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Drawmer Masterflow DC2476

Mastering Processor By Paul White
Published October 1999

Drawmer Masterflow DC2476

Drawmer are the latest hi‑tech analogue equipment manufacturers to enter the digital world of all‑in‑one mastering solutions. Paul White finds out how well they've pulled it off.

Drawmer's Masterflow DC2476 purports to be a one‑box solution to dynamic processing and equalisation needs, aimed primarily at stereo mastering applications, though there's no reason not to use it for routine recording and mixing applications. In this respect, it's clearly designed to compete directly with products such as the TC Electronic Finalizer and the Dbx Quantum. Unlike previous Drawmer processors, the DC2476 is entirely digital — the fruit of many years of behind‑the‑scenes digital R&D at Drawmer.

These days, you don't get taken seriously unless your digital processor can work at up to 24 bits at 96kHz, and even though few people actually use 96kHz (or 24 bits, for that matter), Drawmer were undoubtedly wise to include this facility. For those who have access to source material at greater than the current consumer delivery resolution of 16 bits, the unit also includes a choice of four noise‑shaped dithering options, allowing bit reduction while maintaining low‑level resolution. The 1U processor offers balanced analogue I/O on XLRs plus digital I/O on both AES‑EBU and S/PDIF as standard, along with word clock input and output. There's a full set of MIDI In, Out and Thru connectors for remote patch changing or data dumping, and every user parameter can also be adjusted using MIDI controller data (from version 1.03 onwards). The model reviewed was pre‑MIDI so none of these functions could be checked, though Drawmer anticipate version 1.03 being available around the time you read this review. Mixer maps are also being created for popular MIDI sequencers.

It's obvious from first glance that the look of this unit signals a radical departure from traditional Drawmer styling, though the trademark yellow and black motif is retained in the buttons. The cursor arrow keys are actually all one piece — the disc upon which the arrows are printed pivots about its centre. Other than the cursor control, there are only nine other buttons, one of which is a bypass button, plus a cone‑shaped Adjust knob with integral push switch. A mains switch is to be found on the back panel, which will obviously be difficult to access if the unit is rackmounted.

The backlit LCD is about the same size as the one used by TC in their Finalizer and everything is displayed very clearly. The designers have taken the opportunity to use the display for presenting non‑text information, such as dynamic and EQ curves, additional metering and so on. The display is arranged in pages with one or more pages for each function, and every window shows the audio chain at the top of the display, with the currently selected processing block highlighted. The editing system is very logical and the manual includes pictures of all the screens plus block diagrams.

Masterflow DC2476's rear panel exudes professionalism with its pro XLR I/O.Masterflow DC2476's rear panel exudes professionalism with its pro XLR I/O.

What Does It Do?

Like the TC Finalizer and the new Dbx Quantum, some of the processes within the DC2476 involve splitting the audio into several frequency bands, in this case three; Multi‑band dynamic processing is commonly used in mastering, as it allows processing to be applied to one part of the spectrum without adversely affecting other parts. For example, a loud bass drum will cause a conventional full‑band compressor to bring down the level of the whole signal, while a split‑band compressor can control just the bass end, leaving the mid and high end essentially unchanged. All the 2476's processing blocks are chained in a fixed order, though individual blocks may be bypassed if not required. Blocks may also be soloed to aid setting up.

Before the processing chain proper comes the input section, where it's possible to trim the input level and to phase‑reverse each channel independently — useful if you're presented with a master tape on which one channel has been inadvertently phase‑inverted! Also within the input window is a kind of storage scope display that shows a section of the input waveforms (both left and right) over a period of several seconds, the actual sweep time being user adjustable. This tells you something about the dynamics of the input signal, but is too small to convey much meaningful information.

Processing starts with a stage of dynamic equalisation, which also includes a traditional full‑band compressor that can apply positive or negative compression, so it's really a combined compressor and expander. It is interesting that Drawmer have decided to include a full‑band compressor as well as a multi‑band compressor in acknowledgement of the fact that it's sometimes useful to apply full‑band compression, especially before overall EQ. The subjective result is quite different to compressing after EQ or using multi‑band compression.

Multi‑band dynamic processing is commonly used in mastering, as it allows processing to be applied to one part of the spectrum without adversely affecting other parts.

The dynamic equaliser applies EQ boost or cut related to signal level — very low‑level signals are left alone, so as not to bring up noise in quiet sections. A floating threshold system is used where the threshold is related to the full‑band signal level, then referenced to the level of the frequency band to be dynamically equalised. It might sound complicated, but the outcome is that the dynamic boost/cut works over quite a wide dynamic range, rather than just on signals exceeding a fixed threshold. Dynamic EQ boost is useful for emphasising sound sources such as kick drums without affecting the signal between beats, while cut is useful for de‑essing or de‑popping, depending on where the EQ frequency is set. A 'Filter' listen mode enables the user to hear the effect of the filter to aid setting up. The filter itself is fully parametric.

One notable departure from tradition is the use of something Drawmer call 'bootstrap control'. Normally, a compressor reduces the level of peak signals, leaving you to restore the level via the make‑up gain control. By contrast, the bootstrap system, which is used in both the full‑band and three‑band compressor blocks, appears to leave the louder signals where they are and instead increases the level of the quieter signals, so you're not having to constantly tweak the make‑up gain controls.

Apparently Drawmer's EQ algorithm design is different to that used by most digital designers, and might better be described as modelling the components and filters that go to make up an analogue equaliser, rather than trying to come up with a digital means of calculating the overall filter response. Whatever the technicalities, the sound turns out to be surprisingly musical and analogue‑like. There are five bands in all, each of which is fully parametric and with a choice of high‑pass and low‑pass modes as well as band‑pass. The cut/boost range is 18dB.

After the equaliser section, the audio splits into three bands with user‑adjustable crossover points — the crossover page is accessible from within the menus of any of the multi‑band processors. The signal is then sent through a three‑band expander, a three‑band compressor, a three‑band limiter (which includes a three‑band stereo width control), and a three‑band simulated tube stage. Having a three‑band stereo‑width control is very useful for those people still mastering for vinyl, as it allows the low band (bass frequencies) to be mixed with less stereo spread, or even in mono, to help avoid cutting problems. Alternatively, it allows some interesting stereo width expansion tricks to be set up, as each band can be adjusted beyond 100 percent.

Both the compressor and expander have threshold, ratio, attack and release parameters displayed both numerically and graphically, though the time constants are automatically optimised by Drawmer's 'programme‑adaptive' system. The expander also has a range control, while the compressor stage includes variable gain. Adjustments may be made separately to all three audio bands, or they can be adjusted together.

Directly following the compressor, but preceding the Tube Drive section is the Limiter, which has no controls other than a release time for each band. The threshold is fixed at just below digital clipping. Sharing this page is the three‑band stereo width adjustment, again with a nice graphical display that lets you know exactly what's going on.

Finally comes the Tube Drive block, the characteristics of which are modelled on those of a triode valve. Three valve icons appear in the window to act as 'amount' meters, each of which has a separate drive value. A solid vertical bar in the centre of each valve icon shows the drive amount. The output section includes separate level controls for the three frequency bands directly prior to their recombination, after which comes another full‑band limiter (part of the automatic gain‑management system described in the box on page 62) to prevent overload that might otherwise be caused by adding three signals together. Crossover artifacts can also cause clipping, so a full‑band limiter here is pretty much essential.

Also sharing the output section is an auto‑fade system triggered by pressing the Adjust knob and adjustable up to 60 seconds. The output bit depth and the dither option to be used must be changed in the Global menu, though the shape of the fade curves may be selected here. Perhaps the only trick missed by Drawmer is sample‑rate conversion — the DC2476 does not have this facility, but then most software‑based editing and mastering systems can handle sample‑rate conversion if required.

Getting Around

There are three main operational modes, selected by dedicated buttons: Patch, Effects or Global. Patch is used for loading or saving patches to either the internal memories or an optional memory card, while Global is used to access system setup functions. Most of the time, the unit will be in Effects mode, where the individual effects blocks may be switched on and off or adjusted.

As mentioned, each processing function is configured as one block in a series‑connected chain (except for DQ, which combines dynamic EQ and full‑band compression in a single block). The chain comprises six blocks in addition to the Input and Output sections, which are accessed and edited in the same way as the effects blocks. The Chain/Parameter button switches between Chain Mode (C), for moving the cursor along the chain of processing blocks, and Parameter mode (P) where the navigation controls are used to select and change the parameters within these blocks. A 'C' or 'P' is displayed in the top left corner of the LCD to show whether the unit is currently in Chain or Parameter mode, and most blocks have only one or two pages associated with them. In Chain mode, the Left/Right cursor buttons are used to select the effect block to be edited, after which the button may be pressed to shift into Parameter mode. If an effect block has more than one screen of parameters, you can step through the pages using the Up/Down cursors.

The navigational controls are mostly conventional and intuitive — four‑way cursor arrows and a data wheel‑style Adjust knob — though the Adjust knob incorporates a push switch that is often used to move within a screen to select between things like equaliser Q, frequency or gain. It also serves as an Enter button in some situations. LED bar‑graph meters on the front panel monitor the input and output signal levels, including the main limiter activity, while three further smaller meters show the amount of compressor gain reduction in each of the three frequency bands. A collection of six coloured status LEDs to the right of the front panel show whether the current patch has been edited in any way, MIDI activity, auto Fader status, external clock and whether a high (96 or 88.2kHz) or normal (48, 44.1 or 32kHz) sampling rate is being used.

Dedicated buttons are provided for Compare, FX Bypass, FX Solo and Help. FX Solo and FX Bypass relate to individual blocks while Compare provides a means of switching back and forth between the recalled patch and its edited version. Help brings up context‑sensitive help relating to the current screen, the messages remaining visible until the Help button is released.