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Boss CE-300 Super Chorus

Designed to complement the popular Boss DE-200 digital delay unit, the CE-300 employs a couple of psycho-acoustic tricks to produce an impressive stereo chorus effect. Paul White finds out just how impressive.

At first glance, you could easily mistake the CE-300 for the DE-200; both are 1U rack-mounting effects and both share the same colour scheme and general styling, even down to the ubiquitous block diagram on the cover. Technically however, the units are quite different, the DE-200 is a digital delay whilst the CE-300 employs state-of-the-art analogue delay lines to produce the relatively short delay necessary for the generation of chorus effects.

The overall size of the CE-300 is 482(W) x 47(H) x 246(D) which is, of course, in millimetres. For those of you who actually need to know the dimensions, it's 19 x 1⅞ x 911/16 inches! If the rear springs on your Transit are giving cause for concern, you 'll be relieved to learn that the weight is only 3.1 kg which is 7lbs, or near enough. For those of you who don't use a rack-mounting system, the mounting ears are removable (unlike Prince Charles').


Being a dedicated chorus unit, there are only five control knobs which can be most clearly seen on the line drawing.

The level of the single input is monitored by a five segment LED display and the control directly below this allows the signal level to be optimised - too much level will cause distortion whilst too little will worsen the signal-to-noise ratio. The effect on/off button acts as a bypass switch for comparing the untreated sound with the chorused sound.

To anyone who has ever used a chorus machine, the rate and depth controls will be familiar; as chorus is a cyclic effect, the main variables are the speed and depth of the effect.

The 'Direct Mute' cuts out that portion of the output signal that is derived from the untreated signal leaving only the pitch modulated component which is useful for creating true vibrato effects.

Next comes the section for modifying the level and tone of the pitch modulated component and this determines the tonal quality of the chorus sound and also the subjective depth of the effect. The level control is really a means of adjusting the balance between the dry and the modulated signals and setting up is done entirely by ear.

Being a stereo chorus, there is one input and two outputs, though if Output A only is used, the channels are combined to give a composite mono signal. All the front panel sockets are duplicated on the back panel and an additional socket is provided for use with an optional bypass footswitch.

The power switch, direct mute switch and effect switch, all have status LEDs but there is no flashing LED to indicate the modulation rate.

How It Works

To achieve a good signal-to-noise ratio (not quoted), compander-type noise reduction is used, compression being performed before the signal is split into two channels.

Each channel incorporates a similar delay line but the clock generators driving these are modulated by opposite phases of the low frequency modulation oscillator. What this means in practice is that the pitch will be increasing in one channel whilst it is decreasing in the other and vice-versa. It is this technique that is largely responsible for creating a sense of depth and richness in the final result.

The other technique used to widen the perceived stereo effect is to mix a phase inverted version of each channel into the output mixing stage of the opposite channel, and this simple but effective trick is used in many Ghettoblasters to widen the stereo effect when the speakers have inadequate physical separation to produce an effective stereo image.

To complete the noise reduction system, an expander is connected to the output of each delay line (after filtering) to restore the original signal dynamics. There are theoretical arguments against using companders in systems that contain frequency shifting circuitry as this causes mismatching in the encode/decode time constants, but in the case of a chorus device, these effects are negligible and may even contribute subtly to the musicality of the effect.

In Use

I don't know why Roland have been so coy about the specifications of this Boss unit as it is very quiet in use and the brightness of the delayed signal suggests a good bandwidth in this department. Another pleasant surprise, no doubt partially due to the compander system, is that you can overdrive the input to the point where all the LED meter segments are constantly illuminated and there is still no significant distortion.

So much for the quality, but what does the effect sound like? As this stereo system features opposite phases of modulation on each channel, there tends to be none of that drunken pitch wavering effect that you get when a mono chorus is used with too much depth. Instead, the effect is more like that produced by a good multiphase chorus in a string machine, where the effect really does sound like a lot of instruments playing together; not just two instruments - one sober and one drunk.

Used subtly, the unit functions very much like the Roland Dimension D (reviewed HSR June 1984) which gives a feeling of depth and perspective using only a shallow chorus effect - their circuit diagrams indicate that they work in very similar ways.

Less subtle (read blatant) chorus effects are also easily created but all maintain an air of clarity and refinement.

Stereo Enhanced Mono

Commercial stereo simulators utilise a delay line to produce a comb filtering effect whereby the delayed signal is added in-phase to one output channel and out-of-phase to the other. This comb filtering effect is similar to that produced by reflective surfaces within a room containing a point source of sound, and this tricks our ears into interpreting 'space information' or ambience.

By reducing the modulation depth to zero on the CE-300, similar stereo effects can be achieved, and by adding only a very small amount of modulation depth, a mono sound can be given 'width' with no noticeable pitch change or chorus effect. This type of trick is particularly useful in recording when a sound has to be recorded in mono due to track limitations, as the CE-300 can then be used during mixdown to revitalise it.


This unit really comes into its own in a recording environment where its clean, quiet operation can be fully appreciated. As a chorus effect in either mono or stereo, it produces first rate results and has more than enough range to create any reasonable chorus effect, though flanging is not possible as there is no feedback facility. This could be overcome by using the chorus in conjunction with a mixer auxiliary circuit and feeding the chorus outputs) into spare input channels). By increasing the aux send level on the chorus return channel(s), the effect can be made to resemble flanging, but this will be fairly inflexible as there is no way to vary the delay time of the CE-300 and effective flanging really demands a shorter delay time than is required for chorus effects.

As a dedicated chorus machine, the CE-300 is virtually faultless and with a bit of experimentation, it has applications as a stereo simulator and a stereo width enhancer. It may be more expensive than a Taiwanese Hissomatic Megaflanger pedal, but anyone who is serious about his or her recording will appreciate the difference.

The CE-300 Super Chorus retails for £230 inc VAT. Details from any Roland dealer or from Roland (UK) Ltd., (Contact Details).

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


Home & Studio Recording - Mar 1985

Donated & scanned by: Mike Gorman

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Studio FX > Boss > CE300 Super Chorus

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Review by Paul White

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