When I think of signal processors, such as compressors and equalizers, I picture classic models with glowing arrays of tubes, chunky Bakelite knobs, metal

When I think of signal processors, such as compressors and equalizers, I picture classic models with glowing arrays of tubes, chunky Bakelite knobs, metal toggle switches, and large analog meters. Those were the kind of products I came in contact with when I started out in recording studios-too long ago to dare think about! Like many people, I'm working mostly from my home studio these days, where my chief "weapons" are Pro Tools and a Yamaha 02R.

When it comes time to master my projects, I could use the processors in my mixer or plug-ins from Pro Tools, but I find it is often better to deal with the final mastering as a completely separate stage in the production process. In a perfect world, I would bring in specialized tools for the job, such as the aforementioned classic tube devices, but vintage gear is extremely expensive.

So what's the answer? One solution is T-Racks from IK Multimedia, a company based in Modena, Italy. T-Racks is a stand-alone software package for Mac, Windows, or BeOS that emulates those high-end analog mastering tools. It includes a state-of-the-art 6-band parametric equalizer, a stereo tube compressor/leveler, and a multiband stereo limiter-all at an extremely attractive price.

Of course, you can get Pro Tools TDM plug-ins (or plug-ins in other formats) that offer most of these features, but the big difference here is that T-Racks gives you a dedicated environment for mastering. It boots quickly, loads a file in seconds, and lets you concentrate solely on the final stages of mastering. (For those who might be unfamiliar with mastering, it is the process of applying equalization, compression, and limiting to your mixes-balancing the volume, stereo imaging, and overall tonal qualities of each track to achieve proper continuity throughout the recorded project.)

THE USER INTERFACEOne of the striking things about T-Racks is the sheer simplicity of its user interface. It has only one screen, with a realistic-looking graphic depiction of a stack of analog processors replete with glowing tubes that change colors based on the number of individual components switched into the signal path. The processors provide the typical controls you'd expect to see, laid out in the usual manner.

I took a quick peek at the File and Edit menus, expecting to find software-related commands-such as loading and saving files, adjusting preferences, and so on-but I was surprised to find almost nothing there apart from Quit and Undo. It turns out that most of these items are spread around the T-Racks panels, disguised as input jacks, hidden under virtual LEDs, or discreetly available from a row of neatly labeled buttons referred to as the Console Strip. As a Mac programmer, I know that it would not take a lot of additional programming effort to put these commands in the menus where they belong.

More specifically, the Console Strip contains a horizontal row of seven buttons and a question-mark icon. On the far left are the Quit and Info buttons, followed by the Preferences button. Pressing Preferences opens a floating window where you can switch dithering and real-time processing on and off, set the audio-buffer length, and choose a color-gold, copper, or chrome-for the rack of virtual gear.

The next button, labeled Snap, brings up a floating window that lets you take up to eight snapshots of various processor settings. These can be recalled at any time, which is useful for comparing different settings on the fly during a song. The CPU button brings up another floating window for monitoring the degree of computer-processor activity. There's also an Undo button, which lets you go back one edit, and a Meter button, which opens another floating window with a large, high-resolution, sample-accurate peak-program meter.

Finally, the question-mark icon at the far right of the Console Strip is actually a Help button. Enable this function, and you can position the mouse over any of the controls to display appropriate explanatory text in the upper right corner of the screen.

At the bottom of the window to the right of the Console Strip is a set of transport controls with buttons for Stop, Start, Loop Playback, Return to Start, Jump to Next Marker, and Jump to Previous Marker. Loop start and end points can be set by dragging two small loop markers that appear on the time-line slider above the transport controls when loop playback is enabled. The positions of these markers are also indicated in the numerical display above the timeline.

An icon resembling a small input jack, labeled Mark, is actually a button that inserts a marker in a file at the moment you click on it. These markers let you quickly jump between various points, such as verse and chorus, using the Jump Marker buttons. Alternatively, the time-line slider can be dragged to quickly place the playback start point anywhere in the file.

Above the Mark button are two similar buttons, labeled Fade-in and Fade-out. Clicking on either of these opens a small floating window that lets you set the fade time and choose a logarithmic or linear fade curve. Clicking on the input-jack icons marked Open and Process loads and saves files, respectively. I guess this is a bit like plugging in your input and patching your output to your master recorder, but in this case you are opening a file and then processing it and saving the result.

Files can be previewed before loading, and presets can be applied to the audio file while previewing. This makes T-Racks very fast to work with. For instance, you can compare all the songs of a project-with their appropriate mastering settings-prior to processing.

THE MASTERING PROCESSORSTypically, you might start a mastering project by applying some equalization. The T-Racks equalizer has six filters that were specially developed for mastering: Low Cut, Low (shelf), Low Mid (peak), High (shelf), High Mid (peak), and High Cut. A set of on/off buttons and frequency controls for these filters is accompanied by gain controls for the shelving and peaking filters (+/-15 dB) and two toggle switches that select low or high Q for the two peaking filters.

A small numerical display shows the gain in decibels or the frequency in hertz or kilohertz of the currently selected knob, and it's easy to check how these filters are altering the frequency response by looking at the oscilloscope-type display to the right of the EQ section. A Patch switch lets you place the equalizer section either before or after the compressor in the audio chain.

The compressor, called Tube-Comp, can be used to make a mix sound louder, more cohesive, and more punchy. The usual Attack and Release knobs are available, and a Stereo Enhancement control affects the stereo width of the mix. This is not a conventional "threshold and ratio" compressor; it's very much a "soft knee" unit with a "no threshold" characteristic. Raising the input level increases the compression and vice versa. There isn't a particular level at which the compression begins; the Gain Reduction VU shows compression even at very low levels. This works like an old tube compressor, providing gentle compression that's ideal for mastering.

If you want to bring up the level of your mix even higher, T-Racks' multiband limiter can be used to tame peaks that occur in three different frequency ranges. The simplicity of the limiter's controls hides its complexity-which I reckon is a good thing. As the Input Drive control is turned up, it limits more peaks and increases the level of the program material. An "analog" VU shows the amount of gain reduction in decibels. Limiting is applied within three frequency bands, but they cannot be controlled independently. Consequently, the meter displays an average of all three.

As you might expect, the Release Time knob controls the time it takes the limiter to return to unity gain after peak limiting, but the Overload control is a bit less conventional in its operation. As this control is turned up, the limiter lets progressively more of the peaks through, which are then clipped in an analog-like fashion as would happen with a classic tube device-a neat touch.

THE OUTPUT STAGEThe Output section of T-Racks can be used to tweak the program material even more. To the right of the Output control knob, there's a three-stage (-3 dB, -1 dB, and 0 dB), stereo, LED-style level meter. Above it is another virtual LED, labeled Sat (for saturation), which indicates when clipping occurs. An associated toggle switch is provided for choosing between hard (digital) or soft (analog) clipping. If you don't want clipping, the Output control must be kept at a suitably low level. There's also a Bypass switch that allows for easy A/B comparisons between the processed and unprocessed audio. If the original mix has L/R level-calibration problems, the Balance control can be used to correc t them.

Above the output controls is the Preset display, which shows the name of the currently selected preset. Click on the preset name and hold it, and a pop-up menu opens with the factory presets, such as Brickwall Master, Gentle Master, Flat EQ + Hard Compression, Low & High Boost + Compression, and so forth. The menu also lets you save and load user presets.

Once all the desired processing has been determined, the results can be written to disk by clicking on the Process button. If Realtime Processing has been enabled in the Preferences menu, you will hear the new file playing as it is being written to disk, and further adjustments, such as recalling snapshots, can be made in real time. If no additional tweaks are needed, disabling Realtime Processing allows the file to be saved more quickly.

IN ACTIONI tested T-Racks on a Power Mac 9500 with a 300 MHz G3 upgrade, 192 MB of RAM, and Pro Tools 24 Mix audio hardware via Sound Manager. I started with a fairly dry recording of an acoustic Gibson L5 guitar solo. The track had been recorded flat using an AKG C12 VR microphone that emphasized some of the higher frequencies. While the track was still in Pro Tools, I had applied EQ to remove some of the boominess and presence boost, and I also added some gentle compression with the Waves Renaissance Compressor.

Then I opened the file in T-Racks and chose Gentle Master 1 from the excellent selection of presets. I found that it replaced some of the highs and lows that had been lost as a result of my previous equalizing. It also made the overall sound a lot punchier without emphasizing any boomy or scratchy frequencies-just what I was looking for.

To see just how versatile T-Racks was, I checked out an Alanis Morissette soundalike mix, which was packed full of acoustic and electric guitar parts, bass, kit drums, drum loops, synth sounds, and so forth. This time, I decided not to bother with the presets and just go for it by tweaking the knobs myself. The bottom end was a little heavy, so I started out using the EQ section to reduce some of the lower frequencies. The oscilloscope display really came in handy here, adding visual feedback to what my ears were hearing. I ended up just cutting a fairly narrow range of frequencies around 150 Hz by a little more than 1 dB. I used the Low Mid filter to get the effect I was looking for, rather than rolling off the low frequencies with the Low filter as I had first intended.

Then I decided that the bass and drums weren't sounding raunchy enough. This was a job for the compressor section. I used fairly fast attack and release settings (32 milliseconds and 320 milliseconds, respectively) and pushed up the input drive until the track really started to rock.

Not surprisingly, I found manipulating onscreen controls with a mouse to be more difficult than turning real knobs on an actual processor. Of course, that's always going to be a problem with software emulations of hardware products (mixers are a prime example). This problem would be largely eliminated if the software responded to MIDI Control Change messages from a MIDI controller box. However, it should be noted that sweeping through the frequencies with the EQ controls while the mix played back sounded just as smooth as the best hardware I have used.

THE LAST WORDT-Racks is a very straightforward yet powerful package of software mastering tools that does what it claims simply and effectively. I particularly like the user interface design, and I am quite impressed with the sonic results, which compared favorably to plug-ins costing many times more.

Music-technology consultant Mike Collins lives in London, where he plays guitar, writes and produces music, teaches music technology, and writes for music magazines worldwide.