Abstract:
A computer system includes a motherboard, a signal amplifier circuit integrated onto the motherboard, and a processor for controlling operations of the computer system. The signal amplifier circuit includes a Class-A preamplifier, a filament heating circuit, and a voltage booster and regulator circuit. The Class-A preamplifier has a vacuum tube so that the computer system can produce professional sound output.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a computer system, and more particularly, to a computer system with a motherboard having a vacuum tube preamplifier circuit.  
           [0003]    2. Description of the Prior Art  
           [0004]    Personal computers have become a necessity in our modern life. What a personal computer can be used for is simply up to a user&#39;s imagination. Currently, IT vendors are working hard to port everything electric appliances can do to personal computers.  
           [0005]    For example, during the period that the IBM® XT computer prevailed, game programmers could only utilize a simple circuit for generating single frequency music through a poor PC speaker. The other option for more enthusiastic players was to buy an optional sound card for better quality of sound. However, these kinds of sound cards could only generate MIDI music stored on a ROM chip, and only certain types of sound cards could deal with low quality wave sound. Additionally, most IBM-XT PCs were equipped with a monochrome CRT monitor, and thus could not display any colors other than white or green. Moreover, IBM-XT utilized a 16-bit Intel® 8088 microprocessor, running at 4.77 MHz, and yielded performance of less than 1 MIPS, which is far behind the minimum requirement for decoding MPEG video/audio (in general, 60 MIPS is required). Besides, most IBM-XT PCs had only two low-density, double-sided floppy disks, rarely any of them having a hard disk. Low volume disk storage meant the capacity of the software was limited, and for games, it is not hard to imagine that the games would be limited to text. On the contrary, game consoles during that period like Nintendo® or Sega® preformed much better in video, audio, and in overall entertainment. Therefore, in those days PCs could neither replace any electrical appliances nor any game consoles. PCs seemed to be nothing affiliated with our daily lives and were basically an advanced typing machine.  
           [0006]    Now, computer technology has advanced rapidly in every extent. Performance of microprocessors, which was formerly measured in units of KIPS (kilo-instructions per second), is now measured in GIPS (giga-instructions per second). In mass storage, a 100 GB hard disk is becoming a basic standard accessory to a PC. This means a PC has more capacity for storing plenty of multimedia files so that games can be more realistic. Video card vendors do not emphasize the ability for displaying 2D windows-based environments any longer. Current video cards are mainly designed for displaying splendid and magnificent 3D scenes. And now, most sound cards are capable of outputting high-quality wave-files in real-time and simulating surrounding and environmental sound effects using powerful digital signal-processing chips.  
           [0007]    All these technologies have improved a PC&#39;s multimedia ability significantly. To sum up, a PC with a mainstream 3D video card and a recent microprocessor, when connected to the Internet, allows a user to play 3D games with players from all around the world. With all these features, the PC&#39;s capability for playing games has almost bypassed that of game consoles. A PC with a TV-card allows users to watch TV programs and listen to FM radio broadcasts, and accordingly the users no longer need to buy a TV set or a radio. With an additional MPEG encoding card and a CD-RW, a user is able to record TV programs onto a CD for future viewing. With a CCD, a PC can act as video camera. With a DVD-ROM, a LCD-projector, a high-end sound card, and a corresponding speaker system, PC can make a home into a movie theater. With advances in design and the process of VLSI, these technologies have improved substantially. For example, there were formerly 13 IC chips required for DVD decoding, but because of the development of SOC technology, these 13 ICs have been integrated into one single chip.  
           [0008]    The improvements of the last 20 years allows for tiny but extremely fast processing products, however, there are still things that VLSI cannot replace. One of these things is a speaker. There are two main types of speakers, vacuum tube amplifier and solid-state amplifier. Vacuum tube amplifier speaker systems have survived until now even though vacuum tube digital circuits have been extinct for a long time. This is due to a remarkable characteristic of vacuum tube amplifier speaker systems that is to cause amplified sound to be acoustically harmonic, clear, precise, and powerful. This is unreachable using a solid-state amplifier. Thus, audio professionals always prefer vacuum tube amplifier systems.  
           [0009]    Current PCs are brilliant in audio and video functionality. When it comes to video, large-scale LCD projectors and plasma displays are available. However when it comes to audio, though high-end positional audio systems have been fulfilled in chip form, there is still a lack of corresponding high-end speaker systems.  
         SUMMARY OF INVENTION  
         [0010]    It is therefore a primary objective of the claimed invention to provide a motherboard having a vacuum tube preamplifier. Since devices on motherboard are complex, unlike a typical external vacuum tube amplifier, problems of signal interference and limited space are addressed by the claimed invention. Hence, the claimed invention must compress a vacuum tube preamplifier into a limited region on the motherboard in an environment having pluralities of clock signals and ICs.  
           [0011]    According to the claimed invention, a computer system comprises a motherboard, a processor for controlling the computer system, and a signal amplifier circuit integrated on the motherboard. The signal amplifier circuit comprises an amplifier for amplifying an audio signal, wherein the amplifier comprises a vacuum tube for current amplifying the audio signal.  
           [0012]    After installing the motherboard having the vacuum tube preamplifiers, the computer system according to the claimed invention is able to output acoustically harmonic, clear, precise, and powerful audio. This makes a PC equipped with the motherboard of the claimed invention not only a plain PC but also a professional preamplifier.  
           [0013]    These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0014]    [0014]FIG. 1 is a schematic diagram of a computer system according to the present invention.  
         [0015]    [0015]FIG. 2 is a schematic diagram of a class-A amplifier of the signal amplifier circuit of FIG. 1.  
         [0016]    [0016]FIG. 3 is a schematic diagram of a voltage booster circuit of the signal amplifier circuit of FIG. 1.  
         [0017]    [0017]FIG. 4 is a schematic diagram of a filament heating circuit of the signal amplifier circuit of FIG. 1. 
     
    
     DETAILED DESCRIPTION  
       [0018]    Please refer to FIG. 1. FIG. 1 is a schematic diagram of a computer system  8  according to the present invention. The computer system  8  comprises a processor  9 , a motherboard  10 , a signal amplifier circuit  11 , an integrated sound chip  13 , a first switch  15 , a sound card  17  installed in a PCI expansion slot, and a frequency isolation wall  12 . The integrated sound chip  13  is electrically connected to the signal amplifier circuit  11 , wherein the first switch  15  determines the connection. The motherboard  10  automatically detects the setting of the first switch  15  to determine if the signal outputted from the integrated sound chip  13  goes through the signal amplifier circuit  11 . Additionally, signals generated from the integrated sound chip  13  are directly outputted from a lineout port  21 . The signal amplifier circuit  11  further comprises a riser card slot  30  and a corresponding riser card  19 . The riser card  19  comprises a line-in port  23  and a lineout port  25 . The line-in port  23  allows the sound card  17  in the PCI slot of the motherboard  10 , a DVD-player  32 , or any other external device to take advantage of the signal amplifier circuit  11  by plugging a signal cable into the line-in port  23 . The lineout port  25  is for outputting the signal amplified by the signal amplifier circuit  11  to a next stage amplifier.  
         [0019]    Please refer to the frequency isolation wall (FIW)  12  shown in FIG. 1. The FIW  12  is a signal isolation device for isolating the precision-demanding signal of the signal amplifier circuit  11  from complex clock signals and other digital signals of the motherboard  10 . The FIW  12  substantially limits interference between circuits, devices, and ICs of the motherboard  10  and the signal amplifier  11 .  
         [0020]    Please refer to the signal amplifier circuit  11  shown in FIG. 1. When the computer system  8  starts up, a power supply  6  supplies the signal amplifier circuit  11  with 12V DC power. The signal amplifier circuit  11  comprises the following parts: a class-A current amplifier  14 , a voltage booster circuit  16 , a filament heating circuit  18 , the riser slot  30 , the riser card  19 , and a second switch  20 .  
         [0021]    Please refer to FIG. 2, which is a schematic diagram of the class-A current amplifier  14  of the signal amplifier circuit  11  of the present invention. The class-A current amplifier  14  comprises a double triode  40 , a vacuum tube holder  42 , a left side input end  22 , a right side input end  24 , a left side output end  26 , a right side output end  28 , two input end filter circuits  44 , and two output end filter circuit  46 . The double triode  40  is made in a nine-pin style, which comprises two plate electrodes  52 , two grid electrodes  50 , two cathode electrodes  54 , and a filament electrode  58 . The signal inputted into the left side input end  22  and the right side input end  24  is then sent into the two input end filter circuits  44 , and finally, the signal is inputted into the grid electrodes  50  of the double triode  40 . After the signal is amplified by the vacuum tube, it is then inputted into the two output end filter circuits  44  and at last the signal is outputted from the left and right output ends  26 ,  28 . The class-A current amplifier  14  has no effect of voltage amplification, and its other characteristics include large inputting impedance, low outputting impedance, with the input signal and the output signal being in phase. The signal amplifier circuit  11  can further comprise a voltage amplifier cascading with the class-A current amplifier  14  to obtain advantages of both a voltage amplifier and a current amplifier. A heating voltage of the filament electrode  58  of the double triode  40  is 6.3V and is supplied by the filament heating circuit  18 . An operating voltage of the plate electrode  52  of the double triode  40  is 115V, which is supplied by the voltage booster circuit  16 .  
         [0022]    Capacitors of the two input end filter circuits  44  and  46  and grounded resistors connected to the cathode  54  of the double triode  40  can be adjusted according to user preferences. Adjusting the capacitors of the input end filter circuits  44  and  46  allows for changing frequency response of the filter circuits  44  and  46 . Adjusting the grounded resistors connected to the cathode  54  allows for changing operating voltage of the whole class-A current amplifier  14 . In addition, the double triode  40  of the class-A current amplifier  14  is plugged into the vacuum tube holder  42 , which means that the vacuum tube is replaceable and changeable.  
         [0023]    Please refer to FIG. 3, which is a schematic diagram of the voltage booster circuit  16  of the signal amplifier circuit  11  shown in FIG. 1. The voltage booster circuit  16  comprises a regulator  60 , a transformer  62 , a MOSFET  64 , a Zener diode  66 , and a low pass notch filter  68 . 12V DC power is inputted into the transformer  62  from a power supply  67 . Meanwhile, the regulator  60  outputs a high frequency clock to turn the MOSFET  64  on and off. Therefore, the supplied 12V DC power is converted to AC power that the transformer  62  can work with. After the AC power is stepped up, it is then inputted into the Zener diode  66  and the low pass filter  68  to be half-wave rectified by eliminating the AC portion of the power. The power is then sent into the plate electrode  52  of the double triode  40  of FIG. 2. The voltage output at the output end  70  of the voltage booster  16  then goes through a voltage divider  72 , which divides the power and feedbacks to the regulator  60  for stability. In the preferred embodiment, the output voltage is 115V, and the second switch  20  is responsible for turning the regulator  60  on or off. One end of the second switch  20  is electrically connected to a south bridge chipset  74  on the motherboard  10 . When the outputted signal from the south bridge chipset  74  goes high, the second switch  20  is turned off, and the entire signal amplifier circuit  11  is also turned off. On the other hand, if the outputted signal from the south bridge chipset  74  goes low, the second switch  20  is turned on and the entire signal amplifier circuit  11  is able to turn on.  
         [0024]    Please refer to FIG. 4, which is a schematic diagram of the filament heating circuit  18  of the signal amplifier circuit  11 . The main purpose of the filament heating circuit  18  is to generate 6.3V DC power from the 12V DC power supplied by the motherboard  10 , and then to heat the filament electrode  58  of the double triode  40  to an operating temperature in a short time.  
         [0025]    Since DC power is supplied by the power supply  6  of the computer system  8 , the signal amplifier circuit  11  does not need to include another power supply circuit, thus reducing space required. In addition, the signal amplifier circuit  11  has been designed to take full advantage of VLSI technologies in that fewer ICs and discrete devices appear on the motherboard  10 . This makes the signal amplifier circuit  11  of the present invention perform substantially the same as a typical external vacuum tube amplifier, while consuming much less space.  
         [0026]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.