Electrix Filter Factory


The filter factory (which according to the electrix website is part of their 'old' range, and no longer available) is one of those instruments which does 'exactly what it says on the tin'. Electrix have taken the classic format of distortion adding preamp followed by a low pass filter and put a twist on it, to create a simply gorgeous unit. Analogue filters and waveshaping distortion, digitally controlled from the front panel and also under midi control. The sound of this unit is now an essential part of the Exponent production process.

The filter factory itself is in a 2U rackmountable case, with large easy to grab knobs, and bright leds to indicate the status of the filter, distortion circuits and LFO. The front of the case is nicely shaped, and is very distinctive and attractive, although some may not find it to their tastes. The base of the unit is angled so that if so desired it may be used as a tabletop unit, in which case the front panel controls are pointed slightly upwards. A small touch, but one that will be appreciated by many I am sure. A nice green background colour finishes the front.

Round the back we have stereo input and output sockets, (on jacks for line level, and handily also on phonos for record decks. These phono inputs include RIAA correction and a ground point, and is an easy way to get a recording straight from record deck to your computer.)

Midi in / out / thru are also provided along with CV inputs for the filter cutoff (integration with modular synths is described in the manual, however, not having the necessary hardware to test it, I could not check how efficiently this part of the unit works). Finally we also have an IEC input for the power, a midi channel selection switch (of which more later) and the power switch.<

All of the controls on the filter factory feel substantial, and as if they would last a long time. (the words 'tank' and 'built like' spring to mind.) However, for my liking they are a touch too smooth, and I for one would like a little more resistance to their movement. The buttons are again responsive, and it is VERY easy to tell with a glance exactly how the unit is set up, because of the plethora of lights on this unit. (although it can become annoying having so many lights blinking at you.)

The filter factory is split roughly in to three parts. To the left of the unit is the Buzz circuit. This has to be the best part of the filter factory and definetely makes it stand out from other filters. It is simple enough in its premise. There are two knobs, buzz and trim. Turn up the buzz to distort your signal to taste, this is basically overdriving the input level to the preamp. Then adjust the output level (trim) so that you get the minimum clipping, or add more distortion to taste. And it sounds fantastic. Almost any sound can go through this and instantly sound improved. The buzz circuit appears to work in the same way as a valve distortion unit (see the tubehead preamp review), with the amount of distortion increasing logarithmically as the level increases (as opposed to a fuzz box which simply clips at a fixed level.) Not subtle (I can't see it being used to clean up a sound!) but perfect for adding analogue grunt. Exponent advise balancing the levels of the buzz and trim knobs so that they are are roughly equal distances away from centre in opposite directions. Then add a bit of each to fatten up the sound. The subtle range of different sounds that can be achieved by doing this are yet another reason why this is such a killer piece of gear.

The filter follows this section. You can select from highpass, bandpass, lowpass and notch, (all two pole stereo) or you can apply a four pole mono filter instead. Cutoff and resonance are continuously variable across the audio band, and the resonance will self oscillate at high settings (allowing you to play it from midi or the CV inputs as an oscillator, although it sounds quite screechy with some settings)

Included in this section is the built in LFO. This is syncable to midi clock and is also divisible in seven different values. (ie - you can have the LFO running at of the BPM that it is set to). Tempos can be tapped in via the Tap tempo button and there is also an envelope follower so that you can make the filter follow the dynamics of your playing. The big flashing tap tempo button makes it easy to beat match to odd tempos and to visually check the BPM. Speed is also variable with an independent speed knob, although changing this will cause you to lose sync with Midi clock, (pressing the tap tempo button once will cause it to resync to midi clock) and it would be nice to have a lock button, as this knob can be caught with stray fingers etc. The LFO depth also has a dedicated knob. one slight grumble is that the range of values implemented for the tap tempo modifier mean that the maximum length of 1 LFO wavelength is 1 bar. This means that a slower half speed or quarter speed tempo has to be manually tapped in to achieve longer wavelengths.

The final section is the output section which includes a bypass switch, a rotary pot to set the mix, clip and midi led indicator lights. This section is perhaps the weakest, and I would have liked to see a full range stereo VU meter (I know how easy these are to add - I guess it was to keep the cost down, but I would be willing to spend an extra twenty pounds for good metering.), and also the power switch and midi channel selector switches in this section on the front plate, rather than round the back of the unit. The main problem with them being round the back is that once you have your unit rack mounted, you either have to unscrew it to turn it off, or simply unplug it from the mains, neither of which are options I like!

This is an example of a piece of equipment which on paper looks very ordinary, but which is greater than the sum of its parts. The filter section for example, on its own although it sounds smooth but unpowerful, although this makes it perfect for subtle adjustments. Having the LFO and envelope follower add extras features which are fantastic to play with. You can't help but twiddle the knobs on this unit (!) it is very tactile and enjoyable to mess with! Almost any sound that goes through it sounds fat coming back. Some of my favourites are sub basses with full buzz, and the high end rolled off to cut some of the high end harshness (Lo-pass), and drum breaks through the envelope follower, with lots of buzz, and the cutoff at about 10'o'clock (band-pass). Lovely crunchy Aphex style beats straight away.

The midi implementation of this unit is also stunning, and should be used to its full. Every knob sends out and receives midi, which makes life much easier for automating those filter sweeps on your breaks. Also, the settings which aren't knobs snd and recieve. There are two things to note about the midi on the filter factory. Firstly, the channel selector switch is not exactly accurate and it took me a while to work out what number it is actually pointing at. In the end I found it by simply sending midi on different channels and seeing when the receive led lit (but then it's done). The second thing is that if you have a setup you like with the unit, make sure that you define these settings in your sequencer package's midi page. If you don't, when you send it automation, all kinds of strange things will happen! Exponent tip: Initialise all the values for you have automated on a blank bit of midi track at the beginning of the tune, otherwise, depending on your sequencer, it will play back with the last settings it was sent until it recieves new automation for those controllers.

For live use the unit is incredible. It's knobs are big enough to see and stand out from the green case. It also has a few features that make it FUN, like the engage buttons (also midi controllable), which enable you to bypass just the Buzz section of just the filter, or for a momentary drop of these circuits hold the 'momentary button', which reverses the current setting of the engage control while it is held. It reponds instantly aswell, so you can flutter the effect nicely. I have not seen a DJ use one, but if you are a DJ then I seriously recommend getting one and running one deck straight thru it to the mixer.

So what are the downsides? Well the fact that it is no longer produced is one. The others are the midi selector switch, the lack of metering, and the power switch on the back. The only other issue that this unit has is that with the buzz turned up, there is a lot of noise. But then it is up to you if this is a problem (I personally am willing to put up with it). (As my university lecturer used to say - "Noise is only a problem if you can hear it", although with the music we write noise is always a welcome guest! and if you don't take the mickey with the Buzz level, it's better described as 'warmth').

This is one of my favourite pieces of outboard (shame I have to give it back soon) and I would recommend it to anyone who is in the market for a smooth sounding analogue filter. [ exp_cj says: hehehe, sorry mate, I NEED to use it on tunes...all the time..... but you know it's yours when you need it, cos I understand it is essential ]

CAUTION: Be very careful not to overload your speakers since the level that the filter factory goes to is extreme. If you find the level is too much, try taking off the Buzz.

FOOTNOTE : - We have heard that the smaller version of this filter (the filter queen) has a few reliability issues. Apparently the cutoff and resonance controls develop bad crackle problems after a couple of months, the lack of midi impairs it, and the filter itself is underpowered. The crackles have not been a problem for the filter factory after a year of near constant use, however. We also stress that this is just a rumour from one or two users who may have just overloaded it and we recommend you seriously consider it if you can't afford the larger version.