This digital delay rack-mounting unit from Korg came as something of a surprise — not that echo units are unfamiliar products for a synthesiser manufacturer, but that this instrument's high quality and variety of features should attract a large number of studio musicians who don't normally go to Korg for processing machines.

The SDD-3000 has an exceedingly high bandwidth of 17kHz for maximum delay time of 1.023 seconds. All the usual effects like flanging, doubling, chorus, vibrato, Doppler effect, slapback and echo can be obtained at the push of a button from 9 user-programmable memories, with full editing available.

Modulation is extended to three waveforms, including an unusual 'random' effect, and envelope follow, as well as external control. Footswitch control of several functions makes the SDD-3000 very flexible as a rack mounted processor on stage. Input and output options make it easy to match up to both semi-pro and most professional recording studio situations (provided unbalanced signals are acceptable).

Layout

The general layout and construction is very good indeed, with tidy interlinking wiring and well spaced-out component boards, due to the large depth. The unit measures 381(D) x 46(H) x 482(W)mm and weighs 6kg.

The front panel is in dark blue with yellow/white legending showing each section of the instrument clearly. Pushbuttons have a 'precise feel' action, some with built-in miniature red LEDs to show 'effect on'. A front power switch has been used without introducing hum and optional front in/out jack sockets usefully override rear connections.

Panel Controls

Input section. Front and rear panel standard jack inputs can be tailored for maximum input without distortion by a 3-way attenuator switch for -30, -10 and +4dB. A level control makes the final adjustments in conjunction with the 'Headroom' LED meter calibrated in 5dB steps from -20 to 0dB (green LEDs), with a peak red LED for +3dB signals.

Regeneration section. Apart from the standard echo Feedback control, an Invert button gives an out-of-phase Feedback signal, effective for changing pitch of flange and chorus effects. There are also two filter switches for low frequency cut-off (Flat, 125, 250 and 500Hz) and high frequency cut-off (Flat, 8k, 4k and 2kHz) of the delayed signal only.

A Hold button is another good feature on the unit, providing infinite repeat of a fixed 1.023 seconds prior to selection. Delay time and feedback are held at maximum but filter, invert and modulation controls can be changed to create 'sound-sampling' of very high quality. During 'Hold', further signals at the input are sent straight through, allowing you to play over the top of a musical segment — the optional footswitch (Korg PS-1 or any single pole type switch) can be connected to the rear 'Hold' socket (without disconnecting front panel Hold) and is an effective control in performance. Exciting sounds are created by briefly using Hold at the start of a single chord bar and continuing to play with it.

Modulation section. Time domain variations are created successfully by good modulation controls and Korg have given us plenty to choose from. Two standard waveforms, triangle and square, plus a Random wave output are switch-selected. Frequency is variable from 0.1 to 15Hz (with LED indication) and intensity can be over a range of 2.1 (a change from 100% to 50% of the displayed delay time). Triangle will produce vibrato style modulation, Square gives trills up to a very good span of an octave, Random is the kind of S/H effect used on oscillators, although its action is smoothed as it's intended to be used for more realistic doubling as well as special effects. In practice, the intensity has to be kept low to avoid sudden pitch leaps, but with a 'voice vibrato' (around 8Hz) frequency rate, it does produce a gentle variation of pitch against the original signal that is quite natural. For dramatic effects it's a lot of fun to use.

More sensible, is the provision of an Envelope Follower which causes the delay time to vary with the input amplitude envelope. As volume increases, the delay time becomes shorter. Most pro-units have this feature and it is a desirable modulation at any part of the delay range, for responding to the input — longer delays appear as a sound gradually fading or chorus effects become more animated from a voice input and so on.

Delay time can also be modulated externally and both the Korg MS-01 and MS-04 are useful for this (0 to +5V range). Unfortunately, all internal modulation is disabled when a summing situation would have been much better. However, the MS-04 will create some very responsive performance pitchbend and glissando quite unlike your usual instrument pitch change effects.

Effect and Output sections. The final parts in the signal chain define the balance between the direct and the delayed signal using the Effect control. The Output section gives several types of mono and pseudo-stereo signals. A front panel standard jack output can be switch-attenuated (-20, -10, +4dB), while the three rear outputs are all +4dB to match most studio and PA equipment. All outputs are unbalanced and can drive 600 ohms to full rated level (+21dBm max). An invert button will change the phase of the front and also the rear panel +MIX/MONO outputs (in-phase mix of direct and delayed signals). A Bypass switch will turn off delayed effect completely and is footswitch operated if you prefer. Two other outputs are provided for Direct signal and for out-of-phase-MIX of direct and delayed signals (set by Level Balance).

The stereo imaging can therefore be set for optimum effect using a mixer with 2 outputs from the SDD-3000 set to full left and right pan settings, and usually with level balance set for more of the delayed signal. Using +MIX/MONO and -MIX outputs in this way gives the best live sound, but it is unsuitable for most recording due to phase cancellation of the signal. For best recording results you use Direct and —MIX/MONO outputs.

Programmer

Nine separate effects programs can be stored, recalled and edited at any time. All controls on the front panel (apart from In/Out settings) are remembered — making programming very versatile. A 5-digit numeric display (red for Program number and yellow for delay time in mS) is used to indicate the current Program number, 1-9 for stored programs, and 0 for manual setting of controls. Write and Program buttons store or select programs easily. Programs can be edited (once any control is changed during recall of a stored program, a decimal point appears by the Program No.) and copied into a new location using UP and DOWN buttons. These buttons also set the Delay Time from 0 to 1023mS. Counting speed is conveniently increased the longer a button is held.

Korg's dual footswitch (PS-1) is handy for Program selection one step at a time using rear UP and DOWN sockets.

High Quality

Obviously a lot of development time has been put into making this instrument very worthy of itself. Priced at £1025 (including VAT) it is a high quality processing tool that has a very clean signal output — most of the time it's hard to distinguish direct and delayed in terms of signal degradation and the filter section is used for specific effects only. The modulation range is wide enough for achieving good pitch changes in the time domain and Korg have stuck to a modest (by today's standards) second or so of delay to keep a very wide bandwidth, with low distortion (0.03% quoted), and 94dB effect dynamic range without noticeable 'breathing' effects through the use of 13-bit converters. Incidentally, the user manual is very useful as it describes fully the processing treatments available.

Further details from: Rose Morris/Korg, (Contact Details).