Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-10-27
2004-07-20
Cuneo, Kammie (Department: 2827)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S760000
Reexamination Certificate
active
06765802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains generally to devices, assemblies and systems for sound reproduction and/or recording, and more particularly to an audio sound apparatus which provides enhanced sound quality by maintaining one or more solid-state components at elevated temperature during sound reproduction.
2. Description of the Background Art
Before the mid-1960s, vacuum tubes were the technology used for audio amplification. Various tubes were developed for radio, television, radar, RF power, audio and specialized applications. Over several decades of design, with a limited selection of tubes, a few standard designs for audio amplification evolved. Tube power amplifiers consisted typically of a preamplifier stage to increase the voltage signal, and an output stage to provide power amplification. The output impedance of a tube amplifier without any feedback or transformers in the circuit is limited by the characteristics of tube technology to tens or hundreds of ohms. Output transformers are usually used to lower this output impedance to provide good power transfer to low impedance loads, such as loudspeakers.
The semiconductor (transistor) revolution provided immediate advantages to the power amplifier industry over existing vacuum tube systems. Semiconductor systems are small, reliable, and they dissipate far less heat than vacuum tubes. Furthermore, transistors can be low voltage devices with low inherent impedances that eliminate the need for audio output transformers. This greatly reduces potential cost, and eliminates the distortion effects and bandwidth limitations of the transformer. The majority of systems and devices which at one-time relied on vacuum tubes have been converted to semiconductors, leaving only a few vacuum tube types manufactured and in regular use, predominantly in the high-end audio field.
Despite 35 years of transistor technology, and the apparently simple task of amplifier design, there is no standardization within the industry. Audio experts have come to recognize that all audio devices have inherent distortions to which the human ear is remarkably sensitive. The conventional measures of total harmonic distortion (THD) and frequency response have proven to be inadequate in comparing one amplifier to another.
Vacuum tube systems, with their obvious drawbacks of inefficiency, heat, unreliability, size, and high impedance, still command a strong presence in the high-end audio industry. Many listeners find vacuum tube amplifiers to be more “transparent” than semiconductor systems, meaning the vacuum tube systems are less prone to the type of semiconductor distortions that change the original characteristics of the music signal. The survival of the vacuum tube amplifier defies the logic of conventional engineering measurements to this day.
For the past two decades, designers of high-end audio equipment have focused on the task of trying to get solid-state (transistor) amplifiers to sound like vacuum tube amplifiers. These efforts have usually focused on the measurable distortion characteristics found in many of the older vacuum tube amplifiers. The human ear finds even-order harmonics to be inherently of a musical nature, and some favored tube amplifiers are rich in these harmonics. Despite these efforts, no designer has yet succeeded in duplicating the quality of sound generated by tube amplifiers, as evidenced by the wide variety of designs and systems that are to be found in the current market, and the continued survival of vacuum-tube products. The high-end audio music market has not shifted to one type of transistor circuitry as the best design.
The main focus of research for the audio industry has been directed toward the circuitry. Presently, most high-end manufacturers of solid-state amplifiers recommend that their equipment should be “warmed up” before critical listening, but none of the makers have actually demonstrated, or even realized, that the sound quality is directly related to the thermal heating of solid-state components. The recommendation to “warm up” an audio system may originate from the classical vacuum tube systems in which “warm-up” was necessary for operation. Most manufacturers need to keep the external case temperatures low for safety and reliability of audio appliances, and strive to keep the semiconductors below 60° C.
Class A amplifiers have become popular in recent years due to their enhanced sound quality. The Class A amplifiers are designed for high output-device currents which improve linearity since the devices are always conducting. In addition to increasing measured linearity, Class A amplifiers also elevate temperatures of the output devices, though this is not the stated purpose of the increased current. The consensus is that the higher the bias currents, as in the class A amplifiers, the better the sound, since the circuit becomes more linear. As the current is increased in the output stage to increase this linearity, every effort is made to keep the output device temperature low with large heatsinks. Despite these improvements, they have not enabled solid-state audio systems to obtain the same “transparency” found in vacuum tube systems. Such Class A amplifiers fail to achieve this goal because they do not raise the temperature of the output devices sufficiently, and make no attempt to raise the temperature of the other semiconductor devices in the amplifier, such as those found in the preamplifier stage.
Some of the best available amplifiers have become passive heat managers. They are provided in very large packages that do maintain an elevated temperature. Present amplifiers typically maintain the external heatsink temperature at no more than 60° C., and the junction temperature at no more than approximately 70° C. The external heatsink temperature must stay low for safety.
A few amplifiers contain thermal monitoring or thermal control devices to determine the temperature of output devices. These temperature monitoring devices are utilized to ensure that the components do not overheat and therefore are believed to contribute to system reliability. Other thermal control devices are designed to compensate for varying bias current caused by fluctuating temperature to maintain the signal gain relatively constant.
The present trend in the audio industry is to restrict temperatures of power devices. External heatsinks are restricted to about 65° C. Celsius or lower in order to keep the product safe to touch. Low thermal impedances are maintained to keep the output devices as close to this temperature as possible. Inside the case of amplifiers the temperature is maintained relatively low to ensure long life of components such as capacitors, which deteriorate with increased heat. Presently, no one in the audio field has directly addressed the thermal aspect of sound quality enhancement.
There is accordingly a need for an audio system that is capable of obtaining the transparent sound quality previously found only in vacuum tube systems, while maintaining reliability. The present invention satisfies this need, as well as others, and generally overcomes the deficiencies in the background art.
SUMMARY OF INVENTION
The invention is an audio sound quality enhancer which provides a transparent sound quality, using solid-state devices, which was previously available only in vacuum tube audio systems. In its most general terms, the invention comprises at least one solid-state component in the audio circuit signal path, and at least one heat source configured to heat the solid-state component or components. The invention increases the sound quality of solid-state audio systems by increasing the temperature of the semiconductor components involved in sound production. By intentionally heating the semiconductor components of an audio system above standard operating temperatures, the invention delivers sound quality levels normally only associated with vacuum tube sound systems. This invention provides a new class of solid-state semiconductor audio playing and recording compon
Cuneo Kammie
Dinh Tuan
Hayes & Soloway PC
Ridley Engineering, Inc.
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