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JHS Digitec Delay

"A fully digital signal processing device at an affordable price" is the description given to this digital delay from John Hornby Skewes, and for once the words ring 100% true. At a VAT Inclusive selling price of £275, the JHS Digitec represents unbelievable value for money, and this diminution in cost should also have practical benefits in terms of recording quality, as more and more home recordists replace their battered, old tape echo devices with the likes of the Digitec.

In terms of features, the unit offers the usual array of controls housed in the ever-familiar 1U high, 19" rack-mounting case. The unit is capable of a maximum delay of 1024 milliseconds with a quoted delay bandwidth of 16kHz. This theoretically will produce no discernible difference between the original and delayed signals. This was generally the case, I found, but with signals exhibiting a lot of high frequency content, such as a high pitched polysynth chord, discrepancies were evident. However, it is usually the case that in a mix, the delayed signal will be set at a lower level than the original, untreated signal, which would overcome this problem.


All controls are front panel mounted and allow you to produce a full complement of delay related effects, from straightforward echo and automatic double tracking to a clean, bright reverb. The provision of a triangle wave low frequency oscillator permits the chosen delay time to be automatically altered or 'modulated', producing the usual flanging, phasing and chorus effects associated with digital delays.

Some people argue that digitally-produced flanging and chorus, does not have the same warmth as that produced by analogue means eg. bucket brigade devices. This is generally true, and is often due to the lack of background noise in digital devices. The Digitec delay in question certainly produced a 'bright' flanging effect, but the added depth and ability to select the 'phase' of the delayed signal in relation to the original, resulted in a much warmer effect when Delay was set in its antiphase position.

Delay Selection

Selection of the desired Delay time is achieved by the combined action of the Time and Factor knobs. Time is switchable between its five positions which set the delay to 2, 8, 32, 128 or 512 milliseconds. You then utilise the Factor control to tune the delay to a finer setting. Clockwise gives a maximum doubling of delay time set by the Time control, whilst an anticlockwise movement halves the preset time at its extreme setting. In this way, any delay time is possible from 1ms to 1024ms.

Unfortunately, the Digitec unit has no onboard display of delay time, which partly accounts for its lower price, so you must use your ears to fine tune the delay to your required time. Personally, I don't think the lack of a display makes any difference if the unit is to be used purely for musical applications. Actually, I would suspect that most users of a digital delay will adopt a similar approach to the selection of delay times, even on devices with a display - it's only natural that you'll need to fiddle around a bit with the knobs until you hear what you want.

With a delay time selected, the balance between the original and echo levels can be set using the Direct and Delay output controls. Direct is a straightforward volume control but Delay works in an unconventional manner. In its centre detented position, no delayed output is heard, whilst increasing the level anticlockwise or clockwise selects the out-of-phase or in-phase signals.

The choice of 'phase' is only really of concern when modulation effects are produced, as it enhances the richness and depth of the treatment. The combined direct/delay output signals are then available from the front or rear panel Mix sockets, whilst the delay only signal is sent to the rear panel Delay socket.

If multiple repeat echo is required, a long delay time should be chosen and the Feedback control advanced from its central 'off' position. As with the Delay knob, the Feedback control can also select in or out-of-phase signals, providing even greater control of the possible tonal variations of effects. At extreme settings (and especially with short delay times) feedback caused the unit to break into oscillation, with a resultant surge in output level. Set just on the brink of oscillation though, the Feedback knob proved invaluable for producing a very 'hollow' flange with delay around 20ms and modulation depth near full.

In addition to the phase change facility, the Feedback section contains a 10kHz hi-cut filter on/off selector switch. This filter essentially removes the treble from the delayed signal and has a cumulative effect with Feedback selected. In other words, the delayed signal is filtered once, then re-circulated to the input several times, dependent upon the amount of feedback chosen. Each time it re-circulates it is filtered again.

The major application of this filter circuit is in the creation of reverberation effects. Digital delays with a single delaying mechanism, are incapable of producing realistic reverberation. The nearest they come to a reverb effect is the production of 'flutter echo' or 'hard reverb'. To simulate the natural dropping off of high frequency sound, which is a characteristic of natural reverberation, simple digital delays employ a low pass filter to cut out the treble content. The end result remains unconvincing, but still useful as a treatment for your recorded sounds. The Digitec, as suspected, is no different in this respect from any other single tap digital delay on the market.

The modulation section, already described, offers Rate and Depth controls which can be used in several ways. For normal mod effects like flanging, the Rate control governs the speed of the LFO sweep, ranging from one sweep every ten seconds for slow 'yawning' flanging, to ten sweeps per second (10Hz). This upper limit, in practice, is sufficient to produce Leslie speaker effects, heavy vibrato and quasi-pitch shifts (if a long delay time has been selected), with the amount of effect being determined by the Depth control. With this knob set to zero no modulation is evident.


The final feature offered by the Digitec is the 'freeze' or infinite Hold. This allows a signal up to 1024ms in duration to be stored in the memory and repeated infinitely with no degradation in sound quality. This function is only operative when the Time control is set at 512ms, so it is possible to freeze your sound then switch to another delay time and set up a further effect, keeping the signal still frozen in the unit. You then switch back to the 512ms setting, and the signal will still be cycling around. Whether this is of any use or not is really down to an individual's needs!

The Hold mode can be selected either by pressing the front panel pushbutton after playing the sound you wish to store, or by means of an optional footswitch plugged into the rear panel Hold jack socket. A similar option is available for the Bypass mode, which simply cuts out the delay circuitry completely, giving the direct signal feed at the outputs. Both pushbuttons have red LEDs above them to indicate on/off status.

The obvious use of the Hold facility is in creating short repeating phrases or rhythms, as a basis for songs. Laurie Anderson used this sound to great effect on her 'O, Superman' single some time ago. As a special effect in a live situation or during a mixdown, you can freeze a sound into the unit, then punch it in using the Bypass button whenever you require. You can also change the pitch of any frozen sound by altering the Factor control.


Input and output jack sockets are provided on the front and rear panels. The -50dB and -20dB inputs are for mic and line/instrument signals respectively, and levels are set by the Level control and Headroom LED display which incorporates a green 'power on' indicator. The -20dB outputs are suitable for feeding into most insert jacks on a mixer, for patching into an auxiliary send/return circuit or for direct connection to a guitar/keyboard amplifier.


I was very impressed by the Digitec unit. It offers a full selection of effects, that are easily created, at a very good price. The 16kHz bandwidth quotation is a bit suspect but the device does produce good quality treatments. With a maximum delay time of just over one second you are limited in what you can achieve via the Hold function. A longer delay time would be better for this effect, but in normal delay mode anything greater than 1 to 1.5 seconds is redundant, as the applications for a longer delay are surely musically limited.

Construction and layout are both good, and the colour-coded sections are a useful way of differentiating functions. To sum up, the Digitec represents very good value for money and should be of great value to any home recording installation.

The Digitec sells for £275 inc VAT.

If you have difficulty locating one in your local music shop try contacting the distributors; John Hornby Skewes, (Contact Details).

Also featuring gear in this article

JHS Digitec Delay
(12T May 84)

Browse category: Studio FX > JHS

Previous Article in this issue

Splicing for Effects

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Test Tones

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


Home & Studio Recording - Apr 1984

Donated & scanned by: Mike Gorman

Gear in this article:

Studio FX > JHS > S1024 Digitec Delay

Gear Tags:


Review by Ian Gilby

Previous article in this issue:

> Splicing for Effects

Next article in this issue:

> Test Tones

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