaneous current then the benefits of noise isolating properties will be all but wasted. The other vital aspects of power-system design that are important to address are component-to-component interference (CCI), system protection and external grid-borne noise isolation. Please see our Electrical System Concepts for details. These sections go into detail regarding the importance of managing system generated noise and the best methods of protection from surges, spikes and grid borne noise -- all without altering DTCD performance! Top
Is DTCD expensive to implement compared to other approaches to AC delivery? No, in fact of all the approaches to AC distribution, refining a system for optimal DTCD performance should be the least expensive. Replacing poor quality wall outlets with commercial grade models can cost less than $25 each. Replacing stock power cords with audio grade, low-impedance, RFI shielded models can cost less than $100 each. For those capable of installing dedicated lines to separate high current from low current electronics it's a matter of an electrician's time, labor and material. Installing a quality passive power distributor can cost $500 or less. Approaching the AC as a system and optimizing DTCD within that system is far more cost effective than simply buying a mega bucks power conditioner. Look for the elements in the system that may be a weak link to delivering instantaneous current and replace it. There really are two completely different routes to take in building an AC system for sound, film and playback components. One espouses buying boxes that actively process or regenerate the AC waveform in order to "fix" what's supposed to be wrong with it. The DTCD approach is all about applying AC refinements system wide that maximize current flow, passively isolates components from noise and preserves the relationship to AC that the manufacturers of your electronics intended. DTCD Technical Points What equipment was used for the testing? - Tektronix 4-channel 100Mhz bandwidth, 1Ghz sample rate, data-storage oscilloscope - DTCD Analyzer 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? Read the DCTD Development white paper. 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 the power supply. Notice the residual noise graphs of the two power cords. The standard power cord stores more energy which is radiated back into the power supply at the end of every rectification cycle. This happens over and over again 120 times per seconds. The noise generated by the standard cord is significantly higher and is sustained longer than the Venom-3. Related to this is the fact that the reduced impedance of the Venom-3 allows noise generated by the power supply to more easily migrate away from the power supply instead of being reflected back. As an aside, many of the European countries are mandating that consumer electronics have "power correction circuits" built into them to reduce power line harmonics. These circuits use boost and chopper circuits that increase the number and frequency of current pulses per power cycle. This will make DTCD measurements even more significant in the future. The additional impedance of the standard power cord can significantly degrade power factor efficiencies. This is quite a complex subject and itself represents a very significant white paper topic that we may address. Top |
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2002 - 2012 Shunyata Research. All Rights Reserved.
There are audible and visual performance differences between power cords (and other AC power products).
Some of these differences can be directly attributable to Dynamic Transient Current Delivery.
We have developed a device and methodology to measure power products using the DTCD Analyzer.