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Peavey DeltaFex

Digital Stereo Effects Processor By David Mellor
Published January 1997

The Deltafex offers a stripped‑down price to match its streamlined facilities. David Mellor checks it out..

Peavey's Deltafex is unashamedly an entry‑level, non‑MIDI multi‑effects unit, which sets out to combine low cost (its retail price is just £155) with simplicity of operation. Its main function is to provide reverberation, though it also caters for basic delay and modulated delay effects such as chorus, phasing, flanging and rotary speaker. The format is the familiar 1U rack, and the equally familiar external power supply also puts in an appearance.

The most obvious feature of this unit is its operational simplicity, though, unlike earlier 'preset only' devices, the Deltafex allows you to change up to two key parameters per effect in real time. There's no liquid crystal display, and no buttons other than the power switch, and while this simplicity might seem limiting, at least you know you're going to be able to use the Deltafex to its full capacity straight out of the box.


The Deltafex has two inputs and two outputs which work in the conventional manner, where the input signals pass straight through under the control of the wet/dry mix knob and retain their stereo image. In addition, the two signals are summed and sent to the effects processor, which creates pseudo‑stereo effects. The stereo inputs only need to be used when you're putting the unit directly after a stereo source, such as a stereo keyboard; when you're working with a mixing console, you need only use one post‑fade aux send. If you only connect the left input, it will automatically be linked to the right channel.

The only other connector, apart from the power connector, is a footswitch jack which, in conjunction with an optional footswitch, may be used to mute the reverb input, or change speed in the case of the rotary speaker effect. This is especially useful on stage.

On the front panel are six knobs and a printed table of effects. Although in the studio you would control the input to the unit from the mixing console, leaving the dry/effect mix control set to 100% effect, there are situations (such as when using the unit in‑line with a stereo keyboard), where you might want to control these parameters from the Deltafex itself. Accordingly, input level, output level and wet/dry controls are amongst those provided.

It is vitally important to be able to set the correct input level on a reverb unit, in order to steer an optimum course between overload distortion and circuit noise, and to do this, you need effective metering. I can understand that a bargraph meter might be too expensive an addition for a unit in the Deltafex price bracket, but surely a three‑colour LED would have been a cost‑effective option? What's actually provided is a two‑colour LED that remains unlit when the signal is low in level, shows green when the level is acceptable, and lights up red when the signal is within 6dB of clipping. I prefer the system where green indicates signal present, yellow indicates a healthy signal level, and red shows impending clipping.


The effects are called up using the Preset Select control, which is similar to the rotary switch found on a number of Alesis reverb products. As is usually the case with this type of switch, you can't always be sure which setting you've selected, especially if you're not looking square on to the control. Considering that you have to set this control to an accuracy of 22.5 degrees to get the preset you want, a larger knob would have been justified, even though the white legend is clear enough.

The Deltafex has 16 presets, comprising plain reverbs (with one gated reverb), one reverse reverb, and a selection of other effects. Two knobs (labelled Parameter 1 and Parameter 2) then provide instant access to two parameters for each effect, though the parameter being changed depends on the preset you've called up. In the case of the reverbs, for example, you can control reverberation time and HF (high‑frequency) damping. Reverberation time is simply the time it takes for the reverb to die away (by 60dB, in theory), and damping would normally control the high‑frequency reverberation time. In a real room or auditorium, low‑frequency reverberation is very difficult to control, while high frequencies are easily absorbed by carpets, soft furnishings and wall coverings. This means that most real rooms have a longer reverberation time at low frequencies than at high frequencies, and it is this characteristic that the Deltafex seeks to give you control over. The front‑panel table of effects not only names the presets but also indicates which two parameters are controlled by the Parameter 1 and Parameter 2 knobs.

Since the five basic reverb presets are arguably the most important (and probably would be the most often used) effects produced by the Deltafex, I'll look at them in a little detail:

  • Preset 1: Chamber Reverb. This sounds like a smallish concert hall, possibly the size of a school hall, with hard walls, at least two of them parallel (the reason I say this is that I can hear a bit of a flutter echo — not much, but it's there), and with a moderate amount of architectural detail and HF absorption, as might occur in real life from introducing movable drapes. Although the reverb time is variable between 150ms and five seconds, the decay time is also affected by changing the amount of damping. There's always a certain amount of high‑frequency reflection evident, even at the shortest reverberation time, while the damping parameter seems to control the hardness of the surface, from marble to candy floss.
  • Preset 2: Plate Reverb. A plate reverb should generate a rapid build‑up in reflection density, with a bright, characteristic tonality. This preset is quite dense at high frequencies, with distinct reflections from the edges of the plate, and is particularly good, at shorter reverberation times, for adding a little 'air' around an instrument or voice without the reverb being noticeable.
  • Preset 3: Room Reverb. This doesn't sound a million miles away from Preset 2, except that the balance of frequencies is shifted upwards. I think I might have called it a small plate.
  • Preset 4: Cathedral Reverb. This preset offers ultra‑long decays, up to eight seconds, that are ideal to complement your selection of Gregorian Chant samples.
  • Preset 5: Spring Reverb, doesn't quite reproduce the twang of a spring to the extent that it occurs in real life — and it doesn't 'sproing' when you kick it! At certain settings, Preset 5 seems to sound identical to Preset 3, and to be honest, there's an underlying similarity between most of the presets.

The two parameter controls are where the Deltafex scores, however, since if you find that the overall sound of a preset is to your liking, you can fine‑tune it to your desired reverb time and high‑frequency damping very easily. It's much easier to do this with knobs than on a parameter‑access, programmable unit. However, I found that the review unit took a second or two to settle down after changing parameter settings, which could lead to some unusual effects during the settling period. This was particularly noticeable on the gated reverb preset.

Even if you're stacked up to the ceiling with reverbs, the Deltafex is still worth buying as a dedicated delay box.

Any of the Deltafex's basic reverb programs are good for vocals, even the cathedral reverb, since you can adjust the parameter controls to get a short, dense reverb that enhances the voice rather than obscuring it, as is sometimes the case with other reverb units. The DeltaFex also sounds good on drums, though you can feel that you're hearing an artificial sound — it's not as realistic an imitation of a real drum room as some other (usually more expensive) units achieve.

I'll just mention the other presets briefly, starting with Preset 6, Gated Reverb, which is, as you would expect, great where you want a lot of density close to the original sound, without a long reverb tail to clutter up your mix. Reverse Reverb (Preset 7) is really a bunch of reflections with a slow build‑up followed by an abrupt shut off, and works fine as a special effect. The delay presets (8‑11) are unexpected gems. Delay isn't used as much as it used to be, probably because it's tricky to set up on most digital effects units, and there are usually other, more seductive presets just a button‑push away. The Deltafex offers Bright, Warm and Dark delay presets, where the delay time and number of repeats is set with the two parameter knobs. The difference between the presets is in the rate of roll‑off of high frequencies.

As well as simple one‑off effects, there's a nod in the direction of multi‑effects in the Reverb+Delay preset, and also a nice ping‑pong Stereo Delay. The remaining effects are Chorus, Phaser, Flange and Rotary Speaker, all of which are designed to sound best when used without mixing in the original signal. Although they are all perfectly usable, the best for me is the Phaser preset, which reminds me of the old analogue effects pedals of the '70s.


In conclusion, the very accessibility of the Deltafex would make it a good first reverb and effects unit, particularly as it encourages you to create your own sounds rather than simply skip through manufacturers' presets. As a second reverb in a more sophisticated setup, it would easily justify its place in the rack, though I'd say that its greatest strength is, perhaps surprisingly, its delay presets, since there are so few delay units available that you can adjust with knobs. Even if you're stacked up to the ceiling with reverbs, the Deltafex is still worth buying as a dedicated delay box. At the price, you could hardly go wrong.


  • Knob interface.
  • Two parameter adjust controls.
  • Good basic reverb quality.
  • Excellent delays.


  • Yet another anonymous external power supply to get mixed up with the rest.


An excellent first or supplementary reverb unit, with a valuable selection of other effects.