Soft saturation

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Overview

The term "Soft Saturation" is used for a feature in Lavry AD converters, which is a form of digital signal processing that produces a result similar to analog tape saturation. However, it is not an attempt to emulate a specific type of analog tape.

The main application is for peak level control to allow higher average levels; or "hotter levels." Average level is more important in determining the perceived "loudness" than peak level.

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.

Update

The Lavry Savitr features an updated version of Soft Saturation. Please see the Savitr section (below) for details.

Basics

Types of Soft Saturation

Lavry AD converters have different types of digital soft saturation, depending on the model. Prior to the release of the Savitr AD-24-200, there were two types of Soft Sat. The following does not apply to the Savitr:

  1. "3dB" which has an effective threshold of "-6dBFS" and increases the level of signals below this threshold by 3dB.
  2. "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.

Functional differences

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.

Savitr Soft Sat

  • "2dB" which has an effective threshold of "-4dBFS" and increases the level of signals below this threshold by 2dB.*
  • "4dB" which has an effective threshold of "-8dBFS" and increases the level of signals below this threshold by 4dB.*
  • "6dB" which has an effective threshold of "-12dBFS" and increases the level of signals below this threshold by 6dB.*

(*)The gain applied is +/- 0.2dB of nominal value.

Functional Description

  • In the following examples the input level is adjusted with the SAT disabled so the signal peaks reach very near 0dBFS but do not “clip.”

The Savitr 6dB setting, 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 peak section of the waveform 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 Savitr, 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 can be 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.

The Savitr 2dB and 4dB settings provide more choice in the processing of music program compared to the 3dB version in earlier models. The nature of the processing is similar, taking into account the difference in threshold and gain.

Operational Considerations

  1. 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 loudness added to the program material once the digital gain is applied.
  2. 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 displayed 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 4dB setting of the Savitr Soft-Sat threshold appears at “-4” on the front panel meters because the -8dBFS threshold level is raised 4dB 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 -4 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.
  • The 2dB setting of the Savitr Soft-Sat threshold appears at “-2” on the front panel meters because the -4dBFS threshold level is raised 2dB 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 -2 on the meters.

Detailed Description

For more detailed information on the original Soft Saturation, please refer to Appendix III of the LavryGold Ad122-96MkIII manual which is available here

Lavry Products

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