The term "Soft Saturation" is used for a feature in Lavry AD converters, which is a form of digital emulation of analog tape saturation. The main application is for peak level control to allow higher average levels; or "hotter levels." Advantages include no change to the signal quality below the "saturation threshold" and the absence of "attack and release" time constants found in limiters and compressors. The result is that compression or limiting can be used before or after conversion without the undesirable side effects caused by difference in time constants. The added benefit is that reducing the peak level can allow more aggressive use of compression, limiting, or loudness maximizing after the Saturation is applied.
Types of Soft Saturation
Lavry AD converters have two types of digital soft saturation:
- "3dB" which has an effective threshold of "-6dBFS" and increases the level of signals below this threshold by 3dB.
- "6dB" which has an effective threshold of "-12dBFS" and increases the level of signals below this threshold by 6dB.
- The LavryGold AD122-96 MkIII or MX models have two settings: "3dB" and "6dB."
- The LavryBlue MAD-824 has the "6dB" version of digital saturation (D-Sat) and analog saturation (A-Sat).
- The LavryBlack AD11 has the "3dB" version of digital soft saturation.
The LavryGold AD122-96 MkIII or MX models have high-powered DSP processing which produces the best results with complex audio such as a finished mix. Although the basic operation of the 6dB or 3dB setting is similar in the LavryBlue MAD-824 or LavryBlack AD11, the additional processing power of the LavryGold AD produces a more precise result.
The LavryGold 6dB setting and the LavryBlue “D-Sat” have a threshold of -12dBFS. Signal peaks above this threshold are reduced in level in a progressive manner so that signals just above -12dBFS are only slightly affected. As the peak level increases, the effect increases so that the level never exceeds -6dBFS. Digital gain is applied after this process to raise the over-all signal level by 6dB, so the peak level once again reaches 0dBFS at the digital output of the converter. This makes the 6dB version in the LavryGold and the D-Sat of the LavryBlue best suited to un-compressed or “large dynamic range” material. The advantage is that 6dB of gain raises the average level of the audio program significantly.
The LavryGold 3dB setting and the LavryBlack AD11 “Sat” have a threshold of -6dBFS, so they are better suited to processing compressed audio tracks or stereo program that is already compressed or limited (it has a smaller difference between the average (or VU) and peak level than uncompressed material). The gain added to the average level is 3dB.
- If the ‘Blue D-Sat or ‘Gold 6dB setting is enabled while feeding the AD high average level program, the audio can sound too distorted. This is because too much of the signal is higher than the threshold of -12dBFS. It is possible to lessen the effect of the Blue D-Sat or Gold 6dB setting in this case by simply reducing the level of the analog signal feeding the AD converter to control the amount of saturation effect. This also reduces the over-all level, so digital gain must be used after encoding to raise the peak level to maximum. If the input level is reduced by less than 6dB, there is still additional level added to the program material once the digital gain is applied.
- The front panel meters of all Lavry AD converters reflect the digital output level. Because the Saturation modes add gain digitally, the level of the threshold is also raised by the same amount.
- The 6dB setting of the ‘Gold and the ‘Blue D-Sat threshold appears at “-6” on the front panel meters because the -12dBFS threshold level is raised 6dB by the digital gain. By watching the front panel meters, the user can see how much of the music program is being “saturated” by looking at how often the level exceeds -6 on the meters.
- The 3dB setting of the ‘Gold and ‘Black AD11 Sat threshold appear at “-3” on the front panel meters because the -6dBFS threshold level is raised 3dB by the digital gain. By watching the front panel meters, the user can see how much of the music program is being “saturated” by looking at how often the level exceeds -3 on the meters.
For more detailed information, please refer to Appendix III of the LavryGold Ad122-96MkIII manual which is available here