Sintefex FX2000 & CX2000

What if you could access the sound and controllability of a range of the best-known classic analogue compressors and EQs, from a single rackmount box, in the digital domain? Two advanced processors from Sintefex aim to offer just this ability.

Still a relatively little-known manufacturer, Sintefex produce some of the most advanced digital signal-processing equipment currently available. Although the product line-up is small — Postman Pat could count the units on offer on the fingers of one hand — the three members of the present family provide a sensible and useful range of facilities. The flagship that started it all is the FX8000 'Replicator' — not some Jurassic dinosaur, but a highly advanced convolutional processor employing anything up to 37 SHARC DSP chips and an internal 3Gb hard drive.

Photo: Mark EwingThis intriguing machine is able to reproduce the signal processing of virtually any conventional signal processor, irrespective of whether it is producing a 'static' effect such as EQ, or a dynamically changing one, such as compression. Indeed, it is the machine's "Unique Dynamic Convolution Technology" that enables it to fully replicate the characteristics of a wide variety of analogue signal processing, where the response changes with amplitude — and that is something which plays a key part in the sound of a whole host of valve equipment, for example.

Most convolution devices — the Sony and Yamaha sampling reverb machines, for example — base their convolutions around the results obtained from an impulse generated at a single amplitude. Many separate impulses may be combined in order to reduce the noise floor, but a single impulse amplitude is employed. In contrast, the Sintefex approach is to employ impulses at 127 different levels, so that the performance across a wide range of operating levels can be captured. In this way, the frequency response changes with increasing amplitude, and the increasing distortion of valve units can be measured and replicated with remarkable fidelity. While the concept may seem simple enough, the physical implementation is extremely complex, and I know of no other commercial product capable of this finesse.

The Sintefex flagship machine ships with a large collection of preset convolution samples of various classic equalisers and dynamics processors, but it is also equipped with all the necessary test signals and facilities for the user to sample favourite audio processors and create new convolutional samples. This data can also be shared over the Internet, and the Sintefex web site already contains libraries of submitted processors for free download.

OK, so it's an impressive box — but you may still be wondering what the point of it all is. Well, there are several. For a start, classic equalisers and compressors are inherently scarce and expensive, and often less reliable than would be desirable. As such units were designed in the days of mono recordings, finding two examples matched closely enough for accurate stereo tracking is also a pretty tall order. Furthermore, in the increasingly digital world, the latency involved in exiting a digital console, passing through a classic analogue processor, then returning to the digital domain, can be problematic.

The original FX8000 Replicator is the basis for both the FX2000 and CX2000.However, once a suitable vintage analogue processor has been sampled accurately into the Replicator, the characteristics of its captured signal processing are locked in, with near-perfect and completely repeatable quality, complete with all the non-linear and distortion characteristics that define the warm, complex analogue sound of the original device. Better still, the data can be replicated on multiple channels and cross-linked for utterly precise tracking in stereo or multi-channel applications.

There is also a major space advantage: a single 2U rackmount Sintefex box can effectively replace a complete rack's worth of Fairchilds, Pultecs and dozens of other classic processors. You can't use them all at once, but you probably wouldn't want to anyway. The reason big studios have racks filled with these vintage toys is that their unique characteristics add to the musicality of some sources better than others, and so whereas a Pultec might be the perfect processor for one job, a Fairchild might be better for another. The Replicator allows the same degree of flexibility, but without the cost, maintenance and space overheads.

Chips Off The Old Block

You will have noticed that while I have been raving about the Sintefex flagship FX8000, this review is actually all about two different units, the FX2000 and CX2000. However, there is (some) method in my madness. The Replicator represents the state of the art in commercial convolutional processing, and affords a wide range of facilities and features — not the least of which is its ability to provide processing across eight simultaneous audio channels. Consequently, it is an expensive beast and may well represent too big a first step for many to take down the convolution road.

The 2000 models have been designed to offer exactly the same convolution processing as the FX8000. However, some of the bells and whistles of the flagship have been cast overboard in order to make these junior machines far more affordable — and therefore more attractive, even to the techno-sceptics of the studio fraternity.

As you might surmise from the numbering scheme, the first simplification is that these are both dual-channel units only. They can be used as either dual-mono or stereo processors, but there is no provision for multi-channel operation within each unit (although multiple units can be linked for multi-channel applications, if required). Similarly, whereas the Replicator was equipped with both analogue and digital I/O, the 2000 models offer analogue interfaces only as an extra-cost option. There are a number of other less vital digital interface omissions too, such as the absence of an AES reference input (although a BNC word clock is still provided) and no dedicated S/PDIF coaxial or optical I/Os, nor an ADAT interface.

A far more significant omission — and perhaps the most important — is that these junior machines omit the FX8000's self-sampling technology. So they can reproduce the characteristics of preset or custom-loaded processor samples, but cannot be used to sample the user's own equipment. However, I suspect such a compromise will be of little concern to many (even most) users. Sampling a complex processor is an intricate business and best left to those who have the time, understanding and experience to do the technology justice.

So much for the generic differences between the 8000 and 2000 models, but what about those between the FX2000 and CX2000? The FX2000 is based fairly closely on its big brother, the FX8000, and shares a similar internal technology (including the hard drive), front-panel layout, and large monochrome LCD screen. Aside from the I/O differences and the absent self-sampling facilities, these two machines are quite alike in functionality and capability; FX8000 programs can even be downloaded and used directly in the FX2000. Consequently, the full range of classic dynamics and EQ processing is available, including the unique Sintefex 'Power Linear' EQ mode. The Power Linear mode modifies the EQ convolution data to provide true linear phase responses — something that is physically impossible to achieve in the analogue world, and that changes the sonic character of a given EQ quite dramatically. Clearly, engaging the Power Linear mode is a nonsense if you are trying to replicate the sound of a classic vintage equaliser, but if you are looking for a unique and interesting sound character, this is a very handy and creative feature.

By way of contrast, the CX2000 is a radically different contraption. It not only looks completely different, with a slim 1U chassis and a small green fluorescent display, it also dispenses with the hard disk for data storage, and is also minus the classic EQ programs of the FX2000. Instead, it offers only a range of well-known compressor samples — although this is a blessing in some ways, as the user interface has been streamlined to suit this specific purpose, and is somewhat easier and faster to operate as a result. If you thought the missing hard drive and smaller PSU would mean a quieter, fanless machine, you're set to be disappointed. There is a noisy little high-speed fan mounted towards the front of the right-hand side panel, and although the noise is subdued slightly when the unit is installed in a rack, it may still prove a problem in quiet rooms, and cannot be turned off as far as I can see.

Although the convolutional EQ programs have been dispensed with, the CX2000 does incorporate a digital three-band parametric EQ section (a facility absent from the FX2000), which can be allocated pre-dynamics, or in the dynamics side-chain, as necessary. The CX2000 cannot load FX8000 programs directly, although new programs derived from the same convolutional technology can be imported through its USB and MIDI ports to extend its sample range.

The FX2000

Sintefex describe the FX2000 as an "Analogue Sound Stereo Digital Classic EQ/Compressor". That's a bit of a mouthful, but it sums up very accurately what is on offer here — numerous well-known classic outboard and desk equalisers and compressors. The review machine provided 44 sampled equalisers and four digital parametrics, plus 72 compressors. However, each device is presented at four different sample rates (44.1, 48, 88.2 and 96kHz), so in reality we have 12 equalisers and 18 dynamics processors, which is still an impressive rackful! In addition, there are several amplifier and speaker samples, reverb samples and various other useful effects — see the 'FX2000 Sampled Processors' box for a detailed listing.

Sensibly, the preset selection menu allows presets to be sorted according to both sample rate and separate memory banks, which removes the inherent program duplication that might otherwise cause confusion. There are eight banks, each with 128 memories, some of which are pre-loaded from the factory, but all are accessible to the user, both for recall and for saving of new or updated programs.

The review FX2000 was fitted with the optional analogue I/O, on four XLRs. AES-EBU digital I/O is provided as standard.The front-panel controls are well spaced and clearly labelled, and I found operation of the machine entirely intuitive. Moving from left to right, a software-controlled power button is followed by another button, labelled 'Input View'. There are several 'View' buttons, and these recall the appropriate menu page to the display. In the case of the Input button, the menu allows analogue (if installed) or digital inputs to be selected (independently for each channel if required), and shows input and gain-reduction meters as horizontal bar-graphs. There are two analogue input modes, one with a DC-removal filter (-3dB at 1Hz!) and one without.

A rather nice touch is the provision of a 'Big Meters' mode, which fills the screen with a pair of superb virtual VU meters, one above the other, showing the input levels of the two channels. Other sub-menus allow the analogue VU and digital bar-graph meter reference levels to be adjusted, as well as the analogue input sensitivity over a ±6dB range. Intriguingly, the meters show levels above 0dBfs, which may seem a little odd in a digital processor. The reason is that the machine has a huge internal dynamic range, and if a signal is boosted in level — perhaps through heavy equalisation — it will remain perfectly intact even if it exceeds 0dBfs internally. However, it will be too loud to squeeze through the output port, so the output-level control has to be used to bring the signal peak back below 0dBfs for output through the AES or analogue ports. If the analogue option is installed, the nominal analogue I/O level is +18dBu for 0dBfs, although this can be adjusted through internal links to anything between +10 and +24dBu. The internal A-D and D-A converters are both 24/96 capable, and the AES interface supports single-wire, double-rate data for 88.2 and 96kHz operation.

The next section is concerned with the Equaliser mode, and contains another View button which allows the user to see what processing is currently active and to modify it as necessary. Two further buttons, both with associated LEDs, access 'non-linear' mode and turn the section on or off (bypass). The non-linear switch enables any non-linearities of a selected sample to be removed, resulting in a more uniform response regardless of how hard the equaliser is driven. Although moving away from the accuracy of a sampled process, this is useful if the non-linear distortion is distracting or unsympathetic to the audio being processed, and further expands on the versatility of the FX2000. The same switch also controls the non-linearities of classic dynamics processing when the classic EQ is not in use.

The compressor section boasts the same View and Section On (bypass) buttons, and supplements them with Link and Pre-EQ switches. The first links the processing in the two channels for accurate stereo tracking, while the second allows the order of EQ and dynamics processing to be reversed.

Before the display screen and its four associated 'soft buttons' is a group of four switches. These provide Channel Select and System bypass functions for the two channels. The first allows independent control and adjustment of each channel: by holding one and pressing the other, it's possible to activate or disable the stereo-ganging function. The 'System On' switches act as bypass buttons for the entire channel, as distinct from the section-bypass buttons mentioned earlier.

The four buttons along the left-hand side of the LCD are labelled Option Select, and their functions vary according to the menu functions displayed. This part of the design is completely familiar and intuitive. The screen menus can be navigated with a group of four cursor keys to the right of the display, and any highlighted parameter may be adjusted with the data encoder knob. Finally, there's an output gain knob to allow hands-on access to output level — although it is possible to disable this control in the Setup menu if required.

Taking a quick look at the back of the machine, the review unit was fitted with the analogue I/O option, which occupies four XLR connectors. The dual-channel AES input and output employ another two. A pair of phono connectors provide a digital gain-linking bus which allows multiple FX2000s to be ganged together for multi-channel applications. The BNC socket accepts a word-clock reference, and remote control and software updates are catered for through a pair of MIDI sockets (In and Out) and a USB port. There is a power on-off rocker switch adjacent to the IEC mains inlet, and the power supply features a cooling fan. There is also a little noise from the internal hard drive, although this will spin down after a period of inactivity.

For the number-junkies, the FX2000 contains 10 SHARC DSP chips providing 800Mflops per channel. One of the chips administers the system and I/O interfaces, while the other nine provide the convolution engine. The processing delay through the machine varies depending on the convolution being performed, but is rarely more than a couple of milliseconds. To make bypass comparison easier, the machine can be set up to insert a matching delay when in bypass, and a fixed delay mode ensures a maximum delay of 150 samples regardless of the processing selected in either channel. Having said that, the Power Linear mode, which introduces linear-phase filtering, imposes a much larger delay — typically 2000 samples (about 40ms, or a TV picture frame at a 48kHz sample rate) — and this cannot be matched by the system for bypass purposes.

FX2000 In Use

The FX2000 is quite straightforward to use, and after a few minutes of playing around I was happily applying and manipulating all sorts of classic EQ and dynamics processing with various test tracks. The controls and screens are really optimised for the EQ and compression functions, which makes operation pretty intuitive. Although all the sampled EQs and compressors share the same graphical screen elements — multi-faceted bakelite-style knobs and a detailed VU meter, for example — the arrangement of controls and their labelling reflect those of the original machine. The Pultec EQs have frequency controls labelled in CPS and KCS (cycles per second and kilocycles per second), for example.The resolution of the controls is obviously dependent on the accuracy and thoroughness of the original sampling, but in every case I found them to operate as expected. A slight distraction is that the knob images have relatively few rotary positions, but the actual control increments are much finer (often down to 0.1dB steps), and the resolution was always fine enough for what I wanted to do.

The classic compressor pages all feature smaller virtual knob graphics, which can be combined in various ways with virtual VU or bar-graph gain-reduction meters, and/or a transfer curve showing the shape of the knee and slope angles. Again, as with the big input-meter mode, the gain-reduction meters can be made to fill the entire screen, which proved very useful when I was sitting across the control room from the Sintefex box. These large virtual VUs really are impressively done, and most of my colleagues who saw the machine did a double take and had to get up close and personal to verify that this really was an LCD!

In the case of the more diverse samples cloned from the FX8000, while this simpler machine could use them well enough there are no facilities to edit the parameters, so you have to take what is offered — which is usually just fine, anyway.

The CX2000

This is very much a second-generation machine, with a radically different control-panel layout and a green fluorescent display in place of the monochrome LCD. It takes a little getting used to after the FX2000, but is clear enough once you realise that the display legends are printed above and below the screen on the panel metalwork.

Sintefex CX2000.When the CX2000 is operating as a compressor, the display shows five knobs, with black dots to indicate their position, and numeric readouts immediately below. The legends printed on the panel above reveal that these virtual controls represent Threshold, Slope, Attack, Release, and Gain. Below these controls is a gain-reduction meter, again with the scaling printed on the panel below. The meter scale extends to -60dB, although in use the area below -10dB is occupied by part of a description of the compressor. However, if the amount of gain reduction encroaches on this area, the text disappears and the meter scale is extended.

Some of the physical controls are similar to those of the FX2000, especially those on the right-hand side which select the channel for configuration and operate the bypass modes. A pair of Link buttons is provided: the bottom one links between the two internal channels, and the upper one extends that linking to a second CX2000 for multi-channel applications.

The majority of the panel is dominated by five rotary encoders which relate to the virtual knobs shown in the display. Some users may find a translation problem here, as there is quite a distance between the graphics and their associated knobs. I have to admit to often twiddling the wrong knob while looking at the screen (not sure that came out the way I had intended!).

Again, our CX2000 had the analogue option fitted. New programs can be imported via the USB and MIDI ports.The biggest difference between the operation of the CX2000 and the FX2000 is in the setup and configuration controls. There are four black buttons just to the right of the display. The top two are labelled 'Menu' and 'Do It', while the bottom two are left and right cursor keys. Pressing the Menu button reveals a series of labels below the knob graphics, which can be scrolled with the cursor keys. The current selection is enclosed within a box outline and pressing the 'Do It' button recalls that particular menu to the screen. The options cycle around the input and output level setting, expander-gate function, side-chain EQ, load compressor, load program, save program, sample rate, clock source and input source.

For most menus the first encoder knob is used to scroll through and select the desired option, which is confirmed with the 'Do It' button. It is all frighteningly obvious once you have played with the machine for a few seconds.

On the review machine, there were no programs loaded (at least, none I could find), but there were 12 compressor samples on-board, which included the black-face Urei 1176, the Fairchild, Teletronix, dbx, and other classic devices already mentioned in the context of the FX2000. They all worked as well and as precisely, but I actually found the CX2000 to be slightly easier and faster to set up and use.

Conclusions

Both of these processors are impressive in their performance and controllability. The sampled classic EQ and compressors certainly seem to have all the characteristics and facilities I was expecting, and being able to call on such wonderful recreations of products with a few button clicks — as well as being able to access them while staying within the digital domain — is superb.

The two machines are easy to set up and use, and the display of the FX2000, in particular, is wonderful. The reduced capability of the CX2000 does not bother me; many engineers would gladly buy a CX2000 simply for access to its range of classic dynamics processors. The FX2000 takes things a stage further with the addition of the classic EQ, and because its processing is derived from real samples of the original machines, adjusting the high end is completely devoid of the 'digital sound' associated with traditional digital EQ algorithms. The linear phase mode is an interesting facility too, with new and unfamiliar sound characteristics which are worth experimenting with if the additional delay is not an issue. The only real downside, as far as I can see, is fan and drive noise (in the case of the FX2000), although with so much DSP power inside these boxes it is hard to see how this problem could be solved.

If you have a hankering for a rack full of vintage outboard, but either don't have the space or the funds, these Sintefex units could well be the solution you have been looking for.