What is DTCD?
DTCD PROVIDES FOUR TYPES OF MEASUREMENTS:
This measurement represents the quantity of instantaneous current available through a specified power device or circuit. Measured in amperes.
Represents the impedance to transient current during the conduction period.
Represents the voltage drop across the device during the conduction period.
Represents differences in stored residual noise energy.
To understand the relevance of this measurement it is necessary to have a basic understanding of the unique manner in which power supplies in audio and video electronics function.
There are essentially two types of power supplies used in audio and video related electronics: transformer based or digital (switched mode). Both use rectifiers that behave like electronic switches. These rectifiers 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 -- which is in turn conveyed to components storage capacitors. The effectiveness and timing of this process is undeniably critical to each components performance.
Unlike a light bulb, fan or simple motor, audio/video power supplies do not pull current in a steady or linear fashion. Rather, they pull current sharply, 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. This places great demand upon the integrity of the associated AC power circuit and connections to deliver instantaneous current without significant impedance to the flow.
Placing anything in front of electronics systems that can measurably restrict, impede or slow instantaneous current can noticeably degrade critical aspects of A/V system performance. This is not new information. For years, electronics manufacturers have discouraged the use of low-pass power filters. They understand that traditional "conditioners" interfere with instantaneous current flow and will degrade the performance of their carefully designed power-supplies.
Is DTCD different than conventional measurements?
Conventional AC power testing methods and equipment are not designed to detect the volume of current delivered during the brief conduction period (microseconds) or the corresponding impedance during the period of conduction. Multi-meters 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 microseconds.
The DTCD ANALYZER is unique in its ability to generate dynamic transients of current and measure the effects in-line devices have on the transmission of impulse current. This measurement is directly related to the performance and primary function of A/V power supplies.
How was DTCD developed?
Since its inception, Shunyata Research has pursued every avenue of scientific measure as a means of perfecting its own designs. Shunyata uses the most sophisticated measurement equipment in the industry including spectrum analyzers, power analyzers, high bandwidth scopes, impedance analyzers, high voltage testers, electromagnetic and static field meters and a host of other measurement equipment. However, even these sophisticated devices could not correlate an objective measurement to the thousands of reports claiming profound results when changing a power cord or a wall outlet in an A/V system. To measure items that are essentially wires and contacts, it became clear that a new approach would be needed to develop an effective measurement methodology.
Caelin Gabriel came up with the concept for a device that would simulate the virtual constant voltage source of the power grid while emulating the on-off impulse behavior typical power supplies. This measurement device could deliver the micro-second impulses commonly drawn by rectifiers while measuring key electrical parameters of in-line devices such as outlets, power cords and power strips. Gabriel shared the concept for this device with a former lead designer, from a well known test equipment manufacturer, who refined the concept and created the high-current, precision circuits required to for the DTCD ANALYZER. The measurements relevance to the performance of A/V systems is based on the existing principles and method of electrical delivery to A/V power supplies. The DTCD Analyzer will continue to prove its value by creating clear objective guidelines for creating the foundation of an ideal electrical distribution system for A/V systems.
How is DTCD measured?
The DTCD ANALYZER is specifically designed to simulate 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 (microseconds). 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-). The DTCD Analyzer is also capable of measuring differences in stored noise energy within any device after the reference voltage is turned off.
Does DTCD affect audio or video performance?
There are significant measurable DTCD differences between various power cords and power distribution devices. In many cases, the differences can measure as high as 50%-100% between similar products -- which by any standard is a profound measured difference.
Comparative subjective listening tests have been conducted spanning several years, under controlled conditions using blind and double blind tests that repeatedly confirm the connection between system performance and measurable DTCD. These results will be published along with more detailed information in a series of supporting FAQ documents.
For years, thousands of recording professionals and A/V enthusiasts have reported unmistakable auditory, or in the case of film, visible differences when evaluating after-market power-cords, outlets and power distributors. The DTCD results affirm that many of these reports could be easily validated through simple DTCD measurement. Some listening results could be predicted given a dramatic difference in the DTCD measurement of AC components such as outlets or power cords.
Important Note: DTCD is NOT the only design parameter that separates the performance of power products. However, due to the foundational nature of current and voltage integrity it is clear that a product will have severely impaired performance if it has significantly low or diminished DTCD.
Why DTCD is important
The measurement results highlight the critical role near-field electrical components play in the performance of recording and home entertainment systems. Refining an AC system to maximize conductance and minimize impedance will deliver consistent, objectively superior performance in any audio-video based electronics system. The DTCD results represent an electrical foundation from which all professional and entertainment systems can benefit, no matter how different the electronics or goals of the system may be.
The DTCD measurements are directly related to the principal function of component power supplies. They demonstrate objective differences that favor electrical systems engineered for maximum peak-current delivery. There are other important design considerations that affect AC system performance but none are so fundamental to the primary role of the power supply. These results represent a solid, empirical foundation for continued research into the relationship between AC delivery and pro-recording or A/V system performance.