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Electrix Filter Queen & EQ Killer

Electrix Filter Queen & EQ Killer

Electrix's new babies may look like Day‑Glo '50s Bakelite radios, but they are in fact an innovative pair of pint‑sized studio processors. Paul Farrer gets out his magnifying glass...

Electrix are not a company to fit in with the norm, it seems. The Filterfactory and Warpfactory launched their unique take on signal processing (see review back in SOS October 1999), combining DJ‑oriented performance controls with a funky colour scheme and a light show worthy of Las Vegas. The MoFX continued the madness with multi‑band flanging, tremolo and tempo‑related delay (see SOS July 2000), and now two new diminutive processors have joined the range.

The Filter Queen is the first of these, and provides real analogue filtering, controllable either manually or via an internal multi‑waveform LFO and frequency‑selective envelope follower. It is this which will be the main subject of this review. The simpler EQ Killer is a frequency‑crossover unit optimised for creative use — see the 'Kill Or Be Killed' box for more details.

The Royal Tour

The two half‑rack units can be comfortably racked together, though individual power supplies are still required for each.The two half‑rack units can be comfortably racked together, though individual power supplies are still required for each.

The Filter Queen is well‑stocked with both inputs and outputs. The rear of the unit features stereo pairs of inputs and outputs on both phonos and unbalanced quarter‑inch jacks — an adjacent switch selects between nominal operating voltages. There are two additional jack sockets, one for a momentary footswitch (which allows the user to remotely bypass the effects) and the other for a pedal controller (which controls the filter frequency). Another rear‑panel button toggles between stereo two‑pole and mono four‑pole filter settings — the former offers a stereo signal path with 12dB/octave filtering, whilst the latter offers a steeper filter response of 24dB/octave but with only a mono signal path.

Moving to the front panel, on the extreme right‑hand side there is an LED power indicator and two small, dual‑colour LEDs representing input and output signal levels. As always, the perfect settings require that these glow mainly green, only very occasionally peaking into the red, and they do the job well enough — but is it really too much to ask for a full set of VU indicators at this price point? The mix levels are serviced by a single knob, determining the ratio between input signal and effected output.

Magic Momentary

The rear panels of the Filter Queen (above) and the EQ Killer (below).The rear panels of the Filter Queen (above) and the EQ Killer (below).

Activating the filter is possible from either the Engage or the Momentary buttons, both of which are backlit. Engage switches the filters in permanently while the larger Momentary button allows you to flick the filter effect in and out — it is only activated as long as you keep the button depressed. Alternatively, when the Engage button is activated, pressing the Momentary button will temporarily disable the effect.

The way in which these two buttons work together really encourages sonic experimentation, and this cute design idea has to rate as one of the best I've seen for a while. However, the Momentary button was occasionally prone to producing a slight but distinctly audible high‑frequency click as the effect punched out — though this is hardly likely to upset huge numbers of users at this price.

The filter is controlled by two switches (similar in size to the main Engage button) and seven large knobs. The feel of these control knobs is really professional, and clear labelling makes recalling previous set‑ups and keeping an eye on edited values a doddle.

The Filter Queen offers four different types of filter: Low‑pass, High‑pass, Band‑pass and Notch. You select which one you want using the Filter Type button and your selection is indicated with one of four LED indicators. Anyone who has ever played with an analogue synth will know that Frequency and Resonance are the two most 'twiddled' controls, and the Filter Queen's knobs are therefore larger than all the other front‑panel controls. The filter frequency can be swept from 20Hz to 20kHz, and the resonance is, unusually, adjustable from ‑2 to +10. The negative resonance values give the Notch filter a more pronounced sound, while making all the other filter responses less pronounced. As for the maximum positive resonance, it's certainly very characteristic, but you can't get the filter to self‑resonate.

The envelope follower controls the filter frequency depending on the setting of the leftmost two knobs: Depth adjusts how much the filter will follow the dynamics of the input signal, and Release can be used to 'smooth' the Envelope Follower's response, essentially determining how percussive the filter effect sounds. The frequency bands that the Envelope Follower tracks can be specified using the Band button, which cycles around all seven possible combinations of Low, Mid and High bands, the current status indicated by the LEDs above it.

The controls for the internal LFO are similarly uncomplicated. The Depth control works in much the same way as it did for the envelope follower, while the Speed knob sets the LFO rate. The Waveform selector button completes the LFO facilities, offering sawtooth, inverse‑sawtooth, triangle, square and random waves. As a handy bonus, the associated LEDs which indicate your choice of wave type flash in time with the speed of the LFO, even if the depth control is set to the Off position.


Electrix Filter Queen & EQ Killer

The wonderful thing about filters is that, although they may sound technically daunting, even a child of six can get a huge amount of experimental mileage out of them simply by tweaking and fiddling. The Filter Queen may come in an unconventional box, but it provides a great analogue filter sound with the minimum amount of fuss. Don't be put off by the price tag either — this unit manages the rare trick of exuding professionalism and excellent sound quality while also providing wild, hands‑on, sonic fun. Obviously designed to go hand in hand with the EQ Killer, there are many who would argue that Electrix should have stuck the two units together as a single device from the start, but I'm beginning to see the logic of this split approach. The Filter Queen has a huge number of potential users, whereas the EQ Killer, for all its natty cleverness, has a slightly narrower appeal and is perhaps much more likely to interest the remixer or DJ. Together, however, they do make an undoubtedly enviable addition to any studio rack and the option to buy just one or the other (or even two Filter Queens) without having to invest in features that you don't need can only be good for the consumer.

Tower Of Power?

Both the Filter Queen and EQ Killer are powered from separate 16V external power supplies. An immediate gripe is that, assuming you opt for both units (and obviously Electrix are hoping that you do!) you'll need a cumbersome wall‑wart PSU for each half of the resulting 19‑inch rack unit, as there is no way to feed both units from the same power supply. This is a real shame and it could have been remedied by including a Power Thru socket for daisy‑chaining the power.

Kill Or Be Killed

The ability to remove sonic elements from a track — particularly the bass drum — can be very useful when wishing to mix tracks together within a club environment. It can also be handy when remixing if you have no clean section of source track to work with. The EQ Killer is designed to deal with exactly these kinds of task, using a pair of powerful adjustable crossovers to split the audio signal into three bands.

The unit's rear‑panel socketry allows two separate devices to be wired to the unit independently. Understanding that the features on offer here are most likely to be needed by DJs for beat matching and more harsh EQ functions, the EQ Killer allows direct patching (via phono sockets) to the outputs of a turntable or CD player, with a small button next to each set of inputs boosting the signal if coming from a turntable. There is also an FX Loop in the form of two sets of phono input and output connectors, which allows you to send the EQ'd signal to another processor unit, returning the processed signal to the EQ Killer's outputs.

Moving to the front, we find an essentially simple layout of three Level controllers, each of which adjusts the volume of one of the frequency bands. These are centre‑detented when the knob is vertical. Each of the three bands can be muted using the dramatically labelled Band Kill button. As with the Filter Queen, there is a Momentary button for each band allowing quick and spontaneous activation and deactivation.

The two crossover‑frequency controllers allow you to select the width of each band on the unit, Low X‑Over specifying the transition point where the low band ends and the mid band starts, and High X‑Over defining where the mid band stops and the high band begins. The only other button on the front panel toggles between inputs one and two — if only one input is connected, this acts as an EQ bypass.

Finding the exact point at which you need to roll off the bass end of a track is made a remarkably easy task by the EQ Killer, though how good it is at stripping other frequencies from a full mix really depends on the type of music you are looking at. Obviously there hasn't been a piece of kit invented yet that can effectively remove a sound such as a vocal from a track, but with this unit you can go some considerable way towards reducing the level of elements within a complete mix.

What EQ Killer reminds us of is the power of equalisation as a creative tool rather than just something useful for 'adding a bit of top'. It encourages experimentation more than nearly any other piece of equipment I can think of in my studio at the moment. The professional feel of the unit as a whole, coupled with its clear layout and well illuminated buttons, make the EQ Killer a very worthwhile piece of kit to have about.


  • Professional feel and solid build.
  • Easy to use.
  • Good value for money.


  • Individual wall‑wart power supplies required for both units, even when racked together.
  • Limited metering.
  • Occasionally audible click when using filter's Momentary button.


A pair of extremely user‑friendly and inspirational outboard units that deserve to do well. The performance‑oriented features will gain them respect with DJs and live musicians alike, while the sound quality and intuitive control should also win favour with studio users.