The DMA-200S High Resolution Amplifier




Like the innovative DMA-360 Reference Amplifier, the DMA-200S utilizes Spectral's unique "Focused Power" output section design with powerful ultra-fast Mega FET devices. Each device, having vacuum tube like operating character, is energized from its own dedicated high energy storage capacitor, rectifier, and individually powered from an isolated ultra-low coupled transformer winding. Individual Teflon bias trimmers are used to calibrate each output device separately. Groups of these individual output device/power supply circuits utilize field folding construction and electronic shielding to further impede propagation of stray interference. The resulting "Focused Array" of individual isolated output sections performs as one with virtually no cross-coupling and energy storage artifacts reflecting between output devices. During extreme program dynamics, this arrangement can launch an instantaneous high current drive of over 60 amps per channel to the most sophisticated loudspeakers with assured precision waveform tracing. Gone are performance damaging magnetic and electrical field propagation problems of conventional multiple device heavy construction. Without stray radiation, critical small signal paths within the DMA-200S and other sound system components can perform with lowest distortion and settle to signal extinction in microseconds. Hence, the DMA-200S works with power and speed yet behaves inert to other electronic parts of the system. Reproduction is highly articulate and resolving yet has all the powerful unlimited character of the best very high power amplifier designs, giving little suggestion of its actual 180-watt-per-channel output specification.



The Focused Power output section of the DMA-200S is only one of the many Spectral innovations designed to create the ultimate in amplifier control and resolution. A unique transformer architecture supports the critical requirements for lowest noise and high power capability of the powered output section array.
In traditional high-end power amplifiers, output transformers are located away from active amplifier circuitry for purposes of noise isolation and construction ease. This virtually universal method extracts a significant sonic price, however, because of the speed and regulation losses which are imposed by the long power supply wiring harness. In addition, the EMI and noise which radiate from the supply harness invariably contaminate sensitive low level circuitry by noise modulating the musical signal. Spectral engineers have long recognized the problems associated with power supply noise contamination and have proposed a unique solution in the DMA-200S High Resolution Amplifier. The Power Vault electromagnetic field containment system virtually eliminates EMI radiation to the amplifier signal path circuitry as well as power and regulation losses through the traditional power supply harness.
The architecture starts with Spectral's elaborate high performance custom power supply transformers. These unique designs are the result of years of research and development to maximize isolation and regulation. Each transformer features individually isolated windings to support each individual output transistor in the amplifier output section, a premium technique shared only with the Spectral DMA-360 Reference Amplifier. The twin power transformers are mounted between massive machined mounting plates for damping and resonance control. The combined 38 lb. Transformer structure is then mounted on a constrained rubber floating suspension system employing multiple compliances similar to a fine turntable suspension. The finished transformer assembly is then suspended inside an EMI, RFI tight welded aluminum containment box located directly beneath the DMA-200S output section. The resulting transformer Power Vault containment system results in an uncompromising solution to the universal power supply noise problem. The high-current power transformers are now intimately sited next to their own high-current output devices with extraordinary noise isolation. The high-speed driver circuitry of the DMA-200S operates in a pristine environment free of the noise radiation and phantom signals which plague other power amplifiers. Dynamic range limitations are removed with a sonic clarity and quietude which is palpable.



Small signal circuitry is based on Spectral's proven discrete circuit, multiple cascode, double push-pull FET technology. Premium silicon array construction, similar to circuitry in the DMC-30 Reference Preamplifier, is applied to the DMA-200S to achieve enormous internal dynamic range capability. This reserve is linear class A with many times greater dynamic capability than program demands. It allows high current drive for quick controlled response from the large output FET's as well as isolation from their internal electronic activity. Unhindered by interferences and slow cumbersome response of conventional practice, these parts operate with unyielding control and exacting precision. Reproduction is clean, effortless and highly holographic.
Audio amplification paths through the DMA-200S are direct, inherently linear and simple. These minimalist configurations have always sounded and measured best but normally become ponderous and overburdened when protection and support functions are added. The DMA-200S takes a different route to solve the sonic problems of amplifier protection circuitry. To maintain the pristine signal path, a sophisticated analog computing ancillary system is thermal and opto coupled within the amplifier. This "hands-off" operational management system observes device loading and power dissipation as well as speaker damaging out of range signals. It takes control without circuitous cross interfering connections to electronics in the signal path, leaving the musical signal pure and totally untouched.



Improvements in high-current FET technology, high-speed amplifier topologies and new protection systems are combined in the DMA-200S High Resolution amplifier to successfully advance the art of amplifier design. Until now, amplifiers could not offer both powerful speaker control capability and the sonic transparency and life possible only with high-speed, fast settling circuitry. Breakthrough circuits backed by Spectral experience have now brought together the necessary combination of speed, accuracy, control and stealth. The DMA-200S High Resolution Amplifier advances the Spectral tradition for musical resolution and sonic holography. Although of moderate size, the DMA-200S offers remarkable sonic sophistication and drive precision for the most demanding system applications.


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