Transmission Zero

Introduction

I wrote this, with my article about connecting your decks to your computer in mind. It can however, be used for any line level audio source connected to your computer i.e. a radio, TV, cassette recorder, MIDI keyboard.

Foreword

If any of your equipment is under warranty, you may want to check to make sure that connecting it up to other equipment doesn’t void your warranty. From what I have experienced, sound cards are fairly tough devices. Don’t tempt fate by doing anything silly with them. Remember, always start with the output volume of the equipment you are connecting to the computer, at zero. Then raise it slowly to make sure you aren’t overloading the sound card. As long as you follow these rules, you shouldn’t be in any danger of causing damage.

Requirements

You will need some audio recording software. If you don’t have appropriate software (Windows Sound Recorder isn’t really appropriate for the job), you can download a shareware program called GoldWave. The unregistered version features nag screens, but is fully functional, and well worth purchasing. Alternatively, Audacity is a popular open source audio editor, and can be used in Windows, Linux, and Mac OS X.

This editorial uses GoldWave, although any good audio editor should be very similar to use.

I am also assuming that your audio source is connected up to your computer. If you need help with this, then please take a look at my other editorial on connecting your decks to your computer (most of which can be applied to any line level audio source).

Setting Up

Open the device controls window and click on the “properties” button located directly beneath the “record” button. The properties window should come up. Click on the “record” tab. Check the “monitor” check box in the “recording options” section. Monitoring the input allows you to set the volume accurately before recording, which will help minimise the chances of your audio clipping. Now go on to the “volume” tab. Select the approprate check box and make sure none of the rest are checked. Unless you are recoring from a passive microphone, then you will want to be using the line input. The volume should be set to about 50%. Click on “ok”.

Creating A New File

Go to “file—new” in GoldWave’s menu. You will be presented with various options for the quality of the recording. I would recommend using the CD quality setting—16 bit stereo at 44 100 Hz. The length should be set to the required length of the recording, plus a little extra to be on the safe side. Click on “ok”, and you should get a new window with a silent wave file.

Starting Your Audio Source

Start the audio source which you want to record from, with its volume right down. Gently raise the volume of your audio source. You should see the sound starting to appear in the “device controls” window. If it doesn’t, then please check your previous steps to make sure everything is working properly. Raise the audio level, so that the red LEDs in GoldWave’s window start to light during the loudest part of the audio.

Avoid Clipping

Clipping happens when the dynamic range of your audio source is larger than the A–D converter in your sound card can represent, i.e. you have the volume too high. The peaks in your sound will be flattened. In small amounts, clipping is not too noticable. If the clipping is more severe, the sound will start to sound very fuzzy. Even with unoticable amounts, it is bad practice to allow it to happen. Having said that, even the professionals seem to let it happen sometimes!

On the left, you can see the tops of the waves are flat. This is something you really want to avoid. The example on the right however, is an example of the audio levels being just right. If anything, you want the audio levels to be a bit lower than needed, because you can maximise the volume after you have done the recording.

Recording

Now you have set up everything, all you have to do is hold “shift” and press the “record” button. The shift key is a safety measure, which helps to prevent you from accidentally overwriting a previous recording. Now GoldWave is recording, you can start your audio source. Similarly, when the audio source has finished, you can hit the “stop” button.

Now is a good time to save your work, in case anything happens to go wrong while you are editing! Unless you are short of hard disk space, it’s best to save your work in an uncompressed format, such as a “wav” file. If you do save it in a compressed format, you should make sure you use a lossless format (i.e. not mp3), because you will lose audio quality each time you save the file. A good lossless audio codec is FLAC.

You can now edit your audio file until your heart is content, knowing that if you mess things up, you can simply revert to the saved version. The most important thing you’ll need to do is trim the leading and trailing silence from the file. This can be done by placing the cursors either side of the silence, and pressing the “delete” key. Just make sure that what you are deleting, really is silence, and not just a very quiet passage!

Now you’ve finished editing the file, you can save it in a format of your choice. If you are sure you no longer need the full quality version of the file, you can now save your work using a lossy audio codec. This will save you a lot of space on your hard disk, at the expense of only a small loss in audio quality. One of the most popular and widely supported audio formats is mp3. I find a stereo recording with a sample rate of 44.1 KHz and bitrate of 128 kbps is acceptable, but some people go for 160 kbps, 192 kbps, or sometimes even higher. I personally recommend Ogg Vorbis, which produces excellent quality audio files at high compression, and is also free from software patents.

Other Features Of GoldWave

Gold Wave is a very fully featured wave editing program. There is too much for me to cover here, but it is worth having a look through its documentation to find out what else it can do.

If you have plenty of RAM on your computer, it may be worth looking in the documentation about RAM editing. This is a lot quicker than editing files on your hard disk. If you use the hard disk method of recording, then do have a look at the “unbounded” feature too. This allows you to record for an unlimited length of time (file system limits and hard disk space being the limiting factor).