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Roland SDX330

Dimensional Expander By Dave Lockwood
Published July 1994

Roland SDX330

Everyone is looking for that elusive extra dimension to their mix, and Roland's latest unit claims to deliver it right out of the box. Dave Lockwood assesses dimensional expansion for himself.

The SDX330 Dimensional Expander is the latest addition to Roland's RSS‑based Dimensional series, joining the SRV330 Reverb (reviewed SOS August) and the SDE330 (SOS October 1993). RSS (Roland Sound Space) is a processing system which utilises psychoacoustic properties to create the illusion of sounds originating in a three‑dimensional space, rather than just being placed across the traditional frontal soundstage. There are, of course, a number of well known simple techniques for making the stereo image wider than the loudspeaker placement would seem to allow. These usually employ a little of the opposite channel's signal being fed anti‑phase into the other side. But RSS goes well beyond this and, in a well set up demonstration, really can cause signals to appear to be originating from behind the listener's head!

In the previous 'Dimensional' series units, the RSS‑based 'three‑dimensional' element consisted only of 'Azimuth' (static left/right placement) and 'Elevation' (nominal vertical 'positioning', over a range of 60 degrees up or down) parameters for the early reflection element of the effect. The SDX330, however, incorporates dynamic 360 degree panning effects in the horizontal plane, with control over speed, direction, and start position.

Easy Editing

The SDX330 is housed in the customary Roland 1U matt black rack chassis, with familiar two‑line backlit LCD window, plus program number display. The LCD shows the program name at all times, in Play mode, but the user is given the option to have programs recalled with a specific parameter also visible. In Edit mode, the LCD shows up to three parameter and value combinations simultaneously. As there will invariably be more than three parameters making up a preset, the visible ones can be horizontally scrolled, using the alpha dial or +/‑ keys. The three function keys can then be used to select one of the visible parameters for editing — once this is done, the alpha dial and +/‑ keys will now act on the value. There are about as many different operating systems in this world as there are multi‑effects units, and each has its strong and weak points. Roland's is about as simple and obvious as they come, and certainly one of the fastest to learn.

Both inputs and outputs utilise unbalanced jacks, with the signal path configured with a genuine stereo in, stereo out format, with truly independent processing of each channel. Separate +4dBu, ‑20dBV switching for inputs and outputs gives a high degree of interface flexibility (there is sufficient range and headroom on the input and output stages to make usage with a ‑10dBV mixer no problem). Bypass and Control footswitch jacks are also provided, in addition to an Expression pedal input for real‑time parameter control. MIDI In, Out and Thru sockets, and an acceptable length of captive mains lead (laudably complete with moulded‑on UK plug) complete the rear panel connection facilities. The MIDI Input allows real‑time MIDI control of effect parameters, as well as external patch selection and program data loading. The real‑time MIDI control setup can be unique to each patch, and is easy to programme yourself.

High quality, 16‑bit, delta‑sigma converters and a 44.1kHz sampling rate give the SDX330 a subjectively clean sound. Roland's practice of legending their level bargraphs with nominal zero well below the actual digital clip point undoubtedly encourages safe drive levels. Significantly under‑driving the input produces no more degradation than you would expect, but should certainly be avoided in any situation where the whole signal is passing through the unit. Internally generated noise, hiss, hum etc, and noise induced in surrounding equipment by the externally radiated field, are all at acceptable levels. Electronically, the SDX330 is an impeccably behaved processor.

The unit incorporates a generous 300 program memory locations, with numbers 1‑200 available for user storage. Presets are accessed serially via the alpha dial or +/‑ keys (with the usual increased scroll rate when holding one switch whilst pressing the other). A MIDI program map can be memorised if you need access to presets beyond the normal 127 limit via MIDI program number. Program selection, either from the front panel or via MIDI, is fast with no audible glitching in the output. Real‑time MIDI control also seems to be generally free of audible vices.

The SDX330 offers 16 effect algorithms, with a parametric equaliser and real‑time MIDI control assignments common to all. Entering Edit mode, one of the three Function buttons can be used to select which of the immediately visible parameters is to be edited. Once selected, the parameter name will flash, confirming that its value can then be edited via the data entry knob or the +/‑ keys. The Page key allows access to the other parameters via sideways scrolling. Interestingly, whichever function (Func 1, 2 or 3) is selected (flashing) when you press Page, will still be selected when you press Page again to return to Edit mode, although it will now be a different parameter. Once you know this, you can make use of it to avoid an unnecessary keystroke — you just stop scrolling when the parameter you want is under the 'selected' position. Another nice touch is that if you press the Function key for an already selected parameter the display changes to a more detailed version of the parameter name, plus an indication of the units (dB, Hz etc) in which the parameter is specified. This is extremely handy when you are still getting to know some of the more cryptic truncated names.

Memory management is particularly straightforward; edited programs may be compared with the original before being stored, and edits can be freely copied and written to any of the 200 user‑locations, provided the memory protection is off.

You have a choice of six different types of modulation waveform, plus the ability to set the relative phase and polarity of the LFOs. Inter‑channel cross‑mixing, independent LFO speeds, and panning add further spatial complexity...


Many of the SDX330 parameters will be instantly familiar. The majority of the effects are still based on the conventional 'modulated short delay‑time' process; however, there is considerably more sophistication than normal. You have a choice of six different types of modulation waveform, plus the ability to set the relative phase and polarity of the LFOs. Inter‑channel cross‑mixing, independent LFO speeds, and panning add further spatial complexity, but one of the parameters that excited me most was the 'crossover' facility. This allows the input signal to be divided into a maximum of four bands, each of which is then able to have its own separate Chorus parameters. It is a common problem when applying any type of modulation or 'thickening' effect that the rate and depth settings which sound best at high frequencies (HF) will create too obvious a 'churning' effect at the bottom‑end; set things up so that the bottom‑end is subtle, and the HF range will have lost most of its 'ring' and sparkle. The SDX330 multi‑band approach lets you optimise the effect for each range — and it works a treat.

A basic Pitch Shifter (plus or minus 100 cents) is also incorporated, allowing static pitch change thickening, plus an Ambience parameter, which seems to be an early reflection set, giving the sound a very real localisation. Another major highlight of this unit for me, however, is its rotary speaker (Leslie) simulation — this has been attempted by many competing units, but without ever quite capturing the richness and spatial complexity of the real thing. Roland's emulation is about the closest I have heard, particularly in the vital slowing‑down phase.

Some excellent vocal doubling effects can be achieved with the SDX330's more subtle programs, and all the classic 'clean Strat' jangle effects are there, in varying degrees of intensity and spaciousness. The SDX330 really will let you create the full range of processes in this area, from the richest, heaviest thickener you have ever heard, to barely perceptible artificial imaging and spatial enhancement.


The Roland SDX330 is an excellent sounding processor, irrespective of whether the three‑dimensional RSS‑based element is of interest to you. The price will inevitably be regarded as a little on the high side for what many may regard as just a 'dedicated chorus unit', but the SDX330 is so much more than that. It might seem contradictory, in the context of a unit that is intended, amongst other things, for 'thickening' treatments, to use the word transparent, but the description is definitely appropriate here. To anyone only used to the band‑limited, slightly distorted modulation processing typical of cheaper multi‑effects units, the clean, high bandwidth, 'airy' sound of the SDX330 in these applications will be a revelation. This is a superb sounding unit, with some unique features, and has to therefore be considered reasonably good value for money. It may not be for everyone, but those people who need effects of this type will be hard pushed to find them better implemented elsewhere.

Dimensional Monitoring

Whether you can actually perceive any out‑of‑speaker effect with Roland's Dimensional Series units depends very much on your monitoring environment. The room must be sufficiently dead (especially at mid to high frequencies), and particular attention must be paid to avoid HF reflection from the surfaces immediately behind the listener, before you can expect to hear the full effect. If you are looking for the kind of dramatic step‑up in spaciousness that you obtain when going from a simple mono chorus to a stereo chorus, you will be disappointed. The SDX330 is considerably more subtle than that. I don't, however, want to underplay my enthusiasm for this unit, for it offers many of the best sounding chorus and doubling effects I have ever heard. Personally, I don't care if the 3D element amounts merely to a heightened sense of depth and perspective — in many ways that, to me, seems far more useful than anything dramatically out‑of‑the‑speakers.

SDX330 Algorithms

The 100 factory programs are derived from 16 algorithms, with Parametric EQ and MIDI real‑time control assignments common to all.

  • STEREO CHORUS: a true stereo input and output chorus, with variable phase between left and right channels.
  • STEREO 3D CHORUS: true stereo chorus, with 3D positioning added.
  • 3D PANNER: Dynamic 3D panning effects, with control of speed, direction, and start point.
  • SPACE CHORUS: a wide, spatial chorus, very accurately replicating Roland's own SDD320 Dimension D unit.
  • 2‑BAND CHORUS: true stereo chorus with two‑way band‑splitting for separate chorusing of different frequency zones. Crossover point variable from 400Hz‑4kHz.
  • 3‑BAND CHORUS: true stereo chorus, with three‑way split. Crossover points, 100Hz‑1kHz, 800Hz‑8kHz.
  • 4‑BAND CHORUS: mono input, stereo output chorus, with four‑way frequency division. Crossover points, 100Hz‑1kHz, 400Hz‑4kHz, 800Hz‑8kHz.
  • STEREO 8‑PHASE CHORUS: a complex true stereo chorus, with independent parameters for each of the eight 'voices', including LFO phase and polarity.
  • 16‑PHASE CHORUS: a mono (in and out) chorus, with preset Modes, rather than independent voice parameter control.
  • DETUNE CHORUS: a true stereo, non‑cyclic chorus effect, with six high resolution pitch shifters in parallel.
  • ENSEMBLE: stereo/mono chorus using LFOs of differing speeds. Uses Preset modes, rather than user‑variable parameters.
  • WAVE CHORUS: true stereo chorus, with choice of six LFO waveforms.
  • VINTAGE CHORUS: Roland CE2‑type analogue chorus simulation.
  • STEREO FLANGER: true stereo flanger, with choice of LFO waveform.
  • ROTARY: uncannily accurate simulation of rotary cabinet, complete with overdrive stage, and offset speed‑up and slow‑down rates for top and bottom rotors. Great!
  • AMBIENCE CHORUS: chorus with simulated stereo ambience, adding greater spaciousness to the effect.

Example SDX330 Parameters

The Rotary Speaker algorithm

  • Speed: Slow/Fast
  • Horn (fast): 5.00 to 10.00Hz
  • Rotor (fast): 5.00 to 10.00Hz
  • Horn (slow): 0.05 to 5Hz
  • Rotor (slow): 0.05 to 5Hz
  • Rise Time (horn): 1 to 100
  • Rise Time (rotor): 1 to 100
  • Fall Time (horn): 1 to 100
  • Fall Time (rotor): 1 to 100
  • Mix Balance: 90:10 to 10:90
  • Mic Setting Mode: Off‑mic/On‑mic
  • Horn Depth: 0 to 100
  • Rotor Depth: 0 to 100
  • Horn Tremolo: 0 to 100
  • Rotor Tremolo: 0 to 100
  • Overdrive: On/Off
  • Overdrive Gain: 0 to 100
  • Overdrive Drive: 0 to 100
  • Overdrive Level: 0 to 100
  • Diffusion: 0 to 100
  • Effect Level: 0 to 100m
  • Plus 3‑band parametric EQ and up to five real‑time control assignments.

Real‑Time MIDI Control

The SDX330 can transmit and receive data on any of the 16 MIDI channels or operate in Omni mode (send and receive channels may be independently set). MIDI Program Change messages are recognised, and the unit can both send and receive System Exclusive. A MIDI activity LED in the display window confirms that MIDI information is being received. Reception of MIDI Program Changes can be switched off, if necessary. MIDI expression pedal messages can be assigned to a controller or filtered out altogether — a 'soft Thru' option allows all incoming MIDI data to be merged with any data generated from the SDX330.

Within each preset, up to five effects parameters may be assigned to real‑time control, with the control sources including both MIDI, and the rear panel switch and pedal inputs. Sources of control data can be mapped to any of the parameters within the algorithm on which the patch is based. Multiple assignments to the same parameter are allowed, but — as always — it is important to avoid discontinuities in the data whilst audio is present in order to avoid audible glitching.

Maximum and minimum parameter value limits may be defined for real‑time control assignments — the usual trick of swapping the upper and lower values in order to reverse the control direction is also possible. The SDX330 real‑time control assignments are easy to programme, and vice‑free in operation.

SDX330 Specifications

  • Converters: 16‑bit, delta‑sigma, 44.1kHz
  • Frequency Response (effect): 20Hz to 20kHz (Dry):5Hz to 70kHz
  • THD (effect): 0.02% or less at 1kHz
  • Dynamic Range: 90dB or better
  • Audio Connections: Unbalanced 1/4" Jack
  • Input Range: ‑20/+4dBm
  • Input Impedance (‑20dB setting): 300kOhms (+4dB setting): 10kOhms
  • Output Range: ‑20/+4dBm
  • User Memories: 1 to 200
  • Preset Memories: 201 to 300


  • Some superb sounding effects.
  • Simple user interface.
  • Good external control facilities.


  • Limited range of effects.
  • 3D 'RSS' element may disappoint some users.
  • Could be seen as expensive.


A particularly fine sounding unit, with efficient and easy editing. Offers a professional standard of audio performance at a semi‑pro price.


Roland SDX330 £699 inc VAT.