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Ibanez GE3101 Graphic Equaliser



The Ibanez GE3101 is a 1/3 octave graphic equaliser with thirty-one ISO frequency bandwidths ranging from 20Hz to 20kHz. A single input jack means that the unit can accept inputs from a wide variety of sources, such as synths, high impedance microphones, tapedecks or preamps. The EQ offers 12dB of cut or boost at any of the selected bandwidths, as well as for the overall output level. Therefore a single frequency can be boosted effectively by 24dB. The gain of the EQ can also be switched from 12dB to 6dB to allow greater control and accuracy.

Construction



The unit is sturdily constructed with a two piece metallic outer shell around a steel framework. The knobs on the 32 sliders are securely glued to the shaft so hopefully they should all still be there after the first period of usage (which is more than can be said for the ones which are just pushed on). The action of the sliders is very positive and free from any slippage, small indentations at 0dB facilitate swift return to neutral EQ state. A peak level LED illuminates at +15dB leaving 9dB headroom before the output overloads.

Three push buttons on the front panel switch EQ in or out, change EQ gain from 12dB to 6dB and turn on the High Pass filter. The EQ In/out switch is mercifully quiet (an important consideration for practical use) and an LED illuminates above each of these switches when in use. The Low Pass Filter cuts 18dB/octave below 40Hz, eliminating stage rumble, microphone handling noise and various other power wasting sub-sonics.

By simply removing four screws the back of the outer casing can be taken off revealing the component side of two circuit boards and the transformer. These are very firmly attached to the steel framework and wires crossing over the onboard components are kept to a minimum. The other half of the outer shell can be removed offering access to both sides of the PCBs while leaving everything intact. Even at this stage the slider pots are completely protected from dust etc. yet by removing more screws connecting a third PCB to the front panel, the pots can be fully accessed if they should ever need cleaning. The main circuit board contains the thirty one bandpass filters, made up by sixteen 4558 op amp mini-dips, sixty five mica capacitors, resistors and thirty one trim pots (which needless to say, should not be tampered with). The smaller board contains input, amp and output components another five 4558s and twenty one transistors. The layout of the PCBs is very neat and precise and all soldering and finishing is to a very high standard.

The use of the trim pots as part of this inductorless resonator circuit allows finely tuned, accurate frequency responses and minimal filter overlap. On the review instrument the centre frequencies measured up to the +/-0.5dB response very well, when checked with oscilloscope and spectrum analyser, apart from 8kHz which was a bit high.

Signal to noise ratio specified at less than -95dBm and THD better than .02% give the 3101 specifications generally associated with a much higher price tag. The unit is designed to be rack mounted and at just 44mm high it only takes up one unit of space in a standard EIA 19" rack.

Usage



The main use of EQ in a studio tends to be in making up for the shortcomings of other equipment, either electrical or instrumental. Microphones and speakers can both be susceptible to picking up externally created noise (cable inductance etc.) also their own characteristics can often cause problems. Matching a speakers rolloff with bass boost reduces system hum and knowing the whereabouts of presence peaks in your microphone response allows you to cancel out howl before it occurs.

In live performance, the acoustic properties of the hall can cause many problems. Boomy vocals, whether or not they reach feedback level, can often be due to a particularly nasty standing wave creeping round to the front of the microphone, and even sibilance can sound terrible in some venues and non-existent in others. PA problems like these have caused premature baldness for many sound engineers and a good EQ unit can be worth its weight in gold, making your second-hand 5½ string orange box sound like the latest Scratchibacki Stradbucker in overdrive and turning open string scales into Mozart's 43rd symphony (well almost).

Vocals



The frequency range of vocals, whether male or female, falls roughly between 70Hz and 12kHz, with the majority of characteristics lying between 200Hz to 1kHz. Gutteral sounds and 'pops' occur from around 80Hz to 150Hz and sibilance from 10kHz upwards. Therefore these problems can be greatly reduced by cutting the relevant level of the offending frequency. If boosted around 3-5kHz a very clear pure voice is produced. This area can be very penetrating and boosting too much around these frequencies can easily become over-powering. Sparkle and intensity can be added around 8-12kHz and 200-600Hz gives body and fullness to the sound.

Guitar



Cutting the response of an electric 6 string around 40-100Hz creates a muddy jamming sound, particularly if boosted around 8kHz as well. Boosting 3kHz-5kHz enhances many instruments in the same way as it does the voice. Acoustic guitar for example can be given sparkle and brilliance by boosting 5kHz and above. 8-10kHz emphasises light gauge 12 strings and the all important glide from chord to chord of Flamenco technique.

Electric basses can often be an absolute pain to get right without an equaliser, drowning everything in sight with low harmonics before any cutting power (normally feedback) is achieved. By reducing the boomy 40-100 Hz register and boosting low to middle (400-630HZ) articulate and 'growly' bass is produced.

Drums



You too can have boomy tom toms, with a good bassy sound by boosting in the 80-200Hz region and cutting back at around 315Hz. Crisp, clear side drums are particularly apparent at 2kHz and above. A good thuddy bass drum sound can be achieved by cutting back at 630Hz and boosting the bass range at 100-160Hz, you can even switch out the High Pass filter, boost down to 20Hz and feel the vibrations loosen the nails in your shoes.

Piano



The piano is a notoriously difficult instrument to record, particularly if your microphones are not quite up to scratch. This is where EQ can help. By boosting around 100Hz and cutting 5kHz some bass can be restored to the honky tonk upright which is a requisite of every £5/hour recording shed that most first recordings tend to be made in.

All these suggestions are fine until you start recording voice, two guitars, drums, piano and bass, then things start to get a little more complicated, room acoustics come into account and compromises have to be made. In general, bass instruments, on initial recording, can be forfeited somewhat for treble sounds for various reasons. Treble can often be lost between you and the listener, particularly with noise reduction, and if bass needs to be turned up it can be done so by tone controls, easier than treble boost which creates more noise (tone controls on most domestic hifi simply start to boost from 1kHz - the most effective range as far as the ear's concerned). So cutting back at selected bass frequencies in favour of higher ones to obtain a balance, can often give the best end product.

This type of 'Don Quixote' EQ 'seeing life as it should be, not as it is' makes the Graphic Equaliser indispensable in a studio, well worth the saving in time and wasted tape alone.

Creative EQ



Another side of EQ is the creative use of the equipment. Often faults seem to appear from nowhere when putting together a piece with a multitrack recorder. Sounds which are great on their own suddenly loose everything when a second or third part is added. This is normally because of the cancellation due to two sounds of similar harmonic content being superimposed. This can be helped by boosting or cutting while the second signal is being rehearsed, correcting with EQ before the second track is laid down.

By boosting 10-18kHz and cutting 2-7kHz of a vocal line, a distinct edge is produced, while manipulation of the 2-10kHz frequencies produces timbre changes which can make interesting filtering effects.

As a cure for feedback the graphic is well suited. Feedback occurs when overall gain between microphone to speaker exceeds unity. Peaks of this nature can be due to a variety of factors eg. uneven frequency responses in the system (normally in microphones or speakers) or acoustic properties of the room producing standing waves in front of the axis of the microphone. As the gain increases feedback occurs at the peaks. By using EQ these peaks can be smoothed out, allowing the overall gain to be increased. Wherever possible EQ should be added at the recording stage instead of being used entirely as a post-recording treatment as this helps keep S/N down to the minimum.

Conclusions



Specification

Frequency response: 20-20,000Hz
Hum and noise: -95dbm
Gain (switchable): +/-12dB or +/-6dB
Maximum input level: +/-20dBm
Low Pass Filter: 40Hz; 18dB/octave
Total Harmonic Distortion: less than 0.02%
Dimensions (WxHxD): 482mm x 44mm x 233mm
Weight: 3.1kg

The importance of EQ is quite obvious and the GE3101 is a very effective machine. Ibanez have purposefully built the unit keeping rack space to a minimum. I personally think that a graphic equaliser is something which can afford to take up a little more space as accuracy and accessibility throughout the entire cut and boost range is very important (the 3101 only allowed about 1" of movement for 24dB of change). Adding size to the equipment would also allow a greater physical indentation at the 0dB mark, which would also be an improvement in my opinion. The Low Pass filter cutoff could be set a little higher or ideally be made variable from 20-80Hz as this would filter out any possible rumble. As it stands however, I consider the GE3101 to be a worthy addition to any space and expense conscious studio.

RRP (inc VAT) £291.50.

Distribution is via Summerfields, (Contact Details).



Previous Article in this issue

Yamaha R1000 Digital Reverb

Next article in this issue

Soundproofing Windows


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

 

Home & Studio Recording - Jan 1984

Donated & scanned by: Mike Gorman

Gear in this article:

Studio FX > Ibanez > GE3101 Graphic Equaliser


Gear Tags:

EQ
Graphic EQ

Review by Glenn L. Hughes

Previous article in this issue:

> Yamaha R1000 Digital Reverb

Next article in this issue:

> Soundproofing Windows


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