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Rebis Revisited

Rebis Modular Effects Rack System RA200 Series.

A look at some of the newer modules currently available for the Rebis rack.

If your signals won't behave, send them to the rack.

The Rebis RA 200 series modular effects rack system currently comprises around twenty five different modules. These range from three types of power supply and three different jack modules, up to such sophisticated items as the RA 224 Filter Gate. Some of the modules of this range were reviewed by HSR in the September 84 issue together with a description of exactly what is involved in a modular effects system. To briefly re-cap, Rebis offer a 3U (five and a quarter inch) high, 19" wide frame which will house up to seventeen modules. Only one power supply is required for the whole lot resulting in a saving of weight, size and price for each module over the more conventional system of 19" rack mounting effects.

Rebis are continually updating and expanding their range and reviewed here are another seven, modules to complement those in last September's issue of HSR.

RA 211 Timer

The Timer can operate in three modes, is accurate to 1/100th of a second in an hour and the read out is shown on four double seven segment LED displays, one for hours, one for minutes, one for seconds and the last showing tenths and hundredths of a second. It will count up to twenty-four hours and then roll over. A toggle switch selects the mode of operation whilst momentary push buttons are provided for Start/Stop and Reset.

In 'C' the clock runs continuously and displays the time reached each time the Start/Stop button is pressed. Mode 'P' adds on time progressively after each start cycle and is frozen during the stop phase. The third mode of operation, 'Z', shows the time lapsed between each subsequent push of the Start/Stop button.

The variety of operational modes available on the RA 211 should cover all your studio timing needs and armed with one of these there would be no excuse for turning out songs at anything other than the compulsory three minutes and twenty seconds standard Number One smash hit single length.

RA 215 Panner and RA 216 Dual VCA.

A monstrous variety of tricks can be accurately performed using this pair of modules. The programmable panner is capable of many subtle and unsubtle variations on a theme, but what it basically boils down to is a unit which can control the relative levels of two signals simultaneously. The outputs from this panner then cause the Dual VCA to perform the level changes on the input signals.

To list each control on the RA 215 and 216 and explain its function would not give a very clear indication of the overall capabilities of these two modules, so instead I will mention how these are derived using the units in question.

The timing of a fade at the end of a track can sometimes be quite critical. You have survived all the tricky switching of effects and level adjustments during the mix only to mess up on the smoothness of the fade in the final moments of your creation. Using these two Rebis modules the length and depth of the stereo fade can be programmed and put into action by the mere push of a button. The fade can also be reversed or continuously repeated automatically. By reducing the depth of the fade and increasing the speed, a tremolo effect can be created. By using just a few dBs of fade a smooth and repeatable ducking can be affected for voice-overs. A flyback switch is provided which can be used to make the level leap from one end of the fade back to the other instead of a smooth continuous cycle between the two extremes. Using this feature to flyback from the loud end of the cycle to the quiet end can produce an interesting slow attack, backwards tape type tremolo. These effects are all created with the dual VCA switched to Fade mode. It also has a Pan mode which is even more fun. A mono signal can be panned across the stereo field at any rate and to any position, either cyclically using the Run button, or as a one-shot using the Pan to and Hold button. The movement of this image is also represented visually on the RA 215 by a row of LEDs. The width of the pan can be set using the Range pot on the Dual VCA and the pan can be biased to either side of the stereo field using the Range switch on the panner. In the centre toggle position the pan swings either side of the centre image and when switched to either end position the pan swings between that speaker and the centre image. Using the 'Pan to and Hold' and 'Flyback' buttons, the image can be made to either jump or float from any position to any other position each time the button is depressed.

Introducing a second input signal, these modules will enable smooth, repeatable cross-fades to be accomplished. As one signal is faded, the second is brought up and the speed and levels at which this is done are fully programmable. The panner can be set to fade from one signal to another and then back to the first with each subsequent press of the Pan to and Hold button. The two signals can also be made to follow each other in and out, or stop at any point during the cross-fade, using the Run/Hold button. Using a pair of Dual VCAs would enable stereo cross-fades to be accomplished with guaranteed speed and smoothness.

The RA 208 Modulator, as already mentioned in the HSR September issue in conjunction with the Rebis delay system, can also be used to dictate the rate of pans and fades produced by the Partner and Dual VC. The RA 215 has a toggle switch to select either internal or external rate control. When set to external the RA 208 Modulator can be made to select not only the rate of fade or pan, but also the rate of change of fade or pan. This is easiest to describe by imagining an image panning from left to right and back again at a constant level but with varying speed. This effect can be introduced into a mix to provide anything from the mildly interesting to the thoroughly disconcerting!

A Gate for Every Field

Noise gates available for the Rebis modular effects system currently number five in total: one FET and one VCA noise gate, one incorporating a filter section, one combined with a compressor and one with an expander. The expander is still to be reviewed by HSR and the low down on the FET noise gate has been given in a previous issue. An appraisal of the other gates is given below.

RA 222 VCA Noise Gate

The RA 201 FET Noise Gate, reviewed some months ago, was found to perform well. The RA 222 VCA Noise Gate is a later introduction to the Rebis range and uses newer VCA technology as opposed to the FET based system of the RA 201. This provides even lower distortion and a lower noise gating action. The RA 222 offers a sensitivity control which adjusts the threshold at which the gate opens. The status of the gate is indicated by a red (closed) LED and a green (open) LED. The attack (the time taken for the gate to open) is variable from 25pS to 250mS and is fast enough at one end to let through all the punch of percussion and slow enough at the other to produce the bowing effect which occurs when the initial percussive attack on a sound is smoothed out, a sound which can be very effective when applied to guitar. Release time is variable from 5mS to 2 sec and is the time taken for the gate to close once the signal has passed below the threshold. The time between the signal passing below the threshold and the release phase coming into operation is called the Hold time and is variable from 20mS to 3 secs. The provision of the Hold control allows for some very clean, tight gating to be produced. An in/out bypass is also provided. Using a percussion track in the key input to control gating on a polyphonic keyboard part can result in some very effective chopping chord work. The 'Hold' control is invaluable here for controlling the length of each chop. Using the Release instead of the Hold in this case would produce a softer sound as a slower decay would take the place of the sharp cut-off produced at the end of the Hold cycle.

I have never come across a cleaner, more precise noise gate at this price, and it seemed equally at home with guitar level signals as at line level.

RA 223 Comp Limiter Gate

This is a compressor/limiter with noise gate combined. The control parameters have been whittled down to the bare essentials to provide a basic operating unit. The limiter and the gate can be switched in and out independently and the limiter can be switched between a 2:1 compressing action and 20:1 limiting action. A sensitivity control on the gate sets the threshold between -40dB and +20dB, a wide enough range for the vast majority of uses. The gate release times are variable between 40mS to 1.7 secs and the gate attack time is switchable from 50pS to 2mS. A key input is also provided to operate with an associated pair of LEDs which indicate 2dB and 10dB of compression. I would have preferred a threshold level control here rather than a gain control, although I suppose it is better to attenuate excess gain than to try and recover lost gain. The release time for the compressor/limiter, i.e. time taken for the level to return to normal after the signal passes below the threshold level, is variable between 40mS and 1.7 secs.

There is some very sound (no pun intended) design philosophy behind the RA 223. For every extra dB of compression applied to a signal the noise floor moves a little closer so having a noise gate already there in line to deal with the noise makes good sense. A rack of these would be especially useful as part of a PA rig. One on each of the microphone channels could keep spillage down to a minimum and peaks under control to help keep the sound clean and tight. For multitrack recording purposes, where you can often get away with only needing one compressor and gate at a time, it might be wiser to invest in separate units each of which would offer control over a wide range of parameters. Having said this, the very low noise and distortion figures for the RA 223 make it of high enough quality for any recording application and for those on a tight budget it could kill two birds with one stone.

RA 224 Filter Gate

The RA 224 Filter Gate is a very versatile piece of signal processing equipment. It comprises a highly selective noise gate coupled with filtering which can be used to tailor the response of the through-going signal or to act on the key input to provide frequency conscious gating. Two RA 224 modules can be linked together for stereo operation and a ducking facility is provided to enable voiceover functions to be performed.

Sensitivity, Attack, Hold and Release all cover the same ranges as the RA 222 with the addition in the case of the RA 224 of an Attenuation Control. This sets the level to which the noise gate shuts down below the threshold level. It can be adjusted to anything between 0dB and 90dB of attenuation. When Duck mode is selected for voice-overs the music signal is fed through the gate and a feed from the voice track is fed into the key input. When the voice is sensed at the key input the ducking action closes the gate on the music track. The Duck switch actually reverses the action of the gate and attenuates over the threshold level instead of under it. Without an adjustable attenuation level the music would be reduced to an inaudible level. By use of this control, however, just a few dBs of attenuation can be programmed to allow the voice to emerge clearly. A bypass switch is provided together with a side chain monitor button which allows the signal at the key input to be heard. There are also three LEDs provided to indicate that: a) the threshold has been passed, b) the gate is open, and c) that the gate is being held open by the Hold setting.

The filter section on the RA 224 provides a pair of 12dB/octave roll-off filters. The first is a low pass variable from 30kHz down to 150Hz and the second is high pass variable from 15Hz up to 3kHz. A filter switch selects whether the input signal or the side chain signal is filtered. The filter section can, of course, be used as EQ in its own right, but it becomes particularly useful in conjunction with the noise gate. If a split feed is taken from the through signal and fed into the key input it can then be listened to via the side chain monitor. The filter section can then be tuned in to accept only the wanted part of the signal and thus the gate is prevented from being confused by any signals outside its selected frequency range. In this way the gate on a tom mic can be prevented from opening for a stray cymbal crash.

The RA 224 Filter Gate seems to have just about everything you could want in a noise gate and what's more, it all seems to work very well.


Don't let the size of these Rebis modules fool you. They are all thoroughly well designed and capable of more than their size would lead you to believe. They are up to professional operating specifications, but could still be afforded by the home user due to the aforementioned advantages of modular rack systems.

There are a wide range of modules available in this RA 200 series with something to fulfill most outboard tasks. I used the timer module to time the writing of this review. The timer worked well - I'm afraid I did not - I was having too much fun playing with the panner.

Prices for the modules are as follows: RA 211 Timer - £103.79, RA 215 Panner - £105.97, RA 216 Dual VCA - £136.56, RA 208 Modulator - £77.57, RA 222 VCA Noise Gate - £97.23, RA 224 Filter Gate - £136.56.

For further information contact: Rebis Audio, (Contact Details).

Also featuring gear in this article

Previous Article in this issue

Akai S612

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The Art of Toys

Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.


Home & Studio Recording - Jun 1985

Donated & scanned by: Mike Gorman

Gear in this article:

Studio FX > Rebis Audio > RA200

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Review by Martin Sheehan

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> Akai S612

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