Theta Introduces The Intrepid Power Amplifier

21-Sep-00

Theta Digital introduced the five-channel Intrepid Power Amplifier at CEDIA EXPO 2000. The Intrepid incorporates several proprietary design concepts introduced in Thetaís Dreadnaught power amplifier, delivering 100 watts per channel into an 8-ohm load (200W into 4 ohms). Each of the Intrepidís channels has single-ended and balanced inputs, and a high-current, dual binding post output connector.Intrepid controls include a front-panel standby mode that mutes and reduces idling current to all channels. The control can also be activated through a remote control jack on the back of the chassis, which would bring a trigger signal from another unit, such as a Casablanca II or Casa Nova. Standby can also be activated by connecting the Intrepidís bi-directional RS-232 port to a computer or other control device, such as one by AMX or Crestron.No Global FeedbackWhile most power amplifiers use global feedback in large proportions, the Intrepid applies local feedback to each of its three amplification stages. Theta incorporated local feedback into the Intrepid because of what it claimed to be its ability to limit unwanted oscillation, reduce distortion, and protect delicate devices from potential damage.A DC-servo for each channel eliminates manual adjustment of DC offset at the amplifier outputs.Intrepid uses a single 1100 VA power transformer and a 35 amp bridge rectifier for all five channels. Unless all five channels are driven to full power, which is not likely to occur in real-world situations, the channels not driven hard effectively lend their portion of the transformer's power to the active channels.The Intrepid uses Wima film capacitors for power supply bypassing, and Nichicon electrolytic capacitors for power supply filtering. Three and four-layer custom-manufactured glass-Epoxy circuit boards with heavy copper plating were specified to accommodate the high currents Intrepid can produce. Amplification Stage TopologyEach amplifier module in the Intrepid consists of three stages. The first stage provides the high-input impedance and initial voltage amplification necessary for driving loudspeakers.The second stage provides additional voltage amplification, and also the current amplification needed to drive the third output stage. The third and final stage delivers the pure current necessary to drive the speaker. The Intrepidís input stage consists of four matched J-FET transistors operating in the zero temperature coefficient region, arranged in a complementary common-source differential amplifier topology using two n-channel and two p-channel FETs. The first stage is directly coupled to the second stage, employing no coupling capacitors or other DC correction circuits.The second stage also consists of four MOSFET transistors, chosen for high current drive capability and superior electrical characteristics. The topology of the second stage uses a complementary common-gate amplifier consisting of two n-channel and two p-channel devices. Theta says that the MOSFETs are hand-selected and matched to assure the best possible performance.The third amplification stage consists of eight high-power, Motorola bipolar output transistors in a fully balanced differential complementary emitter follower configuration, with specialized MOSFET pre-drivers. All output transistors are tested for output power and matched for ideal linearity.The Intrepid is available now at a suggested price of $3,500.  For additional information about Theta Digital, visit www.thetadigital.com.Category: Amplifiers

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