Preparation and Setup
Before you invest a lot of time recording music, you need to make sure the components that are being used are setup properly to minimize noise during the recording process. Since a majority of the time spent digitizing records is associated with the just playing the record, it’s critical that the turntable and the phono cartridge are in good condition. If the turntable hasn’t been used much in recent years, you might want to consider investing in a new drive belt and a phono cartridge. Two Internet stores that specialize in audio turntables and associated components are; Needledoctor and LP Gear. Note that if a new cartridge is purchased, find out how long you should break in the cartridge before recording your music, so you get the best music quality.
The figure below illustrates how the turntable, stereo amplifier and the sound card in the PC are wired together. The turntable is connected to the phono input of the amplifier. Note that a “phono” input must be used to allow the amplifier to boost the lower bass tones (i.e. RIAA equalization). If some other input is used, the bass frequencies will not get restored and the music will sound tinny.
The audio output from the amplifier (using tape/record output) is connected to the Line In connector of the PC sound card, which is usually blue in color. If the sound card uses mini-jack connectors, an RCA to Mini Jack converter cable will be required.
To achieve the highest possible recording quality, it’s important to prevent the electrical noise sources from being injected into the audio signal that is being recorded. All audio cables that are used to pass the audio signals between components, should be shielded to minimize noise. The other primary source of electrical noise is ungrounded or poorly grounded electrical outlets. Also make sure the turntable is grounded to the amplifier as shown above. Although the raw recorded file will be processed to remove unwanted noise, it is always best to prevent noise from being recorded, since noise removal techniques cannot perfectly discriminate between music and noise.
Once the recording hardware and software is configured, Sound Forge can be used to measure the level of background noise that is present to see if the hardware is properly connected. (Review the Recording section below for proper setup.) This is done by recording a short interval (i.e. 5 to 10 seconds) of silence with the turntable and amplifier powered on. Once the short sample is recorded, the Sound Forge Statistics function can be used to measure the RMS noise level, which gives an indication of noise loudness. Since the signal-to-noise ratio of a vinyl record signal is about 60 dB, the measured noise level should be less than – 70 dB. If the noise value is considerably larger (i.e. a number between 0 and –69 dB) the cabling and grounding interfaces should be checked and improved if possible.
Recording
Before recording with Sound Forge, a number of audio settings must be initialized.
If an M-audio or other high quality sound card is used, be sure to use ASIO audio drivers that come with the board. Then select ASIO for the audio device type in Sound Forge to achieve the best recording and playback quality.
Recording bit depth should be initialized to 24-bits so that all audio processing is done using higher resolution before down converting to the final 16-bit format.
The sampling rate should be set to 44,100 Hz. Higher rates are supported, but it's my experience that higher sampling rates don’t provide any discernable improvement in final audio quality. Also, since digitized files captured at higher rates will be larger, the amount of time to process the audio data can increase significantly.
The number of recording channels should be set to “Stereo”.
The Sound Forge record mode should be set “Multiple takes (no regions)”. This mode will result in a single recorded WAV file, even if at any time recording is stopped and then restarted during a recording session (e.g. between tracks).
Due to imperfections in the sound card hardware, the recorded audio signals may not be symmetric to the zero axis. This signal imperfection, known as DC offset, should be removed to prevent errors during audio processing. To eliminate this problem, the Sound Forge DC Adjust feature should be selected and calibrated. Since the DC Adjust calibration step only takes a couple seconds, I would recommend doing this each time a new recording session is started.
The last parameter to setup, prior to recording, is the audio input volume level. The input volume level needs to be set such that the recorded audio level never exceeds 0 dB. Any signal larger than 0 dB will be clipped, which will cause the recorded music to be distorted. To provide some clipping margin, the input volume level should be adjusted such that the loudest recorded music does not exceed –6 dB. Since the volume levels indicated by the VU meters are averaged signals, the –6 dB level provides margin allows for short, high volume sounds to be recorded correctly without distortion.
Once all of the above setups completed, the actual recording process is relatively simple. To record all tracks on a single album:
- Place the cleaned record on the turntable and start the turntable.
- Activate the Sound Forge "Record" button.
- Queue the turntable stylus onto the first track.
- When all of the tracks on one side of the record have been recorded, push "Stop".
- After turning over the album onto the second side, push the "Record" button again.
- Then queue the turntable stylus onto the first track of the side two of the record.
- When all tracks have been recorded, push "Stop".
- Once all tracks are recorded, the Sound Forge “Record” dialog box can be closed. The two recorded channels that are displayed in the data window, are now ready for processing.
Make sure you monitor music recording when queuing the stylus, to make sure recording starts properly. Don’t worry about “dead” recording time that may occur if recording is unattended, since these sections can be deleted later during audio processing.
After recording an entire album, you will have a file that is about 15 MB for every recorded minute of music. So for a 50 minute album, the file will be about 750 MB. If at this point you want to save the file and finish the digitizing process at a later time, save the file in a standard Microsoft WAV formatted file.
