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Digitech DSP16

Effects Processor

Article from Sound On Sound, August 1991

David Hughes checks out the DSP16, the most affordable of Digitech's new crop of effects units.

Digitech enjoy an enviable reputation in the world of effects processors, and their popularity is well justified. I've been waiting for weeks to listen to their GSP21 guitar processor but, as soon as the local music store takes delivery, it's out of the door before you can say "Barclaycard or Access, sir?"

Digitech describe the DSP16 as a stereo effects processor designed for studio applications and, on paper, the unit's specifications look impressive enough. 16 different reverb and delay effects available in 128 preset programs — there's no user programmability — with stereo processing, and at a very competitive price.

Physically, the DSP16 is as exciting as any standard rack-mounting 1U effects processor is ever going to get. The front panel is dominated by a large rotary dial and a simple 3-digit LED display which shows the current program number and the operating mode. The dial operates in a similar manner to Roland's Alpha-dial in that it can be continuously rotated and has no physical endstops. The main function of the dial is to select the current program from the 128 available, although you can also dial up various other options such as the MIDI and footswitch set-up pages. The dial also features a 'software accelerator' mode so that rotating the dial quickly steps you through the range of programs very quickly, more so than the simple increase in dial speed on its own would produce, whilst slowly rotating the dial increments or decrements the program number by one. This is a clever feature which produced significantly less wristache than other, similar, dials, although without practice it is very easy to overshoot the intended program!

The remainder of the front panel controls consist of, from left to right, the three EQ pots, (bass, middle and treble), followed by the wet and dry signal mix, and the output and input level pots. Finally, there are two LEDs which indicate 'signal detected' and 'signal clipping' conditions. A minor point: the order of the level and mix pots struck me as being slightly unusual, in that I would have expected the pots to read from left to right as input level, wet/dry mix, output level, rather than the somewhat haphazard manner in which they appear. This is a feature which is common across the Digitech range. This may seem trivial, but it's something that's worth considering if you're prone to changing values in a darkened studio at three in the morning.

On the other hand I was pleased to see that Digitech have used a pair of LEDs for indicating 'signal detected' and 'signal clipping' conditions rather than a single multicoloured LED for both functions. Being slightly colour blind, I often find it difficult to detect rapid changes in colour which can occur when a signal is just clipping.

The rear panel sports standard jack sockets for stereo input and stereo output, a bypass footswitch socket, a MIDI In socket for receiving program change messages, and a mains Euro-connector.

The module is something of a lightweight, weighing in at a little over 2kg. It's also not very deep — around 5" — which caused some problems when the unit was bolted into my rack. Most of my rack modules are considerably deeper than the DSP16 — if you need to get access to the rear panel sockets and there are a couple of deeper units either side of the DSP16, then you need the hands of a 5-year old to reach them. (Helpful hint number one: connect all of the leads before you bolt the machine into position.)


The DSP16 is a preset-only machine, and contains 128 programs utilising 16 different reverb and delay effects with variable delay and decay times. So what does it sound like? Pretty damn good. The review unit was very quiet when compared with a number of similar units around the studio — I was really taken aback by its performance in this respect. For the record, Digitech quote the signal-to-noise ratio as being 90dB with a bandwidth of 20Hz to 16kHz — quite respectable, but nothing out of the ordinary.

The only noticeable noise generated by the machine was a ghastly glitch which occurs whenever you switch programs. This is most obvious when a signal is passing through the processor, and the resultant squawk is highly objectionable. Consequently, if you're using the DSP in a live situation, you should be careful to change programs only when there's no signal running through the processor. Sadly, you can't avoid the problem by using the bypass footswitch, because that generates a glitch as well.

The reverb programs are based largely around the more or less standard large, medium and small rooms, hall, gated and reverse reverb types, along with a few 'special' effects. The delays are quite versatile and range from a few milliseconds to a maximum of one second.

The programs are conveniently grouped into three sections: programs 1 - 45 are reverbs; programs 46-105 are delays; and programs 106-127 are combinations of the two. Program 128 is the bypass program. The reverbs are all highly usable, with the large halls being especially convincing. The 'stage/club' reverbs are marvellous, evoking dingy, smoke-filled clubs complete with with small puddles of beer spilled around the floor — well, sort of...

The 'special reverbs' also deserve some mention, simply because they are quite special. Afterglow (program 43) in particular. It just seems to go on for ever — very New Age.


The delay line effects are, like the reverbs, fairly comprehensive, and you should be able to find a delay program that works for almost every situation. If I have any real criticism as far as the audio quality of the device is concerned, it is that the delay programs feel very static, and there isn't much motion in the processed sound. The delay programs divide themselves roughly into two groups: the programs in the first group have delay times from 10ms upwards, rising in increments of 10ms up to a maximum of 100ms. The second group starts at 200ms, and rises in more coarse increments up to a maximum of one second.

All of the programs in these two groups come in pairs, the first having no feedback component, the second with feedback set at either 30 or 40%. I felt that the organisation of these programs could have been better. It might have been more logical to organise the programs as two separate sequences, the first as programs without feedback, the second as programs with feedback, rather than simply alternating the programs.

Programs 86-95 each have a delay time set for a specific tempo, starting at 40bpm and rising to 160bpm, making it very easy to set up syncopated rhythms without the hassle of tweaking a pre-delay pot — just enter the correct tempo into your sequencer.

The multi-tap delays (programs 96-105) are largely excellent, although some will undoubtedly be regarded as little more than special effects. Back And Forth is highly memorable, as it throws the sound from left to right to left in a very unsubtle manner. Galloping 16th's is equally memorable, producing a tight cluster of echoes around the basic sound.

The multi-effects delays are a combination of several of the delay and reverb programs. These are similarly awe-inspiring, combining longish delays of around 250 to 750ms with small, medium and large room simulations. The processed sounds have, depending upon the source you use, a great deal of texture and depth. They also feel less static than the raw delay programs, fattening up even the weakest of sources.


Being a preset-only machine somewhat limits the scope of the DSP16. I would have really liked to see a limited degree of programmability within the machine, even if it went only as far as remembering the positions of the control pots for a specific program. During one particular session I found myself constantly adjusting pots, hunting for the right mix for a given situation. No EQ or level setting will work for all programs, so twiddling becomes a fact of life, something I could well do without.

I was keen to hook the DSP16 into my MIDI sequencer and was disappointed to find that there was no MIDI thru port — this means that unless you've a MIDI Thru box with a spare socket the DSP16 has to be the end link in the MIDI chain — you may find yourself, as I did, running flying leads across the studio.

Setting the MIDI reception channel is fairly straightforward. You rotate the main dial until the letter 'C' appears in the display. You then wait for a decimal point to appear alongside, and dial up the appropriate MIDI channel. Leave the knob in one place for a few seconds, and the instrument reverts to the 'bypass' mode, which is its rather obscure way of telling you that the MIDI reception channel has been set. I have to say that this wasn't at all obvious from the front panel, so don't loose that manual.

Although this is a fairly trivial operation, it is something which you have to go through each time the unit is turned off and on, since there is no battery-backed RAM on-board. This also applies to the program number, which I felt was a real shame because many potential users would prefer to simply leave the machine in a rack to get on with a specific function without ever having to program the instrument again.


I used the DSP in a number of different configurations — mono-in, stereo out; stereo in, mono out; stereo in, stereo out — and I'm pleased to report that at no time did it disappoint. The sound quality was uniformly excellent, and I was very impressed with its performance. It would be easy to place too much emphasis upon the minor faults and shortcomings that the DSP16 might have (lack of Thru socket, no front panel on/off switch), but that would detract from the fact that the unit proved to be a useful addition to my studio, which has been put together with as much attention to quality as cost. Still, accepting minor faults and omissions is a part of studio life which you learn to live with, given a bit of time and patience.

The most important aspect of the DSP16 remains its audio performance, and what it can do to make you sound just that little bit better. I was very impressed with the results on this score, and if I hadn't just blown all my cash on a Roland JD800 then the DSP16 would be given serious consideration.


£278.85 inc VAT.

John Hornby Skewes & Co, (Contact Details).

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Patrick Leonard

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How To Become An Atari ST Power User

Publisher: Sound On Sound - SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.

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Sound On Sound - Aug 1991

Gear in this article:

Studio/Rack FX > Digitech > DSP 16

Gear Tags:

Digital FX

Review by David Hughes

Previous article in this issue:

> Patrick Leonard

Next article in this issue:

> How To Become An Atari ST Po...

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