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Echo Unit Supplement

DeltaLab Effectron ADM 64



Three new studio quality digital effects from DeltaLab Research Inc. have recently been introduced as the 'Effectron' range. The review instrument was the ADM 64, which is the lowest price unit at around £337 (plus VAT) and offers a flange ratio that is claimed to be twice that of any other digital unit available. Although we haven't fully checked that out, the ADM 64 does provide a full three octaves of flanging (8:1 flange ratio) which is in excess of anything else we've reviewed to date.

The other two Effectrons, the ADM 256 and ADM 1024, are single channel multi-effects processors for flanging, doubling, chorusing, echo and infinite repeat. All the units notably have a full audio bandwidth of 16K and wide 85-90dB dynamic range at all delay settings.

The Effectrons are all housed in the same smart 'shades of blue' 19" rack case measuring 1¾" high and 7" deep. Construction is of the usual high standard from this respected company who have become well known through products like their DL-2A Acousti-computer and DL-4 Time Line.

The PSU has a toroidal transformer to reduce hum and the digital memory consists of 16K dynamic RAM, with CMOS digital ICs, bipolar/MOS analogue devices and an all-steel chassis all contributing to the quality. The same basic PCB board is used for each of the three Effectrons.

DeltaLab use their own patented Adaptive Delta Modulation for digital encoding. Pre-emphasis is applied to the input prior to this A to D conversion, which converts the audio signal by analysing both the value and the slew rate of the signal.

Rear panel connections are standard jack sockets. There's one for external voltage control modulation of the internal VCO. All kinds of interesting effects can be created using this input with a synth or voltage pedal. A 2-octave sweep requires a range of 0 to +5 volts while the full 3-octaves needs -.62 to +6.2 volts. Most synths will handle the former range and the Korg MS-04 pedal is particularly exciting to use, making sweeping 'real glissandos' as well as S/H effects that are stunning on percussion.

Also included is a by-pass socket which is in fact a switch with stereo tip-to-ring contact for direct signal, plus input and output sockets.

Flanger/ Doubler



The ADM 64 provides effects based round two delay ranges, selected by a central push switch on the front panel for Flange or Double. Six rotary controls allow wide variations to be made in both modes, especially with the provision of an envelope follower in addition to the more usual periodic modulation.

Controls

Although there are only a few controls, they all need careful selection during processing to get the most out of the unit.

The input signal can be between 100mV and 2V and a green 'Active' LED remains on if a suitable level signal is present, while a red 'Limit' LED indicates 0dB onset of clipping and/or slew limiting. Plenty of headroom is available in practice.

Once the delay range is selected by the Flange/Double switch, a delay control adjusts times from minimum to maximum at centre and then to envelope follower mode in clockwise half of the control. Flange range is 1-4mS and Double range is 16-64ms. In the envelope follower mode, the delay automatically follows the amplitude envelope of the input signal.

Feedback control is unusual in that it provides negative as well as positive feedback from 0 to almost 100%.

The Modulator section is an LFO that modulates the internal clock from one cycle every 10 seconds to 10Hz using the Speed control. The size of the flange or doubling delay sweep is set by the Width control, with maximum clockwise position giving the full 3-octave sweep. Other settings allow the Delay control to set the sweep 'centre' delay time and there is useful interaction with this and any external control CV in all but the minimum positions of Delay and Width, so some 'playing' with the controls is necessary to get the desired result.

Output level is dependent on the input signal level and simply has a Delay Mix control for adjusting direct output (at centre) with amounts of in or out-of-phase processed signal.

Effects



1. Straight Delay

Three main types of effect can be produced. First, 'doubling' which delays a voice or instrument by 16 to 64mS. When this delayed signal is mixed with the original it produces a more 'full-bodied' sound. The Envelope Follower can add transient detuning for more natural effects on vocals.

The straight delay can also be used for sending to a separate reverb device to give a feel of early reflections (known as pre-reverb delay). A third effect is called Haas-Effect Image Shifting which can be used to stabilize images in a stereo field, since the ear does not relocate an echo in a different spatial position from the original sound if the delay is less than 40mS.

2. Short Delay Feedback

Comb Filtering lets you dramatically alter the overtone structure and tonal quality of any steady sound.

Flanging is a result of modulating the short delay with or without feedback that makes the comb filter effect. The familiar 'metallic' sweeping and shifting of harmonics is heard from different notes.

Using in or out-of-phase feedback will give different colouration to the signal, and with maximum feedback, a tuned resonance or ringing of 'peaky' sounds at a definite pitch will result (that's different with feedback polarity changed). It's particularly good with percussion.

3. Time base modulation

Manual pitch shifting is easily done by turning the Delay knob. Automatic control is done with the Modulator to give smooth sweeps of pitch similar to vibrato. The Envelope Follower also modulates the clock for effective pitch 'time domain' changes from percussive envelopes like piano, guitar and drums.

Studio quality



This is an extremely efficient Flanger/Doubler unit that should find its way into many budget studios for creating specific effects.

On minimum delay setting the treated signal was very clean, but with some slight 'edge' ringing on a raw synth square wave input at maximum delay, which is hardly likely to affect most music inputs. The LFO modulator set at minimum still has a slight effect unless Delay is set to minimum. The review machine's LFO had a rather sharp triangular wave that was fine except for the full 3-octave sweep. Anything above the lowest Speed settings produced an unpleasant 'squelch'. At reduced sweeps below maximum there was no problem.

Above all, the ADM's clarity from the wide bandwidth, plus the wide modulation range makes it very acceptable for its reasonable cost.

The Effectron range is distributed in the UK by Scenic Sounds Equipment Limited, (Contact Details).



Previous Article in this issue

Cutec CD-424

Next article in this issue

Roland SDE-2000


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

 

Electronics & Music Maker - May 1983

Echo Unit Supplement

Gear in this article:

Studio FX > DeltaLab > ADM 64


Gear Tags:

Digital FX
Delay

Review

Previous article in this issue:

> Cutec CD-424

Next article in this issue:

> Roland SDE-2000


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