Soundcard tips and facts
General facts to be aware
- Common problems and how to solve them
- General information about soundcards
- Recording from line level input
- Recording sound from microphone input
- Sound file formats
- Sound playback
- Tips on using microphones
General information about soundcards
Under the current model for PC audio, the majority of audio-related problem are the result of improper hardware configuration. Applications designed to run under the MS-DOSŪ operating system suffer the most, because users are sometimes required to inform the software of the current hardware configuration (I/O addressing, IRQs, and direct memory access (DMA)). Plug and Play has solved numerous resource conflicts for Windows-based applications, there are unfortunate side effects for MS-DOS-based programs. Specifically, the configuration of the audio hardware can change and get out of sync with what the MS-DOS-based application expects. Plug and Play card can be quite problematic to DOS application users.
Numbers on the sound card names can be misleading
No card is yet 32-bit, the number "32" and also the "64" are misleading. So misleading that many people talke about "32 bit soundcards" or 64 bit soundcards", but they are wrong.
32 means (in AWE32 and Terratec Maestro32) that 32 MIDI voices can be played at one point. The 64 means that 64 MIDI voices can be played at one point on the Terratec EWS64 (AWE64 can play 64 voices when it uses considerable amount of PC processor power to play half of those voices).
16 bits does not automatically mean CD quality
PC soundc cards and CD players are both 16 bit devices and can use same sample rate, but this does not meant the sound quality of those devices is the same. PC soundcards typically have much worse signal to noise ratio (around 80 dB) than CD players (>90 dB), which means that PC soundcards are more noisy. CD players have good straight frequency response from 20 Hz to 20 kHz, but PC soundcards typically have low and high frequencies attenuated noticably.
Signal to noise (S/N) ratio is one of the most important measurements (specs) to look for when purchasing any audio device. It measures the ratio of noise generated by the device, and added to the outgoing signal. Its measured in dBu and the higher the number the better.
Why the bass frequencies in many cheap soundcards are attenuated ?
A lot of cheap cards roll off the low end to increase dynamic headroom/reduce clipping problems on the little pc speakers which usually aren't equipped to handle low frequencies anyway. Sometimes unintentional bass attenuation is caused just because the analogue design has been made to be as cheap as possible and uses too small signal coupling capacitors.
What's problem with no-name cards ?
No-name cards have usually much more problems to get them to run and after they have it running once the problems aren't away. Now with name products you have support, web-page for new drivers and so on.
What is in typical soundcard ?
The picture blow shows the parts which are included in typical modern Wavetable soundcard (for example AWE32, AWE64 and similar):
Description of the parts:
- ROM includes the preset wavetable syntetizer samples
- RAM is for downloadable wavetable instruments
- Wavetable syntetizer makes sounds ouf of the samples in ROM and RAM
- CODEC does the A/D and D/A conversion of the audio signals
- FM syntetizer plays FM sounds (for orignal Sound Blaster/Adlib compatibility)
- MIXER is an analogue mixer IC which mixes together the sound from the various inputs to (microphone, aux input, wavetable syntetizer, FM syntetizer, CD-ROM audio,) to the final mix which is then sent to line level and speaker outputs.
Where I can find the block diagram of Sound Blaster 16 ?
The picture below has the block diagram of Sound Blaster 16:
This same block diagram applies also to vary many other simple PC soundcards.
Why only one Windows program can output sounds at the same time ?
The current Windows sound model has a significant shortcoming: You can only hear one application at a time. If you try to run the second sound application at the same time, the system will either omit sounds or present a dialog box indicating the audio hardware is busy.
What is the difference between full-duplex and enhanced full-duplex sound cards ?
Full Duplex = Sound card can record and play back sounds at the same time. Typically sample playback and recording sample rares must be same.
Enhanced Full Duplex = record at one sampling rate, play at a different sampling rate, simultaneously.
Can I connect my soundcard to home stereo system ?
Yes you can. Just plug the line level output of the soundcard to the stereo AUX or TAPE input. You need just a suitable cable and it will work nicely. With home stereos you can enjoy the much better sound quality than with your multimedia spakers.
Are there any problems associated when I connect the soundcard to stereo system ?
The connection itself should not cause any major problems. Depending on where the equipment are plugged and is there sny connections to antenna/cable Tv you might get a humming noise entering to your sound system. If you get this humming noise then it is caused by a ground loop problem. You can find lots of useful information how to find and solve ground loop problems at http://www.hut.fi/Misc/Electronics/docs/groundloop/.
Tips for installing card to PC
Your soundcard is very sensitive electronics so keep it away from noise soirces inside the PC. Install the sound card away from other noisy card in the PC bus (like modems, graphics cards, hard disk controllers). It is also a good idea to keep the soundcard away from the power supply and the wiring inside the PC.
Connecting sound card to your HIFI system
For best sound quality I would recommend you to toss out those cheap multimedia speakers because they sound really bad when you compare them to even cheap HIFI system.
Connect the sound card line level output to your stero system AUX or CD input. Do not use the speaker output of the soundcard because they sound bad. When connecting soundcard to HIFI system do it in the following order to avoid damaging any equipment:
- unplug the computer from mains
- turn off the HIFI system and turn the volume down
- connect the audio cable between soundcard and HIF system
- reconnect the PC to mains
- turn on the PC
- turn on the HIFI system
- adjust the volume in HIFI system
Common problems and how to solve them
Hissing sound in background
A typical problem: I just bought a new soundcard have noticed background hissing after a sound is played. It doesn't appear to be in the speaker system as I ran a portable cd into it.
PC soundcards are cheap consumer electronics and they are built using cheap parts using designs which are not the best possible. This causes that soundcards electronics generate noise and pick up interference from other electronics inside the PC. You hear all this as hising noise in the soundcard output.
The soundcard design has effect how little noise you can get, but usually the reason for most noise is not the soundcard, but how you use it. You can even make the best studio audio system hiss very noticably if you set the settings to very non-ideal values. Soundcards are typically used by people who do not know how to use audio systems properly which causes that they set up the systewm baddly which leads to very poor performance.
Some tips for users of Sound Blaster family of soundcards:
- The obvious would be a microphone enabled. Mute it. (Win 95 mixer)
- Next would be gain settings set at x4, change it to x1 (CL Mixer)
- Turn 3D Stereo Enhancement off. (Device Manager)
If you you soundcard connected to amplified multimedia speakers or hifi system remember to use line level output connector. Line level output connector typically gives out better sound quality and less noise.
Humming noise when I connect my soundcard to my hifi system
You have quite propably ground loop problem or bad audio wiring in your system. Check the wiring. If the wiring does not have any fault, then check the ground loop problem. First remove the antenna wire going to you receiver going to your hifi system. If your humming goes away, them you have a ground loop problem caused by antenna wire. This kinds of problems can be most easily solved using antenna cable isolator. For more information about ground loops go to my AV systen ground loop web page.
Recommended soundcard output settings
Set the soundcard output level to the center position is a general advice. If you use too low output level in the soundcard you have to turn on the amplification in your multimedia speakers or HIFI system higher and you get more noise. Do not turn the output level slides to maximum position, because soundcards typically distort quite noticably if you play back some loud sound through them if the gain setting are in maximum position.
All computer soundcards emit a certain amount of noise. Make sure your amplifier/powered speakers are plugged into the soundcard's line-out (not speaker-out, powered-out or headphone-out), and make sure the treble is set to flat in your soundcard's mixer. If you're not wearing headphones, at reasonable listening volumes, the noise should be fainter than the computer's fan. If you are getting excessive noise the noise source might be a noisy card instelled near your soundcard or a poorly shielded CD-ROM drive audio cable.
You could also try muting functions on your sound card your not using, The microphone input amplifier usually kicks out a lot of noise. If you have not already done so try to situate your sound card as far away from the PSU and CPU as possible. Every Creative Labs sound card I've experienced doesn't really have a high SNR so you can expect some noise in the sound.
Distortion problems on playback
Any sound device distorts when you feed to strong signals to it. Soundcards nowadays typically have many sound generating parts on them (D/A converter for sample playback, syntetizer, etc.) and the sound from all those sources are mixed on the mixer chip.
Mixer chip has gain settings for all of it's inputs and output volume. If you turn up the input gains of the mixer chip too high the mixer can't handle strong signals form that input properly and this causes distortion inside the mixer. If you turn the output volume too high you get the output amplifer easily cause distortion.
For some strange reson some SB32 rivers from Creative Labs set the gains of input and output amplifiers for x2 position, which causes quite often noise and distortion. Those gain settings can be set using the tools coming with card to x1 and this should stop the distortion. Remeber always to use line level outputs instead of the spaker output when you connect your soundcard to external amplifier (the spaker amplifer adds noise and distortion to the sound).
There is also distortion problems where people usually blaim the soundcard but those are cause by some other reasons. This distortion which is not caused by the soundcard different than the normal overload distortion because it is actually short breaks in the sound (so short that you can't noce them as breaks). This kind of problem is caused in the situation where the operating system is not able to output new sound data to soundcard when it needs. For example Windows 95 operating system may have difficulty with real time applications for many reasons. This problem is typically cause by system overload (too many applications running) or some other pripheral is taking too much time and prevents the soundcard to take processor or bus time when it needs. Thypical reaosn for this kind of problems is the graphics card. Some computers require that software wait for the hardware to be ready to receive new data. Many display drivers (are NOT normally set to do this because it slows them down slightly and it's not necessary for most computers. For example Matrox tells how to change settings in Win95 to correct the distorted sound problem with their graphics cards on the support documents at their web site at http://www.matrix.com/. If you have some other graphics card check their web site if you can find there tips how to solve this problem.
If you get beaks in the sound playback then it is a good idea to check Windoes virtual memory settings. Normally Windows 95 changes the virtual memory setting automatically on run-time. When Windows 95 increases the size of the swap file this operation takes almost all processor time at high priority. By changing the swap file size to become permanent (upper and lower limit are same) you stop Windows from wasting processing power to swap file handling.
My sound is messed up. On some of my CD's I can hear the music but not the voices. What is the problem ?
This kind of problem is quite often cause by the wrong wiring in the speakers. Swap the wires on one speaker and try again.
Recording from line level input
Match the signal output and card signal input level
If you set recording level too high you get distortion to your sound and you can't get that distortion out from the digitized sound in ay way. If you set the level too low you get lots of noise to your sound. You can't get rid of that noise in you sound in any way.
Record at best sample rate
To prevent aliasing in the sound it is best to make all recordings you wan to do at the maximum sample rate (typically 44.1 kHz). If you need lower sample rate samples, then use GOOD QUALITY conversion tools to convert the sample rate to lower values. Good conversion software does the filtering which removes the high frequency components from the sound and prevents the aliasing.
Record always at 16 bit resolution
Always use 16 bit resolution in recording because this gives the best results and most headroom. If you need 8 bit samples, record at 16 bit, adjust the sample level to bets value using sample editor and then save as 8 bit sample.
Prevent ground loops in your wiring
Ground loops easily pick up humming and other noise to your system.
Recording sound from microphone input
No sound when I try to record from microphone
First check that you have the microphone input selected as the recording source and the gain of it turned up enought to give acceptable signal levels. Typically the soundcard mixer control software allow you to control the recording source, sound input gains and muting.
I own a fairly recent SB16 PnP, and it has two different mutes in the mixer program:
- The GREEN button would allow playback (over the speakers)
- The RED button would allow recording (to a wav file)
If you have the soundcard settings done right ant you can't still get sound fro microphone then you have to check that you have a working microphone and the microphone is suitable type for your soundcard. There are two types of microphones in the market: dynamic microphones and electret microphones. Check which microphone type your sound card needs and use correct microphone type, otherwise you will not get any sound or the volume will be very low.
I can't get any sound recorded from mic input
Does anyone know why the microphone would work yesterday, and not today? There have been no changes to the system at all. The microphone works on other machine, so it isn't the problem??????
Sometimes, the volume mixer doesn't always save its settings. So, you should check to see if the microphone is selected as a recording device and also if the volume is properly set. Check also that the micropone is correct type to for your soundcard. If the microphone has on/off switch make sure that is on.
If you are using Windows95 it might be a good idea to also check other multimedia settings. By uncheckin the "Use preferred devices only" box in the multimedia control panel can solve the problem sometimes.
I get very low volume when I record using microphone
First check that you have enough gain set in the input setting. If you have the gain set to maximum value and you don't get enough volume the microphone might not be suitable for ypu soundcard. Sound Blasters want electret microphones which give enough high signal levels. Of you connect cheap dynamic microphone to them you don't get enough high signal level for soundcard.
For more information about connecting different microphones to soundcards take a look at Interfacing Microphones to Computer Sound Cards application note from Shure web site.
I get very much hissing from microphone
The problem is not usually in the microphone. Normal dynamic microphone does not cause any more noticable hissing than the therminal noise inside microphone coil wire resistance (this noise is neglectable in normal consumer audio systems). So dynamic microphone do not cause that hissing, although it might be pick up magnetic interference (like high frequency noise from monitor or humming from nearby transformer. The source for hissing is the microphone preamplifier, not the microphone itself. The hissing is from the cheap microphone preamplifier inside your soundcard. If your microphone is a cheap multimedia microphone (for exampl Sound Blaster microphone) the hissing can be also from the preamplifier inside the microphone (small electret microphones indeed have a built-in small preamplifier inside them).
To solve the problem try to turn down the gain in the micrphone input using the mixer program which comes with the soundcard. If the microphone input has automatic gain control try to set that off, because AGC turns the gain up when there is no signal coming from the microphone.
Generally the microphone premaplifers in computer soundcards are very noisy and the hissing is quite unvoidable. If you want good samples withou hissing consider getting good soundcard, good microphone, external microphone preamplifer and make sure that there is not noise sources (like your PC) in the same room where you try to record. If you are serious about your audio work it might be worthwhile to invest to an audio mixer which has a built-in microphone preamplifier and connect it to the line input of the sound card. Most people who use sound cards ultimately end up using a mixer for something or other, so this might be a good excuse to get one.
Tips on using microphones
Turn off the speakers when you record
If you keep the speakers on when you record you get bad sounding echo from the speakers to your sound. At worst case you get acoustick feedback which causes whining noise.
Turn off noise sources
Every noise in the room gets to the sampled sound when you record and you can't get rid of them afterwards. It is best to make sure that the room is quiet enough that you don't get too much extra noice.
Avoid room echo
Try to have your room acoustics so that you get as liitle as possible room echo to the sound. Echo can be easily added to the sound but it can't be removed from it. And if you try to add echo to sound which already has some echo it will sound bad.
Use good microphone
There are many different kind of microphones in the market. Get the one which gives good sound quality and the characteristics are what you need. Omnidirectional microphones record sound coming from all rections. Cardoir microphones pick the sound coming from front and attenuate sounds coming from other directions quite much. With cardoid microphone you pick less envirnmental noise when you talk to it, but you know how to talk to it.
Cheap multimedia microphones are usually omnirections and will generally sound bad. The problem is that you can't get good resuluults with some soundcard when you connect professional microphone to them (for example Sound Blaster family of soundcards form Pro to 32 have too low -20dBV (100mV or 0.1Volt) to be usable with any professional dynamic microphone).
Use external microphone amplifier
The microphone amplifiers in soundcards are generally bad. They are noisy, pick up interference form computer, add distortion and have typically bad frequency response. If you plan to do something serious consider getting an external microphone amplifer which you connect to your soundcard line input.
Sound file formats
What are WAV files ?
WAV files are the file format which windows uses for storing digitized sounds.
What is MIDI format ?
MIDI is a digital interface used to interface music syntetizers and computers together. MIDI interface transfer note on/off command and other syntetizercontrolling information. The syntetizer then plays out the notes which come from the MIDI interface in the way descibed in the MIDI interface commands. MIDI file format is a file format to store all this information to a data file in computer. If MIDI file is played though a syntetizer or computer sound card you will hear the same notes as in the song but played back using the sounds your syntetizer or sound card has. The music quality then depends on how good sounds your sound playback device has and how similar they are to those which the maker of the song had.
General MIDI is a stadardized set of midi insruments to guarantee that all general MIDI sound cards have same set of instuments available and use the same instrument numbers. General MIDI does not guarantee that those insturuments will sound anywhere near the same in different sound cards or syntetizer (it just guarantees that for example if song asks for PIANO it will get some piano sound).
What is MP3 format ?
MP3 file format is a way to store sounds and music using MPEG Audio Layer 3 compression. MP3 format is usually used to store music in computer environment because it provides about 1:10 compression and it is many times quite hard to tell the difference between original CD and the MP3 compressed audio (unless you have a very good audio system and good listening experience). MP3 format is quite useful because you can easily fit a near CD quality song to 3-5 megabyte file and those files can be played back through your sound card in real-time using suitable software (many programes need at least Pentium processor to work in real-time). Compressing digitized audio to MP3 is possible with suitable software, but that compression takes quite long time because there is lots of processing needed in this compression.
Using compression in sound files
Compression of audio files allows you to fit the sound files to smaller space and still sound almost the same. There are lots of different sound compression methods in use. The general rule is that every time you compress a sound it gets worse. So if you plan to process your sound files afterward, do not use compression in you workign files. When you have made you sound ready, then make a compressed version of ready sound for distribution.
Tomi Engdahl <[email protected]>