Theta Exhibits Multichannel Intrepid Power Amp

Five-Channel, Solid-State, 100-Watt Per Channel Amp Delivers High-End Performance - With No Global Feedback - For Home Theatre

17-Jan-01

Theta Digital, long acclaimed as one of the finest high-end digital audio manufacturers in the world, showcased the new five-channel Intrepid Power Amplifier at the Golden Nugget Hotel during the 2001 International Consumer Electronics Show. Thetaís new fully balanced amplifier offers superior performance, and complements exceptionally well the companyís highly respected Casablanca II Music and Cinema Controller and Casa Nova Digital Preamp/Processor, delivering audiophile sonic quality for multichannel applications. The Intrepid incorporates several proprietary design concepts introduced in Thetaís acclaimed Dreadnaught power amplifier. Delivering a powerful 100 watts/channel into an 8-ohm load (200W into 4 ohms), each of the Intrepidís channels has single-ended and balanced inputs.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, resulting in a clean, pure, fast circuit from input to output. Local feedback was incorporated into the Intrepid because of its ability to limit unwanted oscillation, reduce distortion and protect delicate devices from potential damage. Since local feedback is applied almost immediately back to the input, the Intrepid does not exhibit any of the common by-products of global feedback, such as smearing of the image or harshness and glare at the upper-midrange levels.Intrepid uses a single massive 1100VA power transformer and a 35-amp bridge rectifier for all five channels. This approach ensures that any single channel confronted with a full level signal can harness the entire current capability of the transformer. In Thetaís single-channel power tests, the power transformer did not limit the output power. Unless all five channels are driven to full power, which never occurs in real-world situations, the channels not driven hard effectively lend their portion of the transformer's power to the active channels.High reliability is another chief design criterion of the Intrepid. As a result, every channel of each Intrepid is rigorously tested with a torturous burn-in period before each unit is shipped. In addition, only the highest grade electronic components were chosen for the Intrepid, including Wima film capacitors for power supply bypassing, and Nichicon electrolytic capacitors - known for their superior long-term performance and audio characteristics - 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. A mere 2 volts of input at this stage produces 5 volts of output. The second stage provides additional voltage amplification, and also the current amplification needed to drive the third output stage. With 1.5 volts of input, this stage produces a minimum of 28.5 volts of output, enough to drive an 8-ohm speaker at 100 watts, or a 4-ohm speaker at 200 watts. The third and final stage delivers the pure current necessary to drive the speaker. The Intrepidís input stage consists of four precisely 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. This stage is extremely fast and highly stable with high input impedance. 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. 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. This adds up to a nominal device capability of 128 amps/1600 watts for each 100-watt channel. This ensures safe, reliable operation under all conditions. 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.

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