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Tonelux Equalux

Dual-channel Parametric Equaliser By Hugh Robjohns
Published June 2010

Better known for their high‑end modular outboard processors, Tonelux have scaled their EQ up to full rack size. Does more space mean a better feature set?

Tonelux Equalux

Tonelux are an American company who are probably best known for their Roadster V‑Rack system of configurable audio-processing modules, designed by Paul Wolff. Superficially, the V‑rack system is similar to the API 'Lunch Box' concept, but it isn't actually a compatible variant. I reviewed the Tonelux V8 system and some core modules in SOS January 2009 (/sos/jan09/articles/toneluxv8roadster.htm).

In an inevitable departure from this impressive modular format, Tonelux have recently launched the first in a new line of rackmount signal processors based on the same proven circuitry as the modular units, starting with the Equalux — a two-channel, four‑band equaliser based very closely on the EQ4P V‑rack module. A dual mic preamp and dual compressor are planned to follow.

As with the V‑Rack review, there was no manual supplied with the Equalux — Tonelux apparently still don't 'do' manuals — and there were few details on-line, but at least the unit is relatively straightforward and logical to operate, even if the inner workings remain something of a mystery!


The 19‑inch, aluminium, 1U rack case extends about 280mm behind the rack ears and access to the internal circuitry, should it ever be required, is by removing three screws and sliding the lid off. Doing so reveals a simple, linear power supply, extending the full depth of the case on the right‑hand side (the V‑Rack system uses a universal switched‑mode supply). Two identical audio boards also stretch the full depth of the case, with the I/O connectors at the rear and some of the panel switches at the front. A few small daughterboards, additional front-panel switches and ribbon cables interconnect the various PCBs. While the audio circuitry is similar to the EQ4P, clearly these are newly designed circuit boards, which are very different to the rack module designs and include local power-supply regulation.

The audio equaliser circuitry for each channel is based around six Burr Brown 'SoundPlus' OPA2134 high-performance dual op‑amps, while a couple of discrete custom amp modules appear to handle the input stages. The same TX260 discrete output stage and transformer is used as in the EQ4P rack module. Conventional components are used throughout, and all ICs are socketed.

The rear panel carries XLRs for the balanced line‑level inputs and outputs operating at a nominal +4dBu, but there is also a TRS socket on each channel, providing a nominal +10dBu input to accommodate high‑output D‑A converter signals. This feature has been carried over from the V‑rack module system and is a very good idea. Power is hooked up via the usual IEC inlet, with integral on‑off switch and fuse holder. The unit operates with a factory‑fixed mains voltage, and there's no user‑configurable alternative.

The front panel follows a similar layout to the EQ4P module, with four independent EQ bands, each providing up to ±15dB of gain range on the lower, silver, centre‑detented, dual‑concentric, rotary control, and continuously variable centre frequency selection on the upper, black, dual‑concentric control — just as with the EQ4P module. However, the four band 'peak' push-buttons have been moved above their respective rotary controls instead of being placed between them, while the channel 'In' and Bypass buttons have been moved to the centre of the panel, between the two channel sections.

The rear panel follows a familiar formula, which includes an IEC power inlet, inputs on balanced jack and XLR, and XLR analogue outputs.The rear panel follows a familiar formula, which includes an IEC power inlet, inputs on balanced jack and XLR, and XLR analogue outputs.Starting at the left, the first push button converts the low‑frequency band to shelf mode, and the frequency range spans 18Hz to 1kHz. When active, the shelf‑mode button is illuminated blue, and the low band's peak button is disabled. If working as a peaking equaliser band, the peak button lights up yellow when activated in 1/3‑octave mode.

The lower-mid band is tuned a little higher, to cover 50Hz to 3kHz. The two upper bands both span the same range, from 500Hz to 21kHz, but the top band can also be switched to a shelf mode if required. Again, the shelf button lights up in blue when it's active and the corresponding peak button is disabled. These frequency ranges are all essentially the same as the EQ4P module, but the low‑band shelf mode is a new addition — and a most welcome one.

The 'peak' buttons for each band select a constant 1/3‑octave bandwidth mode and are illuminated yellow when active. The default 'proportional Q' or 'constant energy' mode means that as the amount of cut or boost is increased, the bandwidth over which the gain acts is reduced. This makes for very intuitive equalisation, as small boosts or cuts affect relatively wide frequency ranges and so sound gentle and subtle, while heavy EQ becomes progressively more precise and localised.

In the centre section, separate buttons are provided for each channel, to switch the EQ in and to provide a hard bypass. The 'In' button (red when switched out) allows the effect of the equalisation to be compared with the raw signal by switching the EQ circuitry in and out of the signal path — although the input buffers and output transformer are still in circuit. A nice feature is that when it's switched in, the button lights in green, with varying levels of brightness to indicate the signal level. An internal jumper link allows this signal to be derived from either the EQ stage input or output. The Bypass button does what it says: it provides a relay‑switched hard bypass of the entire unit, linking the input directly to the output. A front-panel power on‑off button occupies the extreme right‑hand side of the unit, and must be pressed in addition to the rear-panel rocker switch.

In Operation

I had found the original EQ4P module a little fiddly to operate, simply because of the density of controls, but the Equalux is a little better in that respect — although slim fingers are still a definite advantage! Like its forebear, the Equalux is capable of both gentle tonal shaping and surgical, corrective EQ applications, and the generously overlapping frequency ranges across the bands ensure that multiple bands can be brought to bear in difficult situations. The proportional‑Q design is very intuitive and easy to use, while the fact that a fixed bandwidth mode is also provided increases the flexibility of the unit considerably.


The Equalux is a fine‑sounding equaliser, adding a subtle but pleasant coloration to the sound, thanks to the output transformer and discrete amp stages. It clearly follows closely in the footsteps of the EQ4P rack module, sharing the same sonic signature and feature set — although the addition of the LF shelf is a definite bonus. Choosing one version over the other is largely a matter of practicality and preference: modular systems are initially more expensive, but ultimately more versatile and space‑efficient; whereas rack mounting is more cost effective and potentially easier to use, since the panel space is significantly greater.

This is a high quality, high‑end processor with an excellent pedigree, and is certainly well worth auditioning if you are in the market for a very capable and versatile bus equaliser.  


Outboard equalisers come in a wide variety of guises and prices, but worthy competitors would include the likes of the API 5500 Stereo EQ at the higher end of the marketplace, the DAV BG3 stereo mastering EQ at the lower end, and the Neve 8803 dual‑channel equaliser in the middle.


  • Four nicely overlapping bands with switchable bandwidth options.
  • High and low shelf options.
  • High‑level input to cope with pro D‑A outputs.
  • Neat input-level metering on 'EQ In' button.


  • Slightly cramped controls
  • No user‑configurable mains‑voltage options.


The Equalux is a very versatile, high‑end, dual‑channel equaliser with an excellent feature set.


£1468.75 including VAT.

Unity Audio +44 (0)1440 785843.


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