Our engineers had one simple goal: make the best sounding, most efficient amplifier possible. Their work started with the most basic section of any electronic component, the power supply A design that is able to supply extremely high levels of instantaneous current when needed, while maintaining low impedance throughout. Next they designed a revolutionary new amplifier around our VL Digital Pulse Width Modulation (PWM) technology. Think of it as digitally re-mastering for your entire home theater. In the end, their goal was achieved. The result is a sonically warm, highly efficient home theater powerhouse that is sure to please even the most demanding enthusiast. BACKGROUND To understand what makes the DTA-9.4 unique, it s important to compare its design topology with that of conventional amplifiers. Conventional multi-channel amps are not as efficient, require larger heat sinks, and are bulkier taking up more precious rack space. Conventional Class A/B Amps = 35-40% efficient Integra s Class D Digital Amplifier = 90% efficient Class A/B amps are most efficient when either 100% on or completely off. There are varying lossy modes of operation in between as indicated by the shaded areas below. Class D, or digital, amps on the other hand have only two modes of operation, ON and OFF therefore making them much more efficient than their Class A/B counterparts. Loss Conventional Amplifier Digital Amplifier 1
POWER SUPPLY Low Impedance, High Current Design To provide these benefits, the DTA-9.4 had to have the soul of a world class amplifier a new, originally designed power supply whose low impedance design makes it more efficient and able to quickly react to changes in current demands. To further apply this design approach, there are thick copper bus plates for all power supply feeds even low impedance pressure contact terminations with copper screws are used instead of solder! This low impedance design, combined with a total power supply capacitance of 156,000µF, produces the high current required for those brief, loud passages when all channels are driven at full volume ideal for newer high resolution multi-channel audio formats like DVD-Audio and SACD. Dynamic current consumption during these periods can momentarily reach tens of amperes! With average and even momentary peaks in audio signals, the amplifier s high efficiency keeps current consumption very low (only several Amperes). Amplifier peak current =70A Integrated average current =6.3A Section average current =44.6A Section average current =2.1A 10ms 90ms 10ms This corresponds to an output of 1.6kW or more!! Power Supply Consumption Typical power transformers (torroidal, etc.) operate at the standard power line frequency of 50 or 60Hz. A switching power supply switches at high frequencies (tens of khz) or more. The advantage is that the higher the frequency, the more efficient the transformer and therefore the power supply. Integra s power supply switches at almost 400 khz! At these frequencies, even a small transformer can transmit large amounts of current. Also, because there are fewer coil windings in a smaller transformer there is lower power supply impedance, yielding less current loss. The DTA-9.4 s power supply also features a low negative feedback design for improved performance. 2
Zero Switching Not to be confused with electromagnetically noisy power supplies found in PCs, our original power supply design overcomes the common pitfalls of switching power supplies. All MOSFETs used for switching power supplies have an inherent capacitance associated with them. If not properly monitored this can result in a noisier output. The engineers at Integra have found a way to overcome this potential problem. Wrong Way = Conventional switching supplies do not concern themselves with this capacitance when switching. This results in pulse or switching noise in the output power signal. This is common in other digital amplifiers and also PCs. Integra Way = The DTA-9.4 switches only when the MOSFET s capacitance is zero, resulting in a more stable power supply. Wrong Way Conventional noisy Power supply output Power supply instability Integra Way Switching only takes place at the zero crossing. This all bu t eliminates noise by tracking the MOSFET s charge. This is called zero voltage switching. Zero Switching Output PULSE WIDTH MODULATION There is a common misconception about digital amplifiers that they require the use of A/Ds, D/As, DSPs, etc. The term digital amplifier actually refers to the way the output devices, or amplifiers, operate. In this case, the analog input signal is converted to a digital, amplified output through a process called Pulse Width Modulation (PWM). Analog Input Signal Digital Amplifier s Output 3
PWM Conventional Method Conventional PWM is more of a one-to-one correlation, the change in the analog signal s voltage in a given time period (or cycle ) is translated to a pulse of a certain width. Large voltage values during a cycle yield longer pulses, while smaller changes in voltage result in shorter pulses. A long pulse followed directly by a short pulse (or vice versa) indicates a high frequency. The problem with this standard PWM implementation is that signals which have been converted from digital to analog will have what is known as pulse noise riding on top of the audio signal. This includes sources such as DVD, CD, or any signal that passes through processing such as THX, Dolby or DTS. In more conventional Class A/B amplifiers this noise is simply amplified along with the signal. With digital amps however, the pulse noise results in a phase shift in the digital output. The Pulse Width Modulated signal carries phase inaccuracies created by pulse noise in the original signal (see figure below). PWM + VL Digital = Integra Exclusive Other digital amplifier designs which attempted to address the challenges listed above did so, but with an unacceptable sacrifice in tonal quality. Using VL Digital for PWM during digital conversion/amplification, the DTA-9.4 maintains the sonic advantages of a conventional amp, but with higher efficiency and a smaller footprint. In much the same manner as VLSC (Vector Linear Shaping Circuitry) in our recent DACs, VL Digital smooths out pulse noise in the analog signal using a vector generator. This integral method translates the waveform s energy during the brief sample cycle into the PWM waveform (the integral of the signal yields the area under the curve, also known as energy). Think of it as digital re-mastering for all audio sources! By looking at the average energy in a given cycle, phase error is greatly reduced. Using VL Digital, Pulse Width Modulated signal is free from phase inaccuracies created by pulse noise in the original signal. Pulse noise Pulse noise Comparison signal (triangular wave) Input signal Input signal Phase Error No Phase Error Conventional PWM Only Integra PWM + VL Digital 4
BUILD QUALITY High Quality, Gold-plated Speaker Terminals This simple, yet very important innovation accepts heavy gauge speaker wire, thick spade connectors, and dual banana plugs. This extends the low impedance design approach all the way down to the speaker terminals! This creates a larger pipe through which to push the audio signal, and provides a purer signal path yielding better sound quality. Seven channel discrete topology Each of the seven independent amplifier blocks feature 240W into 4Ω per channel (120W into 8Ω), and independent power supply filtering to provide noise-free power. For the highest quality connection to your processor each has a gold-plated unbalanced input that is machined from a solid brass billet, and a gold-plated locking balanced XLR input. DESIGN SUMMARY Stable high-current power supply for on-demand peaks with minimal distortion. Efficient, modular design allows seven high-current/high-power channels in a single standard-size chassis. Low-Impedance design is capable of handling the most demanding speaker loads. All the sonic detail and depth of much more expensive designs, in a smaller form factor. - Wide-range frequency response (10Hz-60kHz) High efficiency means cooler operation for better operational stability and long term reliability. Overbuilt approach not only contributes to better sound, but to longer life. 5