ToolMod Pro Audio
M/S Mastering Equalizer TM133

fully parametric 4- Band M/S Mastering Equalizer

The TM133 M/S Mastering Equalizer is not an equalizer in the original meaning. Unlike the TM204 Stereo Mastering Equalizer, the TM133 uses 4 fully parametric eq bands for frequency dependent regulation of the stereo base width. If offers sophistaced control of the spatial image of a stereo mix with less problems with mono compatibility than using the frequency independent base width control of the M/S Matrix TM130. Base enhancement in certain frequency bands, defined by the center frequency and q-factor controls, is possible without influecing the frequency response of the mix.
  • 4-Band M/S Mastering Equalizer
  • separate Boost/Cut Controls for M & S
  • Boost/Cut Range
    8 dB
  • Input L/R to M/S &
    Output M/S to L/R
    Matrix integrated
  • can be used with
    L/R or M/S Input
    and Output Format
  • 4 fully parametric Equalizer Bands
  • Q Range from
    3 oct. to a third
  • Low 20 Hz - 1 kHz
  • Mid1 50 Hz - 5 kHz
  • Mid2 0.2 - 15 kHz
  • Hi 0.4 - 25 kHz
  • Custom Boost/Cut and Sweep Ranges possible
  • Headroom + 30 dBu
  • Dynamic Range
    124 dBA/120 dBRMS
fully parametrich 4-Band M/S Stereo Equalizerfully parametric 4-Band M/S Stereo Equalizer TM133 with +/- 8 dB Range
The Principle
Widening the stereo base width is a powerful method for mastering and mixing. While frequency independent enhancement of the base width of the stereo image is effective but will require an elliptic equalizer to maintain a stable, centered bass range, frequency selective base enhancement offers an advanced method of analog audio processing. Focussing the base widening to certain frequency bands makes possible to achieve width and depth of the stereo image that is not possible with the linear method that is used in the M/S Stereo Direction Mixer TM130 and reduces the mono compatibilty problems related to the method as well as the need for extensive use of the elliptic equalizer. Here is some basic information on M/S Equalization.

M/S Equalizer Features
The M/S Mastering Equalizer TM133 has all necessary features to achieve the best possible results. Four fully parametric M/S equalizer bands with calibrated, separate boost and cut controls for the M and S channels are combined with a L/R to M/S matrix at the input and a M/S to L/R matrix at the output. The TM133 can be used with standard L/R format stereo input and output signals as well as M/S format signals. Matched controls for the center frequency and the q-factor for M and S with handpicked pots and q-factor matching for compensating the equalizer effect but still get the base width enhancement make possible use M/S equalization without hassles and without additional matrix units.

M/S Equalizer vs M/S Direction Mixer
The M/S Mastering Equalizer TM133 is no replacement for the TM130 M/S Direction Mixer. Although both modules can be used stand alone, the universal solution is a combination of both units. Using the elliptical equalizer in the matrix offers an easier and faster way to maintain a stable bass range - for vinyl production this is a must. With mixes in combination with a M/S equalizer, the frequency independent base width control of the matrix is usually used to reduce the overall base width after the frequency dependent base enhancement has been optimized. This will improve the mono compatibility. Since any base width enhancement can result in a level difference between left and right, the DIR pot (direction control) of the M/S Direction Mixer is another necessary tool to match the stereo channels after M/S treatment.
Center Frequencies and Q-Factor
All bands are implemented using adt-audio's fully parametric. active 'Vienna Bridge' circuitry that combines the sound performance of a passive LC filter with the flexibility of an active equalizer. The circuit works free from harshness and distortion and remains muscial with all settings.

  • Center Frequencies and Q-Factor
  • Boost & Cut
The q-factor range of all band is the same and ranges from 3 octaves down a third. The sweep ranges for the center frequencies cover the entire audio band with huge overlaps. The LOW band starts at 20 Hz and ends at 1 kHz. With a range from 50 Hz to 5 kHz the MID1 band can be used in the bass range as well as for the entire mid range. With MID2 from 200 Hz to 15 kHz and HI from 400 Hz to 24 kHz, the frequency band from 400 Hz to 5 kHz is covered by three eq bands in total. See 'Custom Versions' for different ranges.
The standard range of all boost/cut pots is +/- 8 dB. See 'Custom Versions' for different ranges. All eight boost/cut controls operate base width related; right-hand rotation increases the base width while left-hand rotation reduces the base width. The 'M' pots affect only the M channel while the 'S' pots affect the S channel.
Getting started with M/S Equalizsation
To get a first idea how the M/S equalizer works, just set the center freqeuncy of MID2 to approx. 4 kHz and the q-factor to the center position. Now turn the S pot of MID2 to the right to increase the base width. Tune frequency and q-factor for the best possible effect. Now switch the eq off and on to check the difference. With a standard mix you will get a combination of some improvement of the stereo image with some audible equalizer effect. Turn the M pot to the left to compensate the audible eq effect. The dB value for the M channel for the compensation is smaller than the boost value of the S channel. It depends on the base width of the mix. Check by ear for the best compensation. Since the compensation reduces the base widening a little, it is a good idea to adjust a small overcompensation and use the S pot again to go back to the previous enhancement.
Centering the Bass Range
Instead of using the elliptic Equalizer in the TM130 M/S Direction Mixer to center the bass range - which is definately the easiest and most effective way to maintain a stable 'bottom' of the mix - the low band of the TM133 M/S Equalizer can be used like explained here:

Set the center frequency of the LOW band to approx. 80 Hz and the q-factor to the three o'clock position. Set up a boost of about 5 dB by turning the M pot to the LEFT. Now turn the q-factor pot to the left as long as the boost is wide enough to cover the entire bass range. Reduce the boost to about 3 dB. This setting forces the bass range to the center but also produces a 3 dB bass boost.

Turn the S pot to the left to compensate the bass boost, overcompensate until you hear a small bass cut, and use the M-pot again to adjust a linear frequency response.

Try to modify this setting in little steps to get an improved result.
Input & Output Matrix
To use the TM133 M/S Stereo Equalizer in M/S mode, a format conversion from the common L/R stereo format to the M/S format at the input and a reconversion of the processed output signal from M/S to L/R is necessary. Since these matrix stages are integrated in the module, the M/S equalizer can be used with standard stereo signals in L/R format without the need of additional, external matrix stages.

  • Controlling the Matrix
  • Options
  • Stereo Operation
The rotary switch MODE controls the internal input and output matrix stages. Since the input and output format can be switched in and out it is possible to integrate the module into a M/S processing chain with several M/S modules.

The MODE switch determines the input and output format. In the L/R position, both matrix stages are active and the input and output format is L/R. IN selects operation with M/S input and L/R output format, while OUT selects L/R input and M/S output format. I/O bypasses both matrix stages and selects M/S format for input and output. The blue MODE-LED indicates any format selection but L/R for input and output.

With the standard factory setting, the bypass switch is a relay hard bypass that affects the M/S equalizer and the input and output matrix stages. This setting is practical if the module is used either with L/R or M/S input and output signals. If the module is integrated in a M/S processing chain, e.g. in combination with the M/S Mastering Compressor TM132, and either the input or the output of the M/S equalizer is used to convert or reconvert the format from or to L/R, the standard setting of the bypass switch results in an unwanted format conversion. The alternate setting keeps the matrix stages always in the signal path and the bypass switch only affects the M/S equalizer. However, the matrix switch is always functional and can be used to select the input and output format. The setting can be changed by jumpers at any time.
If the mode switch is in the I/O position but the input and output format is L/R, the equalizer operates in stereo mode - which is not intended or really useful but possible; e. g. for generating a pseudo stereo signal from a mono source. In this case the boost/cut pots for the M channel affect the left channel and the boost/cut pots for the S channel affect the right channel. Please note that due to the base width related orientation, left-hand rotation of the M pots results in boost while left-hand rotation of the S pots results in cut.
Custom Versions
Custom boost/cut up to +/- 20 dB and custom center frequency sweep ranges up to 1 : 100 are possible within about 2 weeks from order due to our rapid manufacturing shop
Headroom & Dynamic Range
The headroom is + 30 dBu throughout the entire M/S mastering equalizer. At linear settings with M/S input and output format, the output noise is less than -90 dBuRMS / -94 dBA, which results in a total dynamic range of at least 120 dBRMS / 124 dBA.

The TM133 is a 4U ToolMod module that fits into two slots of the horizontal 1U high ToolMod Frames. The vertical version fits into a slot of a 4U high ToolMod Frame.

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Price: € 1340.00
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ToolMod Frames
Test Reports
TM133h - horizontal
TM133v - horizontal
M/S Equalizer Basics
technical Specifications
Control Elements
Picture - h-Version
Picture - v-Version
ToolMod Manual
M/S Mastering Equalizer vertical VersionTM133 vertical
vertical Version

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