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Apogee Trak 2

Mic Preamp & A-D Converter
By Hugh Robjohns

Apogee have an enviable reputation for their state‑of‑the‑art digital converters, but their new Trak 2 also includes sophisticated mic preamplification.

Apogee are virtually synonymous with A‑D and D‑A converters. In fact the company's pedigree dates right back to the start of the digital age in the early '80s, with the manufacture of replacement and OEM anti‑alias and reconstruction filter stages. However, although the new Trak 2 retains the large silver buttons and purple livery which have come to define the Apogee brand style, it is far more than just another converter package. And whereas countless companies have produced mic preamps of varying sophistication with integral digital outputs, Apogee have approached the market from the opposite direction, creating a flexible digital converter (with up to eight internal signal busses) incorporating a versatile mic preamp.

Trak 2 Facilities

Apogee Trak 2 front panel.The front panel is wonderfully simple, because the unit is controlled entirely through a graphical user interface presented on a 240 x 66‑pixel backlit LCD panel. The on‑screen menus are navigated and adjusted through the familiar and intuitive paradigm of an encoder wheel and a quartet of cursor buttons. Two further buttons may be user‑programmed to access directly the two most frequently required menu pages. The two remaining buttons switch the power on and off, and configure the metering. The latter, located under the bar‑graph meter, resets the peak‑hold LEDs and, if held depressed, switches the metering to provide a useful stereo phase correlation display.

Two rows of five LEDs to the left of the bar‑graphs provide clear indication of the current status of each input channel, with lights for (analogue) input clipping, phantom power, polarity reversal, insert mode (see below), and auxiliary inputs. The level meters normally span a 50dB range, with separate Over lights, but there is also a ±1dB mode to enable precise level calibration. Various meter responses may be selected, including peak reading, or combined peak and average reading. Metered peaks can be held for two seconds or until reset.

It is hard to pigeonhole the Trak 2, because it can be used in so many different applications, with a wide range of optional interface cards — every owner will probably find a subtly different way of using it. For a start, it can serve just as a high‑quality dual‑channel mic preamplifier with analogue outputs, or as a high‑impedance DI box providing balanced line‑level outputs from electric guitars, for example. The A‑D stage can be used entirely independently too. Alternatively, it can be used as complete recording channel to feed a mic to a digital recorder.

Although there is a dedicated D‑A converter built in for feeding a monitor headphone socket on the front panel, the standard Trak 2 does not contain a high‑quality D‑A stage. However, there is provision to install either a stereo or eight‑channel D‑A if required — and this can be used independently of the rest of the package too. The other user option is to install up to two AMBus cards (see the 'AMBus Options' box for details), which allow the Trak 2 to take on the role of a digital format converter or a complete I/O interface for a digital audio workstation. A sample‑rate converter card is also planned for the future.

Onboard digital signal processing is available in the form of Soft Limit and Soft Saturate functions (although only one of these is available at a time). The Soft Limit can be used to protect against transient overloads and thus extend the effective headroom, while the Soft Saturate (reintroduced from the old AD500 system) emulates tape‑saturation or valve 'warming', which may be useful during tracking.

The Trak 2 would also be useful in mastering applications, not only as a high‑quality converter, but also by using the Soft Limit function to provide a few decibels of extra loudness. In addition, the UV22HR bit‑reduction algorithm — highly regarded throughout the mastering industry — allows high‑resolution 24‑bit recordings to be reformatted for 16‑bit media whilst retaining most of the low‑level information.

Finally, the stability of Apogee's crystal‑based word clock is such that the Trak 2 can also be used as a master clock source to improve the performance and resolution of connected budget digital equipment. It can even synchronise word clock to a video reference with the optional video‑sync card installed, making the Trak 2 an ideal component in small video post‑production areas or in studios involved with music for picture.

Incidentally, Apogee have also just released some bespoke software for Mac computers, which allows full remote control of the Trak 2 using MIDI via the OMS protocol. This software also allows storage and recall of Trak 2 parameters, and any operating system updates can be downloaded to the machine. However, at this point I have to admit to being entirely PC‑based, so I wasn't able to try this out.

Connections & Control

The mic preamp section contains all the facilities you might reasonably expect. Phantom power is switched independently on each channel, and with a 'Mic Protect' mode that turns phantom power off automatically whenever a mic is disconnected from the unit. This is intended to afford protection to mics that don't require phantom, or which can be damaged by it. The remaining preamp features include polarity reversal, a 20dB pad, high‑pass filtering (at 40Hz or 90Hz) and variable gain up to a massive 90dB! The step size for the gain control can be set between 0.5 and 4dB, the default being 1dB. A Channel Link facility synchronises setting changes between the two mic preamps and the mute ramps up and down to avoid clicks.

Apogee Trak 2In addition to the rear‑panel XLR mic inputs (which will also accept line levels if required), there is a pair of front‑panel Aux combi jack/XLR inputs, the jack socket being optimised for high‑impedance guitar pickups. Balanced line‑level send outputs are provided via two more XLRs on the rear panel. Under normal circumstances the signals reaching these send outputs are routed internally through to the input of the A‑D converter. However, by selecting the Insert mode (indicated by the front‑panel Ins LED), a separate pair of rear‑panel Line Input XLRs are routed to the A‑D converter instead. These line inputs can be configured in the relevant menu page for either +4dBu or ‑10dBV levels, and allow the mic preamp to be used independently of the converter, or some external compression or EQ to be applied to the mic signal prior to conversion, using the send outputs and line inputs as insert send and return.

The converter technology is derived from that used in the PSX100 and Rosetta, which I reviewed back in SOS November 1999. Both standard and doubled sample rates are supported, to 24‑bit resolution. The A‑D output is presented via one XLR connector, although the signal is software controlled for either professional (AES‑EBU) or consumer (S/PDIF) data formats, and internal jumpers configure the electrical format (impedance and voltage levels). This digital output supports single‑wire operation for doubled sample rates.

In addition to this main digital output, the two AMBus sockets can accommodate various optional bi‑directional eight‑channel digital interface cards. The eight digital outputs from each AMBus card can be assigned from any of the two internal A‑D signals and (potentially) sixteen digital inputs, through an internal router. These outputs can be bit reduced with UV22HR on a fully independent basis, although the resolution (16‑ or 20‑bit) and either the 'normal' or 'low‑level' mode are set globally. The low‑level mode is intended for use when the signal may end up passing through the UV22HR process more than once.

Although the unit contains a very accurate internal crystal clock, word‑clock I/O is provided on BNCs adjacent to the main digital output, and a video‑sync board may be installed if required to enable synchronisation to an external video reference, (connected via the word‑clock input socket). The unit can also be synchronised to one of the two AMBus interface cards. A 15‑pin D‑Sub connector forms a serial communications port, and a special lead supplied with the unit provides MIDI in, out and thru connections via this port.

The optional two‑channel D‑A converter uses XLRs for its output connections, but the eight‑channel version employs a D‑Sub connector conforming to the ubiquitous Tascam wiring standard. With the two‑channel D‑A installed, pairs of digital inputs (or the A‑D signals) can be selected for D‑A conversion. With the eight‑channel version installed, eight digital inputs can be monitored simultaneously, although any pair can also be substituted for the A‑D inputs, if required.

On The Menu Tonight...

When the system powers up, the LCD shows a status graphic, detailing the functional blocks of each channel of the mic preamp, A‑D and output routing. Above the main block diagram you can access submenus to configure advanced preamp functions, line input, A‑D and routing, while below the graphic are further panels to access the global setup menu, mute functions and clock reference (the current sample rate, reference and status also being shown). Using the cursor keys, any of these graphical boxes can be highlighted, whereupon pressing or rotating the encoder wheel will either open a submenu or change its current value or status, as appropriate.

There are currently sixteen parameter pages accessible from the global setup menu. They are largely self‑explanatory and easy to use, although there are some interesting points worth noting. In the clocking menu, for instance, internal sample rates can be selected from 44.1, 48, 88.2 or 96kHz, and the word‑clock output can be set for normal, x2 or x256 (Digidesign Super Clock).

The mic preamp menu provides additional functions not available on the status display, including input pads, phantom power, and 'Gain Ride Mode'. The Trak 2 employs internal relays to set the gain in ranges, thereby optimising the noise and distortion performance for any given signal level. However, this means that there is sometimes a brief mute or click when switching across ranges. In situations where it may be desirable to continually adjust the gain, perhaps during vocal tracking for example, this is unacceptable, so Apogee have provided the GRM mode, which fixes the analogue gain structure at its current setting, and adjusts the gain in the digital domain instead.

The A‑D menu allows the digital headroom to be established by setting the equivalence between +4dBu or ‑10dBV analogue input levels and a digital reference from ‑10 to ‑20dBFS. There is also an automatic calibration facility where the machine will align itself to a calibration tone at its input. The D‑A submenu provides similar facilities for automatic output level alignment.

The ASP menu controls the 'analogue signal processing', meaning the Soft Limit and Soft Saturate functions. The Soft Limit facility is calibrated in terms of how much 'extra' headroom can be expected, from 2dB to 10dB, followed by the witty 'more' and 'oh man!' levels. Similarly, the Soft Saturate mode provides nine degrees of 'warmth', four of 'limit', the original AD500 characteristic, then five degrees of 'crush'. Four further saturation levels are called 'raiatone', 'van der fuzz', 'distortobob' and 'sqrwavdave'. The Soft Saturate system works by accentuating the even‑order harmonics, and also by compressing the negative half of the signal waveform more than the positive half — a characteristic of many valve circuits.

The handbook talks about being able to adjust the threshold for the onset of saturation, but I was unable to locate this facility. Since the review model flash software was the current version 1.77, I presume this is an error of the handbook rather than a fault in the machine. However, I did discover a small software bug — rotating the shaft encoder quickly when cycling through the Soft Saturate options often resulted in a spurious number being displayed, rather than the appropriate Soft Saturate mode, although this didn't cause any practical problems. Having brought up the subject of things not being entirely perfect, I would like to mention the absence of a headphone volume control on the front panel. The level has to be set in one of the submenus and, although you can set up one of the user buttons to access the relevant page, a knob would have been a lot more practical.

On The Job

Using the Trak 2 is a mix of joy and frustration. Overall, it is very easy to use and works well, with a very neutral, quiet mic preamp, and high‑resolution converters. However, the menu‑driven interface does require a great deal of button pressing when setting the unit up for the first time, and the stereo linking facility only applies to the mic preamp settings and doesn't extend to the signal processing or line‑selection functions. I can see why Apogee have chosen to isolate the mic preamp facilities from the rest of the machine, but would have thought a second stereo link switch would have been useful. For example, trying to arrive at the optimum Soft Limit setting when mastering a stereo source is rather tedious, as each channel has to be adjusted separately.

Although there are no published specifications for the Trak 2 in terms of noise performance and so forth, it certainly sounds very quiet and clean, even with substantial amounts of gain. In fact, with 90dB of gain on offer, the Trak 2 can accommodate any microphone in virtually any situation. The high‑impedance input works well with a range of acoustic and electric guitar pickups too, and there is plenty of sensitivity for any source. The Soft Limit function is remarkably effective at trapping transient signals, and the Soft Saturate can be used to enhance the signal with everything from a very subtle warming through to a fairly grungy edge — something for every taste and source.

One word of warning — if the automatic A‑D calibration is activated without a suitable reference‑level signal available at the line inputs, the machine will align itself incorrectly and, as a result, the A‑Ds may well appear to be appallingly noisy and distorted. I made this mistake myself, but, after repeating the calibration with a proper test tone on the line input and then recalibrating the converters, I was able to obtain results which were indistinguishable from my own reference Apogee PSX100 system.

The Trak 2 is a big and fairly heavy unit despite being only 1U high. It extends a considerable 360mm or so behind the rack ears and I would suggest some rear support in the rack would be a good idea! The handbook recommends leaving a half‑rack gap above and below the machine for cooling, which makes sense as I found that it can get pretty warm after a full day's work. This is despite a large area of (purple) heat sink on the left‑hand side and an internal forced‑air cooling fan which is, thankfully, extremely quiet.

Overall, I am very impressed with the Trak 2 and I can overlook the occasional software bug and the menu‑driven operating system. By allowing the owner to specify much of the machine's functionality with the optional stereo or eight‑channel D‑A cards, eight AMBus interface cards, and the video‑sync option, the relatively high UK price can be justified by spending money precisely where it is needed. This is a unit which really can claim to be all things to all people, and if you are seeking a very high quality front‑end for a high‑spec digital system, this is where you should start looking.

AMBus I/O Options

Apogee Trak 2The three most obvious AMBus interfaces are probably the ADAT8, TDIF8 and AES I/O cards, all providing eight digital inputs and eight digital outputs — in Alesis ADAT, Tascam TDIF and AES‑EBU formats respectively. The ADAT card is fitted with the familiar Toslink optical connectors, while the other two employ D‑Sub connectors. I got to check out the ADAT8 AMBus card, and it performed entirely as expected, configuration switches being used to set up bit‑splitting modes (to allow 24‑bit data to be recorded on 16‑bit machines) in much the same way as the equivalent facility in the PSX100.

There are currently also four other interface cards and more are planned for the future. Three of these cards are pretty specialist, but extend the appeal of the Trak 2 into areas not previously addressed in such a direct way. The first card of this group is an SDIF interface, designed to link with Sony digital multitracks or 1630 CD‑mastering machines. A FiberDX card provides a high‑quality optical interface which caters for long‑distance fibre‑optical connections (up to 5km, apparently). Finally, the Digi8+ card provides a full eight‑channel bi‑directional interface which integrates fully with any Pro Tools system, removing the need for Digidesign's own interfaces.

Pros

  • Very clean mic preamp.
  • Mic and high-impedance guitar inputs on front panel.
  • Soft Limit and Soft Saturate useful and effective.
  • Apogee converters.
  • Useful modularity and configuration options.

Cons

  • No front-panel headphone volume control.
  • Lots of button-pushing when setting up.
  • No stereo linking of conversion and signal-processing parameters.
  • A price in accordance with a seriously professional piece of kit.

Summary

A high-quality front-end for any professional DAW or other digital recording environment. Excellent flexibility in both set up and customisation through optional interface modules. Useful as independent or integrated analogue preamp, A-D and D-A stages.

information

Trak 2 £3107.88. Optional D-A conversion cards: two-channel £411.25; eight-channel £934.13. Optional AMBus cards: ADAT8 £411.25; TDIF8 £411.25; AES I/O £581.63; FiberDX £411.25; SDIF £581.63; Digi8+ £464.13. Prices include VAT.

www.apogeedigital.com

test spec

  • Apogee Trak 2 OS v1.77
Published January 2002