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The Spanner

Not as you may think, a device to tighten up your sound; in fact if you use one, the chances are that your mix will literally endup all over the place.

Developed by Electrospace, the same company who gave us the ingenious Time Matrix, the Spanner (short for Stereo Panner) is one of the most, if not the most, sophisticated automatic panning system currently available.

Two basic models are on offer, the SP1 and the SP2. Both provide identical control options, the difference being that the SP1 pans a single input between two outputs whereas the SP2 pans two inputs simultaneously between the two outputs but in opposite directions.

The pan rate and depth may be generated using the internal oscillator or may be derived directly from an external source of modulation (which may include programme material). Additionally - and this is where the clever design comes in - a threshold detector allows the input to pan the system hard over from one side to the other whenever the threshold is exceeded, a further refinement being the inclusion of a counter.

Any number between one and eight may be set up on the front panel, and the circuitry will then decrement the counter by one whenever the threshold detector is operated. After the preset number of events, the system will pan to the opposite side. This may sound a bit involved but it will all become clear soon. (Honest - Ed).


You probably don't need me to tell you that this is another 1U X 19 inch rack unit and, yes - it's black. The style of construction is however most elegant and the case is almost as deep as it is wide. Considering it's size, it really is quite heavy. By way of front panel design, the Spanner is very logically set out and the very pale yellow legend looks a lot better in real life than it sounds on paper.

The counter is set by means of a miniature thumbwheel switch (presumably for engineers with miniature thumbs) and the count is displayed by a seven segment green LED numeric display set into the panel. This is intended to be a fully professional piece of equipment and to this end, both the inputs and outputs are on fully balanced XLR connectors mounted on the rear panel. Transformerless electronic balancing is used for both inputs and outputs and ground lift is provided by means of a rear panel switch.

In order to maintain the highest possible signal quality, Aphex VCA chips are used as the gain control elements enabling an enviable noise and distortion performance to be achieved.


First comes the input level control, and as the review model is an SP2, there are two of these; one for each input.

The Aphex VCAs are, of course, voltage controlled and the next front panel control; Offset, introduces a DC offset into the system which effectively displaces the centre point of the sweep to the right or left by any desired amount.

In order to inform the user just what the sweep is up to at any given time, the spanner uses a nine segment horizontally mounted LED display which indicates the scan position. The centre LED is green with all the others being yellow except for the two extreme left and right LEDs which are red.


This next section is the sweep oscillator and it incorporates both depth and rate controls, as you would expect. However, it also includes a 'Symmetry' control which means that the left/right pan can be at a different speed to the returning right/left pan.

On the rear panel, there is a high impedance jack input labelled 'Mod/trig' and, when the front panel 'Mod/trig' switch is set to external, the pan may be controlled by a signal fed into this socket. The control voltage follows the amplitude of this external signal and the sensitivity is set using the 'Mod clamp depth' control; when this control is set to minimum, the effect is turned off. If the selector switch is set to internal, then the system follows the amplitude of the audio input.

In either case, the pan starts from a position set by the offset control and is limited by the signal amplitude and the setting of the 'Mod/clamp depth' control.

The actual direction of the pan is determined by the trigger section. Next along the panel is the 'Mod/clamp damping' control which operates a slow limiter acting on the control voltage. In practice this affects mainly the decay time (or time the pan takes to return to it's starting position when the trigger signal ends) but there is some interaction with the attack time. The handbook suggests that this control should be set at or near minimum for modulation effects and turned up only when in 'Clamp' mode which we shall be coming to shortly.

Clamp Mode

I told you I'd get to it shortly! When set to clamp mode, the output sits at one side, ignoring all modulation input until it receives an instruction from the trigger department, at which time it dashes to the opposite side as fast as the 'Mod/Clamp Damping' setting will allow it. The excursions of the pan may be constrained by altering the 'Mod Clamp Depth' control if extreme panning is not required. With minimum damping, a full pan takes around 250 milliseconds but may be slowed to a maximum time of 20 seconds if required.

Counting the Shots

The trigger count system is probably the Spanners main claim to innovation and may be activated by the audio signal input or by a signal fed into the 'Mod/Trig' jack, selection being made by means of the 'Mod/Trig' panel switch.

A threshold control sets up the trigger circuit in much the same way as a noise gate, and a red LED within the numeric display window illuminates whenever the threshold detector operates. To prevent unwanted multiple triggering, the bane of threshold circuits, a fast attack/slow decay time constant has been built in which inhibits further triggering until the signal amplitude falls below the threshold level at which time the circuitry is reset.

As the system includes an eight stage counter, the pan may be set to operate after a predetermined number of threshold crossings which opens up new avenues for creative synchronised panning. To further increase the flexibility of the Spanner when used in conjunction with other processors, the rear panel contains a trigger output jack which provides a nominal fifteen volt pulse whenever a polarity change (pan) occurs. The counter itself is reset using the front panel 'reset' switch.

In Use

Despite it's apparent complexity, the Spanner is quite easy to get used to and it's lots of fun. Even simple effects such as panning a reverb or echo return signal can be very impressive when tastefully used and a heavily panned keyboard can sound almost as though it is being played through a Leslie Tone Cabinet. Asymmetrical panning can sound somewhat disorientating at first but there is a place in art for everything.

By using the sound source itself to imitate the pan, some interesting, almost random panning effects can be set up and the result can end up like being on the Octopus at some amusement park after a gallon of lager and one kangaroo vindaloo too many. The great thing about this system is that you can see whats going on at all times courtesy of the 'Knight Rider' display and it's even possible to deliberately clip the panning waveform by simply using too much depth or offset in the LFO department, so that the signal in effect waits in the wings ready for the return sweep. I particularly like the effects that can be created using the external triggered sweep and it is easily demonstrated using a drum machine and an arpeggiated synth synced together. By using the programmable trigger output on the drum machine to initiate a fast pan, the synth can be made to appear stereophonic with certain notes coming from the left and others from the right.

If you use a real drum kit (and I didn't try this) it is apparently possible to use the drum beats to operate the threshold circuit which then drives the counter circuit causing the signal to pan every time a predetermined (up to eight) number of beats is detected. This could be used to pan the sound of the drum kit itself or it could be applied to another instrument or effect within the mix.


Suffice it to say that the Spanner is capable of creating just about any panning effect that you can dream up without compromising the signal quality in any way.

A panner usually comes pretty near the bottom of most peoples equipment shopping list as there are other more basic devices such as compressors and gates that have to be bought first, but if these can be considered as the bread and butter of recording, then this panner must be the icing on the cake. Being as sophisticated as it undoubtedly is, the Spanner isn't the cheapest panner on the market, but at £450 + VAT for the SP1 and £540 + VAT for the SP2, it isn't really expensive considering what it has to offer. Distribution of the Spanner is being handled by Britannia Row, where several Spanners have already found their way into the hire department.

For further details contact Britannia Row, (Contact Details).

Previous Article in this issue

Hot Rodding an MM Mixer

Next article in this issue

Teac A-3440

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


Home & Studio Recording - May 1985

Donated & scanned by: Mike Gorman

Gear in this article:

Studio FX > Electrospace > The Spanner

Review by Paul White

Previous article in this issue:

> Hot Rodding an MM Mixer

Next article in this issue:

> Teac A-3440

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