Tantek's Tanrak system offers a whole host of audio processing units in a convenient custom-built rack. In the first instalment of a two-part review, we examine some of the modules available, assess their usefulness, and find out if they're good value.

So many women and so little time. Sorry! So many units and so little space. The mind does tend to wander at times. The problem is intrinsically the same, however: how to fit them all in. Less of the Waughle and down to business, I guess.

Tanrak is a 19-inch wide, 4U-high sub-rack which can house up to 11 plug-in modules plus a DC power supply. The rack is aluminium with a textured black stove finish. The modules themselves have anodised grained front panels with orange switches and lettering. When you're spending a few hundred pounds on your studio, it's nice to get something attractive as well as functional, and the Tanrak range certainly looks impressive. Very professional.

For those handy with a soldering iron, the modules are available in kit form at a saving of between 20 to 35 per cent. The kit parts are the same as those used in the finished modules, and they look very easy to build - though I speak as one who hasn't actually put soldering iron to PCB. If you do run into difficulties, Tantek will put right your mistakes for a standard charge of 20% of the kit price, which seems a very fair deal.

Just a few more words about the nature of the rack and the modules before plugging them in and working them out. The whole Tanrak system has been designed to be flexible. A bus on the back of the rack distributes power to the modules and interlinks the audio lines so you can rearrange the modules' positions while maintaining connections. Each module also has its own set of quarter-inch jack sockets at the back, and the rear PCB houses a Key bus. All modules have been optimised for operation at -10dBv but should operate just as well at 0dBm. It handled all my home studio equipment with ease.

The manual suggests five different ways of connecting the system:

1) Put a signal in the left-hand module, run it through the units and take the output from the right hand module. Individual modules can be switched out so the signal need not run through every one.

2) Using the optional Input and Output modules, perform option 1 from the front panel.

3) Use the rear sockets as a patchbay. While this is certainly feasible, you'd need easy access to the back of your rack. Difficult if it's tucked away neatly in a corner.

4) Extend the rear sockets to a patchbay. This obviously gives you ultimate control over the units but the smaller studio, particularly the one-man kind, will probably be able to manage quite well with option 1 or 2.

5) Use a Mixer module and run the outputs from certain modules onto the stereo virtual earth bus, extracting them with the Mixer, for example, to combine the outputs from several Mic Preamp modules. To do this in stereo, you'd need two Mixers. I never actually had the urge to do this during the review - apart from the fact that I wasn't supplied with a Mixer - but the option is there, and you may just find a problem or two which this method of combination and separation solves, especially if you want to work in stereo.

That's the introduction over. If you've scanned ahead to see how much the system costs, you'll want to know how Tanrak performs. Read on then, gentle reader.

Mic Preamp

Surrounded as we are by mountains of electronic instruments, it's easy to forget the human side of our music - the vocals. I plead guilty, too. As in life, nothing is easy and the best mics are the ones which need a little help to get up to line level. The Mic Preamp does this - and a little bit more.

The basic module provides a 12V power source which will suit most microphones, but it can be set to provide 24V or 48V via the Phantom Power module if necessary. It accepts a balanced XLR input and boosts it to line level. Unbalanced mics can be used, too, by making up an XLR-to-jack lead.

A Sensitivity control adjusts the gain, and an LED shows when it reaches 0dBm, but this is just a guide as you can crank the gain up further. If you do get headroom problems, the -20dB Pad can be switched in to help. Thoughtful stuff.

Up to nine Preamps can be used (eight if you use the Phantom Power module), and the outputs can be collected by two Mixer modules. The Mix control on the Preamps determines their level in the mix, while stereo position is set by the Pan control. The Phase Reverse switch ensures you don't have to spend hours re-wiring plugs because some wally (probably you) wired them up wrong in the first place. We've all done it.

The module also has an Effects Send and Return, so you can plug it in and out of anything else that might take your fancy. In a multi-mic setup, you could even give each Preamp its own EQ module. The permutations go on. And so must we.

Input Module

This gives you front-panel access to the rack. A stereo jack socket and a Key bus input save you messing around at the back of the unit, but all the inputs and outputs are there should you need them. Ten LEDs give a visual indication of the level, which can be boosted or cut. External inputs can be applied to the unit to check levels (now why didn't I think of that?). It really is a boon, being able to check and boost some bits of computer-related music paraphernalia. It's when you get to play with units like these that you realise how useful they are.

The input impedence is 1Mohm, so you can plug just about anything into it. I ran it through my gamut of input busters - and it didn't. Great for DI'ing a bass and other awkward instruments. As with the other modules, it passes its output to the module on the right, eventually ending up at the...

Output Module

This collects the signal from the module to the left of it and offers a handy output from the front of the rack along with stereo headphone monitoring. The line level output is only in mono, but there are stereo ins and outs at the back as usual.

To compliment the Input module, this has a very low impedance (less than 0.5ohms). Impedance matching is rarely an insurmountable problem in the smaller studio, but these two units should be able to handle most eventualities.

The Input and Output modules are not essential to successful processing, but they do make it easy to route a signal through the rack. You could even patch them into your mixer's send and return.

Pro-Gate

This is in fact a noise gate, though Tantek's literature makes a point of not using that phrase in describing the module, mainly to stress its creative uses. Noise gates are often used to control the spurious noise (usually of the white variety) produced by every kind of electronic instrument, the sort of noise which lingers in the background when no notes are being played. You never notice it live, but in the studio, it can make it sound as though your gear's acting up.

A noise gate, if you want to be technical about it, is an amplifier whose gain is unity when the input level is above a pre-selected threshold level. In other words, it monitors the input signal and cuts it off if it falls below a certain level, effectively preventing low-level residual noise from reaching the output.

Applications include keeping an instrument's output silent when it's not playing, and preventing extraneous noises filtering in through microphones. These gates can be a godsend when miking drums, and are handy to have around when someone turns up with a noisy amp and refuses to be DI'd.

The Pro-Gate has been optimised for operating levels of -10dBv (the Input module can adjust levels, should it be necessary) and has variable Attack, Release and Hold controls. The Threshold ranges from 0 to -60dBm, and should be able to handle anything you throw at it.

In the creative department, you can switch in an input from the Key bus so, for example, you could make a bass track follow the bass drum for a tight sound. The controls need to be set carefully to avoid a glitch when the gate switches off abruptly, but that bit's up to you.

Having a gate 'in the system' means you can channel signals through it automatically, and it even helps cut out the noise on digital synths.

Compressor-Limiter 2

Another useful and at times indispensable unit. A compressor reduces the dynamic range of a signal by progressively attenuating the level as the signal gets louder. A limiter reduces over-the-top signals, too, and is frequently used to prevent the odd peak getting into the system where it might over-saturate a tape. It can be a great help when recording vocals, especially when they're performed by singers with little mic technique, and it will also control a signal (from a guitar, say) in which certain harmonics or notes tend to peak above the rest. Both help get 'more signal' onto tape.

Compression is normally in the range of 3:1, so that a 3dB increase at the input would result in a 1dB output level. Limiting, on the other hand, is commonly in the range of 20:1. In both cases, there's a threshold level below which no attenuation takes place.

The Tanrak's Comp-Lim 2 has an adjustable Slope control, giving compression or limiting from 2:1 to 20:1. An LED glows from green to yellow to red to indicate the level of compression taking place. The unit has variable Attack and Release controls and a Key input.

Apart from the sort of merely practical applications discussed above, the unit can be used in an envelope-shaping capacity for creative effects, such as extending decay times and making sounds more percussive. It was easy to use and did its job well.

Infinite Flanger

I like effects units. Even with the almost infinite variety of sounds modern instruments can produce, there's still nothing like putting your latest creation through an effects unit. Flanging is an old effect now, and I hope most readers will know what it sounds like because, as it's impossible to describe, I'm not even going to try.

The Infinite Flanger takes its name from its (nearly) infinite flange ratio, ie. the ratio between the shortest and longest delay times. Clearly, a lot of thought has gone into the design of the module. The dynamic range is rated at 103dB, and the unit has two Bucket Brigade Devices (BBD), one of which is set by a Shift control to produce an offset delay. The Regeneration control strengthens the flange effect, while Mix controls the mix between the original and the delayed signal. There's also an Antiphase function which hollows out the sound.

The flanger can be swept manually with the Man control, or you can plug in (at the back) the Modulation Oscillator or another CV source for automatic effects. I'd say an external modulation source is really essential to get the best from the unit, and you should consider the Modulation Oscillator (see below) as a more or less compulsory addition.

The Infinite Flanger kept me busy for ages. It produced everything from vibrato (used on pianos), phased vibrato (and phased vibrato with funny bits) to wild and whirling sweeps up and down the harmonic spectrum. As it doesn't have a utilitarian function in the sense that gates and compressors do, you tend to feel guilty playing with it for hours instead of doing something productive. Still, all in the cause of a review...

Modulation Oscillator

This produces a CV modulation (0 to 5V) which can be varied from a sinewave to a rising or falling ramp wave. It has two outputs with independent Depth control. It also has a switchable Key/CV input, which automatically adapts itself for either an AC key signal or a DC CV, permitting effects such as amplitude-dependent vibrato, or the creation of complex new waves by external CV modulation. A cycle can be triggered by a Key input such as that from a drum unit or a synth, and there's an Envelope Follower output, too.

The frequency range runs from 1 cycle every 30 seconds to 12Hz. On a dial ranging from 0 to 10, all the vibrato settings occur in the last sector, so tuning can be a little on the tight side.

The module can be used to control any CV device, but as I've said, it's a fine match for the Infinite Flanger just discussed.

Next month...

...I'll be looking at the rest of the Tanrak range, embracing such units as psychoacoustic enhancers and digital sampler-delays. See you then.