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Achieving The Best Recording With A Soundcard
Although Mac and PC soundcards have improved greatly over the years, this doesn't automatically guarantee better recordings. Sometimes it can be difficult to get your input signals to actually appear in the on-screen level meter, and even when they do, people still complain of unwanted distortion, high background noise, or break through of unwanted signals from elsewhere. If you're relying on your computer to monitor the input signals, rather than using an external hardware mixer, you've also got to set up some sort of internal monitoring, and if set up incorrectly this can cause digital feedback.
Here are answers to some of the most common questions about recording quality with soundcards.
1. Why do I get so much background noise on my soundcard recordings?
This is the most common question of all, and there are various possible reasons why the quality of soundcardrecordings can be marred by noise. Background noise is normally a sign that the input signal has beenrecorded at too low a level, which should be fairly easy to correct, but can also be due to other things. Forinstance, if your soundcard features a mic input, and your line-level recordings have a lot of background noise,check that the mic input fader is turned right down, and preferably muted altogether if possible.
If you really want to squeeze the quietest recording from a soundcard, and its mixer utility provides some form of input gain or level control, do a few checks at different settings to see whether the amount of background noise changes when you record 'silence' (with no input plugged in). If it does, and you have a hardware mixer, it may be better to leave the soundcard input level near its optimum setting, and adjust levels using your external mixer. Many soundcards provide up to 20dB additional gain beyond their nominal 0dB input setting, but you will get better recordings using the soundcard at settings around 0dB and using higher-level input signals.
If you are recording using a mic, bear in mind that the mic preamps on soundcards aren't likely to compare with those on even budget hardware mixers or stand-alone mic preamps. This is because thecomputer is a noisy electrical environment, and providing the necessary high levels of amplification on asoundcard can introduce all sorts of stray hum, buzzes, and hisses.
2. Why can't I hear anything when recording or playing back audio?
This is the second most common question, and locating the source of the problem can be an extremelyfrustrating experience. If soundcard signals are missing, it is generally because one of the software mixercontrols is accidentally turned right down. Confusion is often arises because there are several controls availablewith similar functions; if you get used to setting levels inside a MIDI + Audio sequencer application, you mayforget that there is an additional mixer utility elsewhere. Windows provides a general Volume Control utility thatcan be launched from the Taskbar; if you don't have this installed it can be made to appear by ticking theappropriate box of the Audio page found under Control Panel/Multimedia. Playback and Recording controls areshown in two different pages, and you can choose which is displayed by selecting Properties in its Optionsmenu. Often the cure for a missing signal is simply to launch the Volume Control utility and turn the offendingsignal level back up.
If your soundcard has a dedicated DSP mixer utility available there will probably be many more options forrouting, monitoring, and effects, and therefore more possibilities for missing signals. If your playbackdisappears, or your input signals can't be heard when recording, the prime candidate is a mis-routedmonitoring system. Many soundcards now provide 'zero'-latency input monitoring for recording purposes, but insome cases you will have to switch this off again manually after recording before you can hear your tracks playback normally. Do take the time to study the possibilities in the manual, since there may be several ways to setup monitoring for recording purposes. Sadly, some software is not exactly what you'd call intuitive, and the bestway to understand the possibilities is to spend an hour or so recording and playing back signals while trying outthe different options -- which leads us neatly to the next question.
3.Why do my recordings always have a little bit of previous tracks recorded along with the newinput signal?
I've had various emails from readers complaining of 'ghostly' versions of previous tracks being added to fresh recordings This is nearly always due to incorrect setting up of the sound card's monitoring facilities: for instance the SB Live! card has a 'What U Hear' function that allows you to record the entire output of its software mixer. If this is selected when multitrack recording, existing tracks will get mixed in with fresh ones,which is not normally what you want. Most musicians will want to monitor their performance at the same time ashearing existing tracks being played back, to enable them to keep in time, but will want to record the performance in isolation.
To check that your mixer (either an external hardware one or a software one) is correctly routed, temporarily unplug your input signal, and try a dummy recording. If the input meters still move during the recording, and the track contains anything but a little background noise, then something's amiss, and you need to track down where the stray signal is coming from. You may have to resort to reading the manual again to find the manufacturer's suggested routing, but in most cases it should be possible to monitor inputs and outputs simultaneously without needing an external hardware mixer.
Another potential problem with incorrectly routed mixer utilities is subtler, but can degrade the sound quality of every one of your recordings if you don't spot it. If any signal gets accidentally routed back to itself, it may emit an obvious howl of feedback that no-one could possibly miss. However, if the routed level is low, it may pass unnoticed, but still add a flanging effect to your audio recordings. Once again, the best thing to do is explore the routing options of your mixer, and make sure that you know exactly what each control does: you will normally get the cleanest recordings if you mute every signal source but the one you are actually recording.
4. What's the best way to set up soundcard recording levels?
In general you just need to watch the level meters included in whatever software you are using for recording purposes, making sure that you get as high a level as you can manage without ever running into clipping. When you are recording 'live' inputs on acoustic instruments you will have to allow a reasonable margin for unexpected peaks (depending on the type of instrument this might be 10 or even 20dB). However, where signal levels are predictable, you can optimize recording levels far more to squeeze the last drop of dynamic range from your soundcard.
For instance, many people still predominantly use MIDI sounds, but then use the audio facilities of their sequencer to make the final master recording from the stereo output of their hardware mixer. You can take advantage of the fact that there will be no unexpected surges in level by playing back the entire song from start to finish while monitoring the soundcard input level: on most sequencer level meters this will then give you a readout of the highest peak level reached during the entire song. You can then adjust either your hardware mixer output level or soundcard input gain accordingly, to ensure that the track peaks at between 1 and 2dB below full digital level. For instance, if your peak meter reads –6dB by the end of the song, you can increase the input gain of your soundcard by 4dB (many are now calibrated in dBs), so that when you make the final recording it will peak at about -2dB. This will ensure that your recording makes the most of the dynamic range of your A-D converters.
If your soundcard has a dedicated DSP mixer of some description, there may be several gain controls at different points in the signal path. In this case you might start hearing distortion in your recording long before the signal level hits the top of the level meter. You may even find it impossible to get your input signal to reach the top of the meter display at all, since it is clipping earlier in the signal path. The solution to this is exactly the same as when using a hardware mixer -- you need to set the input gain control to a suitable position to match the level of your input signal. In the case of a hardware mixer the PFL (Pre-Fade Listen) control lets you check the setting of the input gain control in isolation, but this facility may not be available in your soundcard mixer. Check your soundcard manual (printed or electronic) to find the recommended way to line it up.
By the way, if your soundcard provides a dedicated mixer utility with its own level meters (such as Event's Echo Console), it may be preferable to monitor input signal levels with these rather than the meters inside your MIDI + Audio sequencer, as they are likely to suffer far less from latency, and thus be far more responsive and 'in time' with the input signal.
5. Can I ignore levels when recording digitally?
In general, yes, since when recording digital input signals the data should simply be copied bit-by-bit onto your hard drive. However, some soundcards provide a mixer level control for the digital input, so you should make sure that this is set to unity gain if you want to preserve the original signal. This often just means pushing the fader all the way up (to 0dB if there are any markings). The only reason you would want to alter this is in the case of cards like the Emu APS and SB Live!, which can mix all their input signals (including the digital ones) together. In this case a digital recording should be treated just like an analogue one, by watching the level meters.
Similarly, if a level control is available for a digital output, leave it full up unless you need to use it to set a monitoring level (for instance with external USB-connected digital speakers). Any position other than maximum will compromise signal quality by reducing its dynamic range, so try to avoid using such controls altogether if you can.
6. My soundcard can record at 24-bit resolution at 96kHz. Are there any special precautions I need to take?
It can be frightening to see how large your recorded files become if your soundcard has 20-bit or 24-bit converters -- both will occupy the same amount of space on your hard drive, and be 50 percent larger than 16-bit ones. If you move up to a 96kHz sample rate as well, the file sizes become three times the size of 44.1kHz/16-bit ones, and this huge increase in data flow will also mean that your computer will manage far fewer simultaneous tracks with the same hard drive. For this reason, some musicians with 24-bit cards but less powerful computers still carry on recording at 16-bit resolution to save space or achieve more audio tracks.
However, now that some audio software allows mixed file types (Cubase VST allows 16-bit and 24-bit files to be freely mixed, while Sonic Foundry's new Vegas Pro lets you mix files of different sample rates as well), you can mix and match a little more. Some sources, such as MIDI synths and samplers, may not warrant using more than 44.1kHz and 16 bits, because many only have 16-bit converters outputting 44.1kHz sampled sounds. However, if you are recording acoustic instruments or analogue synths, 24-bit recording may well give you better quality. You can save a lot of hard drive space and gain more simultaneous tracks by choosing a sensible resolution for each track individually.
Many of the latest 24-bit soundcards dither the 24-bit signal output from their A-D converters down to 16 bits, if you choose to record at that bit depth. If this is the case you are likely to get better 16-bit recordings than when only using 16-bit converters. However, if your 24-bit soundcard doesn't dither automatically, it may be preferable to initially record a 24-bit file, and then use a software dithering process to reduce this to 16 bits after the recording has finished.
7. How can I get the best performance from a soundcard with my chosen MIDI + Audio sequencer?
First of all, make sure you have the latest version of the soundcard drivers, since this will normally give you the best combination of features and performance. All manufacturers keep the latest updates on their web sites for free download, but even if you're not on the Internet, most UK distributors should be able to post you the latest drivers on a floppy disk if you ask them nicely. On rare occasions a new driver version may be released with a bug that wasn't in previous ones, but this will normally be speedily discovered by irate users. If you are concerned about this then wait for a week or two after a new release for the dust to settle before you install the new version -- by then the braver users (or the more foolhardy, depending on your point of view) will have published their findings on various relevant Internet forums.
