Microchannel plate audio amplifier

A audio amplifier employs microchannel plate for multiplying input electrons to produce output electrons at a rate corresponding to an audio input signal. The MCP may have a segment input source, segmented input and output electrodes or a segmented anode for allowing independent amplification of multiple input channels.

BACKGROUND OF THE INVENTION

This invention pertains to an audio amplifier, and in particular to an audio amplifier employing a microchannel plate (MCP).

Audio amplifiers using vacuum tubes have a characteristic sound which musicians and audiophiles find pleasing. In vacuum tube amplifiers, the input signal becomes distorted, especially when the input is overdriven. The distortion seems to result from clipping and rounding of the input waveform so that the resulting sound is softened. Solid state audio amplifiers do not amplify signals in the same way as tubes and thus do not exhibit the distinctive tube sound. Indeed, solid state devices produce a clean signal which to some sounds unpleasing, sharp and harsh. This seems to be the result of sharp clipping when the amplifier is overdriven.

The availability of high quality tubes for audio amplifiers is limited. Some foreign sources produce relatively inexpensive tubes which do not meet the requirements for high end equipment. Such tubes do not have sufficient consistency to be useful as matched pairs in push/pull amplifier configurations.

Domestically manufactured high quality tubes can be found, but such tubes are expensive. There is even a fairly active market in so called new old stock and used tubes. However, the availability of such tubes from a bygone era is limited.

Despite their inferior performance, transistors are popular because they are less expensive to manufacture and to operate, and they are more robust than tubes. Also, tubes require a hot filament to heat the cathode which consumes substantial energy and is a source of tube failure.

It is also difficult and expensive to build multiple channel tube amplifiers.

It is therefore desirable to provide an audio amplifier which mimics the tube sound and which is robust and has a reasonable cost. It is also desirable to provide equipment which will economically handle multiple channels using a common multichannel tube.

SUMMARY OF THE INVENTION

The present invention is based upon the discovery that a microchannel plate may be employed in as an audio amplifier.

In an exemplary embodiment, the invention comprises an audio amplifier for amplifying audio input signals including a microchannel plate for multiplying input electrons to produce output electrons at a rate corresponding to the input audio signal.

In one embodiment, the amplifier includes means for modulating the microchannel plate with the input signal.

In another embodiment, the amplifier includes means for modulating the input electrons.

In yet another embodiment, the amplifier includes a light responsive source of electrons and means for modulating the light source. The light source may be a coherent light source such as a laser or a focused incoherent light source.

In another embodiment, the invention employs a device in which multiple channels are independently operable for amplifying various inputs and providing separate amplified outputs.

The invention may also be employed to distort the input signal so as to mimic a vacuum tube. As such, the invention may act as a low power preamplifier for driving a downstream power amplifier whereby the power amplifier may simply reproduce the distorted preamplified signal.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1illustrates a simplified audio amplifier employing a microchannel plate (MCP)12having a plurality of channels or apertures14and respective input and output electrodes16and18. A high voltage source20(e.g., 2000v) is coupled to the electrodes16and18as shown. The input electrode16is typically at around 2000 volts and the output electrode18is at or near ground. An electron source, for example a photocathode22, produces source electrons24in response to input illumination26from light source30. The source electrons24, enter the channels14, and by multiple collisions, produce output electrons28at a gain of about 106. The output electrons28are collected by an anode32to produce an output signal34.

In accordance with the invention, a signal source36has outputs38and40coupled across MCP12at respective input electrodes16and18, the signal source36may be an audio signal from any appropriate audio source such as an electrical guitar output, a compact disc player or other electrical instrument. The audio source36modulates the gain of the MCP12such that the output signal34varies in an exemplary range of about 50 V. The output electrodes18may be grounded as shown.

FIG. 2illustrates a microchannel plate audio amplifier50similar to the arrangement ofFIG. 1wherein a similar elements carry the same reference numerals, wherein the gain of the MCP12is controlled by the high voltage source20. A light source52driven by a signal source54at output56causes the light source52to produce modulated output light58which stimulates the photocathode22to produce modulated input electrons60. In accordance with the invention, the input electrons60are produced in greater or lesser quantities depending upon the intensity of the modulated light58. The input electrons60enter the channels14and are amplified by the microchannel plate producing modulated output electrons62at a gain of roughly about 106. The anode30collects the electrons and produces an audio output signal34as shown.

FIG. 3illustrates a multichannel plate audio amplifier70wherein the light28from source30simulates the photocathode22which is modulated by the audio source24. Like the arrangement inFIG. 2, modulated input electrons60are produced which are amplified by the MCP12resulting in modulated output electrons62which are collected by the anode32producing an audio signal on the output34.

FIG. 4illustrates a multichannel, microchannel plate audio amplifier80having a segmented anode82containing anode segments84-1. . .84-N. Each of the anode segments84corresponds to a channel C1-CN. In the exemplary embodiment signal sources72-1. . .72-N modulate light source86-1. . .86-N for each corresponding channel C1-CN to stimulate the photocathode22producing input electrons60-1. . .60-N which are collected as output electrons62-1. . .62-N by the corresponding anode segments84-1. . .84-N resulting in separate outputs32-1. . .32-N. The light source86may be modulated from a modulated laser, one for each channel C1-CN. Alternatively, the input signal may be provided by modulating a segmented photocathode88having segments90-1. . .90-N as shown in FIG.5. Alternatively, the input electrodes16of the microchannel plate12may be segmented into segments96-1. . .96-N forming amplification channels C-1. . . C-N which are aligned with the segmented anode84-1. . .84-N as shown in FIG.6. It is envisioned that the gain of the MCP12may be governed by a uniform high voltage, and the level of the input signal may be increased or decreased to effect the gain. Alternatively, the high voltage on the segments96-1. . .96-N may be separately increased or decreased to provide for separate amplification. As shown inFIG. 7, the high voltage20-1. . .20-N may be separately varied. In accordance with another embodiment of the invention as shown inFIG. 8, the signal source may be the output of an MCP amplifier110according to any of the arrangements illustrated. The MCP may provide a preamplified, softly distorted input signal112to a power amplifier114. The distorted input112may be accurately reproduced at the output118to provide a pleasing tube sound.

FIG. 9illustrates a schematic illustration of an audio amplifier120in accordance with an embodiment to the invention wherein a CD player122providing an audio source is coupled to an audio amplifier124, the output of the audio amplifier124is coupled to the input side126of microchannel plate128. A negative high voltage source130is likewise coupled to the input side to provide a fixed bias. The output side132of the MCP128may be coupled to ground or near ground through a resistor134. The anode136is coupled to an audio amplifier138over a shielded line140. The output of the audio amplifier138may be used to drive a appropriate transducer such as headphones or speakers142. A bias resistor144isolates the anode136from ground as shown. In the embodiment illustrated, input radiation146may be in the form of a beam of energetic particles, e.g. neutrons to activate the MCP128. Other arrangements are also possible.

FIG. 10illustrates a microchannel plate amplifier150in which the microchannel plate152is secured to a heat sink154to cool the active output side156as shown. Such an arrangement allows for active cooling of the microchannel plate to increase the power output of the amplifier.

In another embodiment of the invention, an amplifier160employs an electron source in the form of a microchannel plate162driven to saturation and operating under conditions of self sustained ion regeneration producing active particles164as inputs to microchannel plate12as shown in FIG.11.

While there have been described what are considered to be the preferred embodiments of the present invention, it will be apparent to those skilled in the art that various changes in modification may be made therein without departing from the invention and is intended in the depended claims to cover such variations which fall within the scope of the invention.