Wave Corrector provides five different digital filters that can be used to correct deficiencies in either vinyl or tape/cassette source recordings. The filters can be applied singly or in any combination. The following filters are available.
Hiss Reduction: 8, 14 or 20dB
Hum Reduction: 20dB
Rumble Reduction: 20dB
Treble Control: -12, -8, -4, +4, +8, +12 dB
Graphic Equaliser: user defined equaliser/filter
Filtering is used for two principle reasons:
To remove unwanted nose components
To correct the frequency response of the recording
Of the filters available in Wave Corrector, the Hiss, Hum and Rumble filters are solely for noise removal and the Treble Control filter is solely for correcting the frequency response. The Graphic Equaliser, being user-defined is more versatile and can be used for both purposes.
The Hiss and Hum reduction filters use a special technique known as 'Noise Subtraction'. This method uses a 'noise profile' that represents the unwanted noise present in the file The noise profile is used to create a mask that is 'subtracted' from the entire file. Noise subtraction is very effective at removing unwanted noise whilst preserving the full range of frequencies in the underlying music. However, for the technique to be successful, there are some important precautions to be observed. See the topic Noise Profiles, for extra guidance.
The rumble filter is a simple high pass filter that removes the sub-audio frequencies below about 30Hz. Rumble is generated by some tone-arm/pickup cartridge combinations. When it is excessive, rumble can cause damage to loudspeakers so it is important to filter it out it you suspect its presence.
The hum filter removes the power line frequency (50/60Hz) and its harmonics. Like the hiss filter, the hum filter uses noise subtraction to help avoid removing too much of the musical content. However, you should only use the hum filter as a last resort. If there is hum present in your recordings, you should make every effort to isolate and remove the cause - usually incorrect grounding of one or more components in your recording set-up. Using the hum filter 'after the event' will inevitably lead to some degradation of music quality.
The treble control filter provides up to 12dB of treble lift or treble cut. You can experiment with this filter to obtain the optimum tonal balance from your vinyl, tape or cassette recordings. Cassette recordings, in particular, often need to be tonally corrected due to a mis-match between the Dolby-B pre-emphasis and de-emphasis characteristics. If you find that your cassettes sound too dull or too bright, you can correct them using this control. You may also find that you obtain good results by recording your cassettes with the Dolby turned off and using Wave Corrector's hiss reduction and treble control combination to correct the sound. Although this gives a theoretically false result, it can sometimes be more pleasing with some types or source material.
The graphic equaliser enables you to 'draw' a required frequency response with the mouse and have the filter applied to your wave file. See Graphic Equaliser for more information.