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Roland SDE-3000 Digital Delay

The very latest microprocessor controlled delay, offering flange and vibrato among its many features.


The microprocessor revolution of the last ten years seems to have had implications nobody foresaw in the mid-70's when the 4-bit and then the first 8-bit CPUs were produced. Initially these devices were scorned by 'serious' computer users who, in general, considered the microprocessor a quaint and rather amusing toy and failed to recognise it as the threat it was to become.


Even the designers themselves had modest aims. Their original intention was merely to introduce an intelligent logic chip which could be used in vending machines and the like! They never envisaged that anybody would have sufficient programming ingenuity to make the things run as computers in their own right and they certainly didn't imagine that anybody would write operating systems, high-level languages, advanced applications software such as word processors, and so on.

Yet all this happened, and in a remarkably short space of time. Nowadays the micro finds its way into hundreds of different consumer goods - some very sophisticated, some less so. Many ideas which would have been impossible or uneconomic to realise a few years ago are now being brought to fruition, and one of the more accessible results of this technology is that it has enabled digital audio to establish itself. The digital delay line is now considered almost a standard fitting in even the smallest of studios and is portable enough and cheap enough to be used by many musicians on stage. It offers more versatile delay-times and bandwidths to its analogue competitors and, of course, prices are continually falling and may be expected to do so for some time.

The microprocessor is taken for granted as a standard component of a modern signal processor and its recent humble beginnings are already being forgotten. The Roland SDE 3000 is a typical example of a microprocessor-controlled effects unit and retails for £799. It is a digital delay line offering long delays and wide bandwidths at a very high quality indeed, and conforms to the standard 19" rack mounting system, measuring 1U in height. The unit is finished in black with colour-coded lettering in white, yellow, green and blue which is helpful and not nearly as gaudy as it might sound. A twelve-digit LED display is employed to show the state of the system. The overall result is a unit which is beautifully smart and rather futuristic.

Layout



The majority of the controls are situated on the front-panel and all the connections (made by ¼" jack sockets) are at the rear. In an effort to offer better resolution in setting up, Roland have abolished the more usual rotary pots almost entirely and replaced them by a simple and yet effective switching system, a move which seems to be much favoured by manufacturers at the moment.

The switching works as follows. The delay time in milliseconds, feedback level, delayed signal level, modulation rate, and modulation depth are all shown simultaneously on the main display. Each setting may be incremented or decremented using a pair of momentary action buttons which will auto-repeat if held down. This allows the delay to be specified to an accuracy of 0.1ms for delays of less than 10ms and to the nearest 1ms on higher delays, and allows the other control settings to be made to an accuracy of 1 in 100. This is much better resolution than could be achieved using a pot but sacrifices speed of setting up at times.

Working from left to right, the front-panel houses a bypass push-button with a corresponding LED, a VU meter (-20dB to +6dB which employs six LEDs, the input pre-amp level control which may be set to give any gain from -22dB to +6dB (using the only pot on the front panel), filter on/off (which is cryptically described in the manual as helping to provide a realistic echo effect). Delay x2, delay phase inversion, modulation on/off, feedback phase inversion, and the memory controls discussed below follow, and next come three LEDs showing the modulation rate, the delay rate (eg this flashes every 2 seconds if a 2000ms delay is set), and Delay on/off, the main display which is very bright and clear, the switch pairs used to alter the control settings, and finally the mains power switch.

The memory itself is very easy to operate. Eight separate channels are provided and so up to eight individual effects may be programmed in advance and called up at the touch of one or two buttons. The memory is divided up into two banks (A and B) of four channels. One push-button alternates between the two banks and four further buttons are used to select the desired channel. Each of the switches has an LED built-in which changes colour from green to red according to which bank is selected. Hence it's surprisingly easy to keep track of the system and these five switches allow any channel to be called up quickly. There is a very brief pause after a new channel has been selected while the unit changes its settings but this is unlikely to cause any problems unless the effect needs to be changed during a fast piece.

Each memory channel remembers the settings of delay time, feedback fraction, output level of the delayed signal, modulation rate and depth, and also stores the state of the filter, delay phase, modulation, and feedback phase. In fact the only parameter that is not held in memory is the gain of the pre-amp. To program an effect into memory the required settings are made manually and then the desired channel push button is held down for about two seconds, until its LED starts to flash. Once this has been done the previous channel contents are erased and the new settings are substituted. The memory retains its contents even when the power is removed so the unit does not need to be reprogrammed each time it is used.

The rear panel houses a potentiometer which allows the delay time to be increased by up to 50% at the expense of bandwidth. Then come modulation CV output to allow two units to be synchronised together to process a stereo signal, and CV input, to allow triggering by another SDE 3000, an external LFO or the optional footpedal.

Four further jacks permit very comprehensive remote switching to be performed in a number of ways. A footswitch may be connected to 'delay' to simply bypass the unit as required. Pressing the 'hold' foot-switch causes the contents of the memory to recirculate indefinitely resulting in continuous sequencer-like patterns. The 'preset' jack steps successively between the eight memory channels. So if a number of effects are programmed into memory in the order in which they will be used on stage, they can be called up very easily.

Feedback loop send and return jacks are also provided. Roland suggest two possible uses for these connections: first, a graphic equaliser may be placed in the feedback loop to add variety to the system, colouring echoes for instance. More imaginatively, two 3000s may be interconnected by patching the send of one to the receive of the other to give delays of up to 9 seconds!

Input, delayed output, and mixed output are available, and finally a level-matching switch (-20dBm or +4dBm) is provided which may be used in conjunction with the input gain pot to cater for a wide variety of input devices. An electric guitar, keyboard or mic may be directly connected using the -20dBm setting.

Construction



In addition to looking good the unit is also very well-built. The case is strong and sturdy and surprisingly heavy for its size. It is certainly rigid enough to be used freestanding on stage if kept well out of the way of feet and similar hazards, although a rack is obviously preferable.

The case is reasonably easy to open although a self-adhesive sponge pad supporting the top cover has a tendency to tear and wouldn't last very long if the unit were regularly disassembled. Roland make a plea in the manual (under the heading of 'Important Notes') that the unit should never be taken apart and to be honest there's no real reason (other than plain curiosity) why anyone should want to dismantle it.


Once the top and bottom panels have been removed the electronics can be seen in detail - the case is rather full. A large densely-packed single-sided PCB holds the main circuitry, with the power supply mounted separately on a smaller board. A third board mounted just behind the front panel to house the displays and the switches is just visible. The transformer is sensibly mounted inside a metal case to shield the audio sections from its strong magnetic field.

The main board houses a small piggyback board holding the memory chips. The whole circuit contains over 50 integrated circuits, none of which are mounted in sockets. This seems a strange omission considering the price of the unit and could make life interesting if anything ever needed replacement. The circuit features a common mixture of analogue, TTL, and CMOS.

Two resistors are mounted on the back of the main board as an afterthought. This is obviously a last-minute design modification which does not merit the vast expense of redesigning the whole board. Overall the construction is of an extremely high standard, showing care in every stage of production which should result in a reliable instrument.

Results



The figures quoted in the manual state that the system offers a dynamic range of over 100dB at very low levels of distortion. The claimed bandwidth is 10Hz to 17kHz on the main delay range falling to 10Hz to 8kHz on the delay x2 range. For stage use even the smaller bandwidth is perfectly acceptable. The signal-to-noise-ratio for the delayed signal is quoted as a startling 88dB. In use the system seems to live up to these figures. As always, signal levels are vitally important but if these are chosen carefully the unit runs very well indeed.

Eight sample control settings are provided. These include:

Echo


Various versions of echo may be obtained varying from sharp slapback effects through to delays of several seconds. The examples given in the manual illustrate the effect of varying the feedback (which determines the number of repeats produced) and the delay level (which controls the strength of the repeats). A little modulation may be added to give a fuller sound but the modulation depth must be kept low to avoid unpleasant effects. The feedback fraction may be set greater than unity and when this happens the echoes gradually become louder instead of dying away.

The unit must be praised since the echoes it gives are virtually indistinguishable in quality from the input fed into it. The results are always very clean and bright. If the feedback level is advanced to approach unity the echoes may be made to continue for very long periods and only after quite a number of repeats does the degradation in signal quality become unacceptable. This degradation occurs because the signal is digitised and then returned to its analogue form each time it goes around the feedback loop, and the minor distortion which results from each of these processes gradually accumulates. The filter may be employed to reduce the degradation considerably. Such a use of the unit would be uncommon since the 'hold' facility can be used instead to give infinite repeats without degradation.

One of my favourite effects with a DDL is to select a delay of something like 90ms with lots of feedback to simulate the ambience of a large room. The unit behaved admirably, giving an effect akin to reverberation on soft passages with sharp distinct echoes on staccato passages.

A sound-on-sound example is given in the manual which is merely a long echo (3 seconds in the manual) which repeats just once. Any input signal is replayed faithfully by the system after a delay.

Doubling and Chorus


The results for doubling are very similar to those for echo since the two effects have a lot in common. The sounds produced are natural and very accurate although perhaps not quite as thick and rich as I had expected. Two examples are given, both using delays of about 25ms. The first is wonderfully rich and believable and really brings an instrument to life. The second was less pleasing but still gave a thickening of the sound.

Flanging


This is one of the better flangers that I have heard recently. A wide range of phasing and flanging effects may be obtained. The character of the delay depends very strongly upon the length of the delay chosen and Roland have obviously considered this since they arrange that delays below 10ms are set to an accuracy of 0.1ms. This makes the SDE-3000 far more versatile as a flanger than the majority of its competitors. Heavy feedback can be added to increase the depth of the notches giving a very useful set of effects. The phase inversion switch further changes the tone of the sound.

Vibrato


A delay of about 25ms may be used in conjunction with the modulation section to give true frequency modulation. With the modulation depth set at zero the signal passes unchanged. If the depth is increased slightly the change is dramatic and the sound quality improves tremendously. Vibrato is a useful all-purpose effect since it can be used subtly to improve a sound without causing any strong or noticeable colouration. It is one of the easier effects to create technically and most DDLs are capable of producing good results: the Roland is no exception and performed to its usual high standard.

Conclusions



I must confess that I've come to like the Roland very much. It is well designed and well made and generates some excellent effects. The price may seem a little high at first sight but the unit really is worth every penny. When compared with other quality systems the Roland actually begins to appear cheap. For those with a more limited budget the SDE 2000 reviewed in E&MM, May 1983 is £600 and the SDE 1000 (see this month's Home Studio Recording) is £400. The units are very similar in performance, the essential difference being their maximum delay times.

The controls are well laid-out and very easy to use, but the one criticism I would make is that it takes a long time to alter the settings. For instance, to change the delay time from its minimum value to its maximum value takes just over 3 minutes. On stage this would be a ridiculously long time which, I suspect, is why so many memory channels are provided. In the unlikely event that more than 8 totally different effects are required the system might be troublesome. However, I am inclined to think that this would be fairly rare. The remote switching facilities are very flexible and would make the unit very easy to operate on stage.

The manual is written in pidgin English at times but is usually clear and concise and does contain more or less everything you might need to know. The system is actually very easy to use and set up and programming is extremely simple.

The 3000 is a good indication of the way things are going in the design of DDLs, with wide bandwidths and accurate noise-free digital encoding. It gives very good performance at a relatively low cost and has a lot to offer the guitarist, keyboard-player, or general-purpose musician and recording enthusiast.



 
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Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.

 

Electronics & Music Maker - Mar 1984

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Studio FX > Roland > SDE-3000 Digital Delay

Review by Ed Stenson

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