How Sound Cards Work In Personal Computers

A sound card uses typically one of three methods to produce sound in a personal computer. They are all briefly outline below.

FM Synthesizer

The synthesizer is the actual mechanism that delivers the sound through your speakers. The cheapest sound cards employ the FM synthesizer technology to generate sounds simulating various instruments, similar to a keyboard synthesizer.

Wave Tables

The wave table technology used by sound cards is the most expensive type of sound technology.  With wave table sound, sounds on the sound card are recorded from real musical instruments.  For example, you can record from a real piano and make a small sampling on the recording.  This sample is then stored on the sound card and when you invoke the music to play, you are actually listening to the samples generated by the sound card.  With a high end sound card (at the time of this writing was a SoundBlaster Live 5.1), very impressive sounds can be produced. Bottom line is like any PC hardware, the more money you spend, the better quality component you will receive.

Physical Modeling Synthesis

This type of synthesis arrived as a third sound producing technology.   Physical modeling synthesis has proven to be quite complex in that  programming is involved to produce and simulate sounds through the sound card.  It does, however, have some very promising advantages. The relatively inexpensive Sound Blaster Gold  sound card contains approximately 14 instrumental sounds each of which are created from the physical modeling synthesis.
Sound Card Jacks

Jacks are one-hole connecting interfaces on your audio card. They allow you to attach other devices to your card. Jacks are found exclusively on the rear panel of audio cards as shown in the following illustration:

Typical connectors found on a Creative Labs Sound Blaster AWE64 ISA Sound Card.

Overview of Sound Card Interfaces

Sound cards can use either a Peripheral Component Interconnect (PCI) Interface or Industry Standard Architecture (ISA) based interface.

PCI is a far more advanced bus type for connecting expansion cards and offers a higher data transmission rate.

Older ISA cards were very limited in the maximum speed they could transfer data to and from other devices in a system. As a result of this limitation ISA cards can be considered obsolete.

Sound Card Interface Comparison

The points listed below best summarizes the pros and cons between the PCI and ISA interfaces so that you can compare how the technology has evolved over the past decade.

PCI

PROs

• The higher allocated bandwidth format allows for better audio effects.
• Utilizes less resources.
• Allows 90 db noise ratio.
• Easier installation.

CONs

• Higher cost.

ISA

PROs

Relatively low cost.
Proven to be reliable.
Compatible with the Sound Blaster standard.

CONs

• Data transfer is slow.
  
• Uses valuable IRQ and DMA settings.
• Limited noise ratio of 85db.
• Non plug and play technology makes installation difficult.
• Hardware is becoming or has become obsolete.

Sound Card Standardization Through Creative

Creative Labs has dominated the sound card industry for many years.  It had set the standard in digital sound with the introduction of their family of sound cards.  The older 8 bit sound card was quickly followed by the 16 bit card offering better sound quality through the larger expansion bus. Although mediocre by todays standards, the 16 bit sound card was designed as an entry level sound card best suited for home users.

The SoundBlaster 16

The SoundBlaster 16 was capable of playing sound with a high level of quality while maintaining the SoundBlaster compatibility introduced by Creative Labs.  Available in the ISA format only, the standard 16-bit Creative Labs Sound Blaster card is compatible with all major applications, and operating systems.  The Sound Blaster 16 is typically available in the ISA format.

The SoundBlaster 64 AWE

Creative Labs introduced the Sound Blaster AWE 64 designed for the home user, gamer, or multimedia specialist.  The AWE64 card provides advanced sound functions but still provides the basic SoundBlaster compatibility to ensure all software and applications are compatible with the AWE64.  A new level of reality is added to all games and applications with the AWE64 card.

The SoundBlaster 128

The PCI128 also introduced by Creative Labs provided an even higher level of performance to any type of game or application. The PCI is the card of choice for many gaming enthusiasts as it provides true stereo sound while still retaining the Sound Blaster compatibility. Because it employs the PCI technology there is no compatibility issues to be aware of.  The Sound Blaster will work with any operating system including MS-DOS and Windows.  The PCI128 has two stereo output jacks, which allows you to use 4 indpendent speakers allowing you to enjoy real stereo sound.  The PCI128 is only available using a PCI bus interface.

Introduction To DMA

Expansion cards have to request the CPU to send the same information over and over again. To avoid this repetition and resulting bottlenecks in a system the processor communicates with a card through Direct Memory Access (DMA) channels. DMA is a technology that defines how data travels through different parts of the PC.

Base memory addresses are often referred to as Input/Output (I/O) ports. CPU’s respond to an Interrupt Request (IRQ) and as a result, a different route can be configured and communicated through the system, thus enabling the processor to complete its tasks faster.

There are a varying number of I/O ports available to communiate with a PC. These ports can also be refferred to as "memory addresses" and typically take the format 02E8 or 03E8. These addresses are specific parts in memory in which the processor and sound card communicate with each other to get things done.

DMA (Direct Memory Access) Channels

DMA channels permit a direct pathway for hardware devices to communicate with other peripherals in a computer without any CPU intervention. Systems utilizing DMA can transfer data at a much faster speed than non-DMA based systems. Older mainboards and hardware devices required the use of a seperate card and device drivers to take full advantage of DMA benefits. Newer parts and operating systems (such as Windows XP Media Centre Edition) have built in support for DMA, thus requiring no additional hardware or software support.

Sound cards, floppy drives, and some older style hard drives employ DMA protocols. The following table illustrates the most common types of devices that take advantage of DMA protocols.

IRQ’s (Interrupt Request Level)

IRQ's are basically “stop and do this” messages given to the CPU when a device calls on the CPU to complete a task. For example, each time you press the Enter key on the keyboard, the keyboard controller sends an IRQ instruction to the CPU demanding it to carry out that function.

Each component in a computer must be configured to use its own communicaton line or IRQ setting for the successful transmission of data.

Some hardware devices share interrupt requests peacefully within a Windows system. If two devices are configured to use the same interrupt request conflicts will occur often resulting in neither of the hardware devices working.

The following table summarizes the most popular IRQ settings and the devices they are in charge of.

IRQ # and  Typical Device(s) Controlled:

• 0     System Timer
• 1     Keyboard
• 2     Some video cards
• 3     COM2, COM4
• 4     COM1, COM3
• 5     Sound Card
• 6     Floppy Drive Controller
• 7     LPT1 (Printer Port)
• 8     CMOS Clock
• 9     Redirected to COM2, Power Management / ACPI Controller Function.
• 10     Serial Bus Controller
• 11     Display Controller
• 12     Network Controller
• 13     Math Coprocessor
• 14     Hard drive controller
• 15     Free
• 16     USB Host Controller
• 18     Hard Disk IDE Controller or USB Host Controller
• 21     Wireless Network Controller
• 22     Multimedia Controller, Television Tuner Card, or Video Capture Device
• 23     Audio Controller or USB Enhanced Host Controller

Many operating systems have utilities that allow you to check the IRQ settings for your computer. If you are running DOS, MSD (Microsoft Diagnostics) is the program you need to use to view information about the configuration of your computer. In Windows XP the System Information tool can provide you with extensive information about the hardware in your computer.

Summary Of Internal Connectors On A Sound Card

The list below summarizes various connectors normally found on a sound card.

INTERNAL CONNECTORS

• CD Audio Connector - Facilitates the playback of audio CD's and DVD's.
• Telephone Answering Device Connector - Facilitates audio connections between voice modems and microphones.
• Aux Connector - Facilitates audio connections between the sound card and internal video capture devices including television tuners and MPEG capture cards.
• CD SPDIF Connector - Facilitates the audio connection between the sound card and a CD-ROM or DVD-ROM's digital audio output connector.

EXTERNAL CONNECTORS

• Analog / Digital Out Jack - Facilitates the audio connection between the sound card and a digital speaker system or compressed AC-3 output system also known as SPDIF.
• Line In Jack - Facilitates the audio connection between the sound card and an external device such as VHS and cassette recorders.
• Microphone In Jack - Facilitates the audio connection between the sound card and an microphone for direct voice recordings.
• Line Out Jack - Facilitates the audio connection between the sound card and a set of externally powered speakers or headphones.
• Rear Out Jack - Facilitates the audio connection between the sound card and a set of externally powered speakers or headphones.
• Joystick / Midi Connector - Facilitates a data connection between the sound card and a gamepad, joystick, or MIDI (Musical Instrument Digital Interface) device.

Sound Card Installation Guide

The installation of a sound card is one of the simplest installations you'll perform in a PC. The tough part will more than likely be in resolving DMA issues. But even by today's operating system standards, the likelihood of a problem arising due to a DMA or other configuration is highly unlikely due to a sound card's universally accepted formats for processing audio information.

This section will provide you with an understanding of how to install a Sound Blaster compatible sound card.  This installation walks you through the entire process of installing, configuring, and playing around with a Sound Blaster Live PCI based sound card.

Tools Required For The Installation

The following items are required for the installation of an internal sound card.

1. The sound card.
2. Any manuals that accompanied the sound card.
3. A standard Phillips screwdriver.
4. One star-head screw.
5. CD Audio cable.
6. Modem TAD (Telephone Answering Device) Cable (optional).
7. Auxillary Audio Cable for establishing a supplementary connection from the sound card to another multimedia based internal device (optional).

Installation Instructions

   1. Turn off the computer and unplug the black electrical cable that connects to the PC's PSU (Power Supply Unit).

   2. Find an empty PCI based expansion slot in your computer. These expansion slots are white in color.

   3. If there is a metal bracket covering the free PCI slot you've located, use the Phillips screwdriver to remove the screw, and place it in a safe location such as a toolbox compartment.

   4. Check your sound card manual for any jumpers that have to be set or changed. Newer type of sound cards employ true plug and play technology so jumper settings and dip switches are of no significance, but double check the user manual to be sure.

   5. The next step is to insert the sound card into the free PCI slot you located in step 2.

   6. Grab ahold of the sound card using two hands and line up the card, so it will fit in perfectly align with the chassis. Inserting PCI cards typically do not require a whole lot of force to fit properly so take some time and insert the card gently, ensuring the card lines up properly with the metal hole on the chassis.

   7. Secure the sound card to the metal chassis using the screw you removed in step 3. The card will get extra support when the screw is tightened to the chassis.

   8. Now that the sound card has been installed, you can continue to attach a variety of different audio cables to get extra value out of your hardware. The following table summarizes the most common audio sources that can be used when making cable connections through a sound card.