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Roland E660

Digital Parametric Equaliser

Article from Music Technology, October 1988

The advantages of programmability and the power of MIDI spread further into the studio environment. Vic Lennard checks out Roland's programmable parametric equaliser.

As both professional and domestic audio standards rise, the quality of outboard equipment must keep pace. Enter Roland's state of the art parametric equaliser.

TO MY MIND, the equalisation on mixing desks has always been of a dubious nature. Standards have certainly improved since the days of simple "shelf" controls for treble and bass, but when it gets to the point where even SSL have to redesign their EQ circuits, then we can be sure that not everything is quite right - yet.

Most desks now have parametric equalisation for mid or perhaps high and low mid frequency bands, some even with variable resonance. But increases in noise level are all too often the price to be paid for their availability. Alternatively, as part of a MIDI-controlled mixdown, MIDI patch changes can be used to control particular frequency ranges for equalisation. But this system suffers from glitching as memory changes take place. And what's the point of being able to master recordings in the digital domain if sound quality is limited by analogue equalisation?

Given all these problems,- and the fact that if there's a gap in the market someone will fill it - it was only a matter of time before the necessary black box appeared - in this case, the Roland E660 Digital Parametric Equaliser.

Description and Specification

THE E660 IS a four-band serial/parallel or eight-band serial parametric equaliser housed in a standard 2U-high rack-mountable black case. The front panel is split into three parts - parameter rotary controls along with input level and channel-band selector on the left, a 96x32 pixel backlit LCD and level/channel indicators in the centre, and two keypads on the right. One, which I'll call keypad 1, has eight buttons, and the second (keypad 2) has 16. Many of these have dual operations assigned to them. The rear panel has stereo audio input and output sockets (balanced through XLRs, and unbalanced through standard jacks) set to the professional level of +4dBm, three MIDI sockets, and digital in/out by means of either two phono sockets or by Roland's proprietary optical interface. An LCD contrast control (which should be on the front for ease of use) and a removable mains lead complete the guided tour of the rear panel.

The spec is impressive: a signal to noise ratio of better than -80dB, a frequency response of 20Hz-20kHz within 3dB and a dynamic range of greater than 94dB (which converts to at least 15.6 equivalent bits of resolution). The A/D converter is of the 16-bit linear variety, while Roland claim D/A conversion of 18 bits by use of companding and a 28-bit parallel arithmetic digital processor. The result is a machine that's extremely quiet, accurate and certainly up to CD quality.


POWER UP PROMPTS the message "Roland E660 Digital Paramedic Equaliser". I expect pidgin Japanese in the manual - in fact I would actually miss not having a laugh on occasions - but on the screen?

As there is no overall output control - a feature that I would personally have liked to see - the input has to be set up quite carefully to allow for any overall level increase. Pressing the Utility button on keypad I brings up the Input Pad page, allowing individual setting of digital and analogue signals by ensuring that the red +8dB indicator doesn't light up. In fact, holding the signal level down to +1 or +3 allows more headroom for equalising. Parameters are changed by positioning the cursor over them from keypad 1 and then entering new values from keypad 2. A nice touch is that the Enter button has to be pressed to instate the new value, allowing the setting of a parameter to be executed accurately at a specific time.

The analogue input can also be altered by rotating the dual ganged pot on the front panel, but this works independently from the previous page which should permit the user to mix a digital input with an analogue one, as the connection of one doesn't disconnect the other - an interesting idea.

There are three modes of use, which can be switched between by using the shift and mode buttons on keypad 2 followed by +/- to scroll through the menu. Using the channel selector rotary control along with the EQ button on pad 1 allows access to all parametric settings, no matter which mode the E660 is being operated in. In eight-band mode the frequency bands occur in pairs corresponding to the Low, Mid Low, Mid High and High bands of four-band operation. Centre frequencies are variable as follows: 30-960Hz, 200Hz-6.4kHz, 500Hz-16kHz and 800Hz-20kHz. Each may be cut or boosted by 12dB and the resonance varied between 0.3 and 9.9.

In any mode, the highest and lowest frequency bands may be set for shelving or peaking by pushing the resonance (Q) rotary control, which acts as a spring-loaded switch. The resonance used on this machine is a constant gain version, meaning that any change will have its level determined by the setting of the Level control. Altering values is easy - simply turn any of the parametric rotary controls and the present values for that band are shown on the screen. I detected a small amount of audio noise when turning the level control at any speed, and I also noticed that the result was not quite instantaneous - probably due to the fact that the control is operating a microprocessor. However, the knobs do have a high degree of resolution, level being given to one decimal place, Q to two decimal places and frequency to about 1.3% rounded to the nearest whole number. Unfortunately, values can not be incremented/decremented by the +/- buttons. In four-band mode, channels can be set independently, or the settings on one channel an automatically be copied to the other. In the latter case, especially useful when setting up in stereo, two settings can be arranged and listened to by switching over the channel selector.

All changes are imposed on memory location 0 - called the Temporary Area - and then have to be saved to one of the 99 user memory locations. Each of these locations, which can be named with up to eight characters, consist of all EQ data along with delay values and Thru on/off. After writing information to a memory, the existing contents of that location are automatically transferred to memory 0 as back-up.

Other features

ONE FEATURE WHICH stands out is the Graph mode, usable in four- or eight-band serial modes and accessed by pressing the relevant key on pad 1. With all level controls set to zero, a straight line appears across the screen - the graphic display is independent of input. Tweak the knobs, press the graph button and Sam's your uncle! Nine to ten seconds later (or about 20 seconds in eight-band mode) the display appears, showing how the settings have affected it. It's a pain that it takes so long, but it really is useful - and you an move a control while the graph is on the screen and see the redraw in 2-3 seconds, which is great for fine tone shaping.

Next there are two pages accessed by Utility (keypad 1) which control pre-delay (of up to 500 milliseconds) for an input in any mode, and post-delay for each frequency band in four-band parallel mode only. My initial reaction was that these features are here because they are easy to implement on this piece of equipment and look nice on the spec sheet. However, it's true to say that time delays are useful in terms of large PAs, where columns of speakers are separated by large distances. I also discovered an interesting application while experimenting: use three bands for equalisation and pick out the frequency at which the hi-hat is dominant on the fourth one, using a high Q value. Now post-delay the three EQ bands by about 20 milliseconds, which leaves the hi-hat effectively ahead of the rest of the track - and driving it like an inter-city 125.

The E660 also features a hum canceller which can operate at a central frequency of between 30Hz and 90Hz, with a fine adjustment of one decimal place, and a ratio intended to eliminate hum to various degrees by acting on the central frequency and its even-numbered harmonics.

Don't get too excited by the prospect of taking all your old recordings and removing the earth loop buzz - it isn't that simple. From what I an ascertain, Roland have used a special type of comb filter called a Recursive Filter, which, depending on the parameters used, will act in a number of different ways. The one in this case uses a degree of feedback, which is fine if there are no transients but behaves badly when there are. Much of my testing was carried out in the digital domain using a Sony DTC1000ES DAT recorder, and it was apparent that the hum canceller acts more like a digital delay on the bass drum, with variable feedback dependent on the ratio setting used. In other words, if any of the musical programme exists near the central frequency or the adjacent even harmonics, they will be adversely affected by the canceller.

Finally, one hefty gripe - an audio Thru which takes half a second to settle is of limited use. Of course, it can be used for simply checking the EQ setting against the input, but that's all.

Digital Ins and Outs

A SONY/PHILLIPS digital interface has been used on the E660. This is of the unbalanced variety operating at about 0.5 volts peak-to-peak, and utilising an integral clock synchronising signal in the code (as opposed to the professional standard of three BNC connectors for left, right and clock). The only problem this can give rise to is that it's awkward to clock a domestic R-DAT machine to the E660. To be fair to Roland, anyone intending to use this feature would probably be using a professional machine and a converter.

In the wonderful, digital world of CD and DAT, a "block" is made up of 192 frames, and each frame of information is made up of 32 bits. For the technophiles, there are four bits for a header and 20 bits for audio, although only 16 are used at present, four are reserved for future advances in audio, and four are termed V (Validity), U (User), C (Channel Status) and P (Parity). The channel status bits within a block are of interest here because they contain data concerning the sampling rate, copy prohibition and emphasis on/off, allowing the E660 to automatically set itself up for each of these criteria when receiving a digital input. Emphasis is a gain curve giving 0dB at 3.1kHz rising at 10dB at 10kHz and above. Recognisable rates are either 44.1kHz (the professional standard) or 48kHz (the domestic DAT standard adopted to hinder CD pirating).

MIDI Implementation

PRESSING THE UTILITY button gains you access to the E660's three MIDI pages. The first of these allows a channel to be set for reception or transmission, as well as having the option of Omni on. The second allows a MIDI Program Change table to be set up by assigning the relevant memory location to a program change number, 128 patches being available.

The third MIDI page permits two MIDI dumps - total memory and the Program Change table. The former takes about 10 seconds to transfer and is a one-way dump - it's actually intended for transferring data to another E660. Bearing in mind the point about patch changing memories on a mixdown and the attributable noise, especially if the new memory has a different mode setting, such a program change is risky at best. So, what can be done with SysEx?

Unfortunately, the E660 does not respond to any data requests, even when a configuration is set up on Hybrid Arts' Genpatch. This device will ignore dump requests whether they are bulk or a specific parameter dumps. This is a pity, because it would be possible to extract a particular setting and to replace it at the relevant moment without actually changing the memory location, and so cause no noise to be created.

There is a way to get around this to a certain extent. The MIDI implementation in the back of the manual is excellent (I think this is the first positive thing I've ever said about a manual) and you can set up a string of bytes to alter practically anything in the temporary area (memory location 0). Consequently, a frequency band could be altered and its level reset to zero when the next frequency band is changed, allowing one band at a time to be set. Transmission takes less than 10 milliseconds when working in this manner - the change is instantaneous and noiseless. C-Lab's Creator/Notator and new versions of Hybrid Arts' MIDITrack will make good use of this as they both permit the writing and sending of SysEx messages within a sequence.


OBJECTIVELY, THE E660 is straightforward to assess as it has a professional spec and excellent features - a quality item. The only direct competition is the Yamaha DEQ7, which interfaces digitally with their DMP mixer series but requires the FMC1 format converter to write to and read from R-DAT. The recommended retail price of these two items is the same as that of the E660 - £1288 - but as the DEQ7 is not a conventional parametric equaliser, but a graphic/parametric hybrid with filters borrowed from the TX16W sampler, a direct comparison is difficult.

Subjectively, I love it. Having mastered a track from B16 onto R-DAT via the digital interface on the E660, I used it to cut and boost sections under sequencer control while monitoring on the graphic screen. I can assure anyone it has its uses in a studio - and not just a professional one. This machine is highly usable in a semi-pro setting and at a justifiable price - bear in mind the improvement in a final mix and the attitude of A&R men towards good demos. If you're thinking of (or already have) invested in a DAT recorder for mastering purposes, you have to realise that digital equipment of this standard is important if you're going to benefit from the extra dynamic range.

OK, the E660 has a couple of dodos - the hum canceller to name one - but overall, well done Roland. One last thing: don't go rushing down to your local music shop to test it out, as only the 10 Roland System houses in the UK will actually be allowed to stock it.

Price £1288 including VAT

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Previous Article in this issue

Art of Glass

Publisher: Music Technology - Music Maker Publications (UK), Future Publishing.

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Music Technology - Oct 1988

Gear in this article:

Studio/Rack FX > Roland > E660

Gear Tags:

Digital FX
Parametric EQ

Review by Vic Lennard

Previous article in this issue:

> Art of Glass

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