Abstract: A novel single-ended screen-regulated cathode-follower output topology for implementing vacuum-tube audio power amplifiers for the reproduction of high-fidelity music with minimal audible distortion. The screen regulation substantially reduces the distortions and noise in the current fed to the output tube by a non-regulated power supply. The noise and distortion of the power supply voltage are thereby prevented from intermodulating with and distorting the music signal.

Abstract: A novel single-ended screen-regulated cathode-follower output topology for implementing vacuum-tube audio power amplifiers for the reproduction of high-fidelity music with minimal audible distortion. The screen regulation substantially reduces the distortions and noise in the current fed to the output tube by a non-regulated power supply. The noise and distortion of the power supply voltage are thereby prevented from intermodulating with and distorting the music signal.

Abstract: A multithreading computer system provides concurrent asynchronous preemptive time-sliced execution of a plurality of threads of instructions located within the same software program. A clock or timer periodically activates the interrupt operation of the central processor. Each interrupt preempts an executing thread after the thread has executed for a brief timeslice during which the thread may have performed only a portion of its task. Control of the processor is thereby taken away from the preempted thread, and control then passes to an interrupt service routine which then passes control to another thread to invoke the latter for execution during the next timeslice. Control is thereafter returned to the preempted thread to enable the latter to resume execution at the point where it was previously interrupted. Control of the processor is thus transferred repeatedly back and forth between the threads so rapidly that the threads are run substantially simultaneously.

Abstract: A multithreading computer system for the preemptive asynchronous concurrent execution of a plurality of instruction threads of a multithreaded application program. As an illustrative example of one of the many uses of the invention, the disclosed application program comprises a compiler thread and an editor thread. The compiler processes the source code while the programmer edits the source code at the keyboard. An interrupt sevice routine repeatedly activates the editor thread to provide a preemptive asynchronous editing process for either entry of new source code or modification of the previously entered code, while the compiler thread concurrently processes the source code during the time intervals between keystrokes. The interrupt service routine may be activated either by a keyboard interrupt or periodically by a clock at predetermined time intervals.

Abstract: A nonslewing amplifier comprises two push-pull voltage-amplification stages each having a complementary pair of grounded-emitter transistors. The first stage has a load impedance connected to each of the transistor collectors. A pair of feedback compensation capacitors are each connected from the collector output to the base input of a respective transistor of the second stage. When a large fast signal causes slewing in one half of these stages due to insufficient current from the respective load impedance to charge the associated compensation capacitor at the rate required by the signal, the transistor in the other half of the first stage draws enough current to discharge the other compensation capacitor at a rate fast enough to transmit an undistorted signal to the second stage where it is amplified and transmitted to the following drive stage. Slew limiting and transient intermodulation distortion are thereby avoided.

Abstract: The disclosed amplifier comprises a high-frequency power output stage for current amplification of the high-frequency signals and a separate low-frequency power output stage for current amplification of the low-frequency signals. Reactive coupling means, including either inductors or a capacitor or both, together with resistors, coact with the two output stages to provide a novel crossover circuit to transmit high-frequency signal to the amplifier output terminal and low-frequency signals to the inputs of the low-frequency output stage to drive the latter. Each output stage is disclosed as having its own power supply. Each output stage may thus be implemented with devices optimized for its respective frequency range, intermodulation distortion is substantially reduced, and similar benefits accrue in the design of the separate power supplies.

Abstract: The disclosed amplifier comprises a MOSFET output stage biased for Class A operation and a bipolar current amplification stage biased for Class C operation. The latter stage is normally cut off, and at low power output levels the entire output signal current is provided by the output stage. Current sensing resistors measure the magnitude of the output current and apply to the base-emitter junctions of the current amplification transistors a bias voltage proportional to the output current. When this current reaches a predetermined magnitude the current amplification stage becomes active so as to provide additional output signal current in parallel with that provided by the output stage. As a result at higher power output levels the output stage sees a load impedance much higher than that of the loudspeaker system and therefore has a flatter load-line which maintains its operating point in the active region.

Abstract: A transistor power amplifier is provided with direct-current-coupling between stages and to the loudspeaker. The output stage is push-pull single-ended and includes two transistors connected in series at a midpoint of the stage. A split power supply has a center-tap connected to one output terminal and the other output terminal is connected to said output stage midpoint. Amplification and drive stages are direct-current-coupled in cascade to the output stage. A direct-current negative feedback network extends from the output stage to an amplification stage to maintain the output terminals at substantially the same quiescent potential to prevent direct-current flow through the voice-coil of the loudspeaker.