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Bettermaker Mastering Limiter

Digitally Controlled Analogue Limiter
Published December 2017
By Hugh Robjohns

BettermakerMastering Limiter

With its DAW integration, colour touchscreen and harmonic generator, Bettermaker’s latest processor is much more than just a limiter.

Despite the amazing technology now available to pro-audio manufacturers, I frequently find myself disappointed at the dearth of truly innovative new products — so much of the industry seems committed to looking backwards, and happy to market homages to vintage equipment. Thankfully this isn’t the case with Bettermaker, an inspiring company which grew out of a recording studio set up in 2004. Their mission seems to be to build equipment that’s genuinely useful to fellow recording engineers, and to that end they’re more than willing to move things forward with new tools and new ways of working.

Overview

The latest member of the company’s small but interesting product portfolio is the stereo Mastering Limiter and, as with Bettermaker’s other products, it’s a digitally controlled analogue device that can also be operated remotely through a DAW plug-in. It’s housed in a substantial 2U 19-inch rackmountable chassis, with a large colour screen front and centre — from which you might already surmise that this is rather more than ‘just a limiter’. You’d be right!

At its core, the Mastering limiter is a reasonably conventional but high-performance analogue limiter, with options to operate in either stereo or Mid-Sides modes. The gain-reduction element used for the limiter is a fast-acting VCA with a fixed ratio of ∞:1 (infinity to one) and a maximum attenuation of 20dB. It’s a fixed-threshold design, so the limiting level is determined by the output level control, and the amount of gain reduction by the input level control. The attack and release are adjustable manually, but there’s also a programme-dependent automatic release mode. As everything is controlled digitally, all settings are incremental, precisely repeatable, and recallable, which is ideal for mastering applications.

So far, so ordinary... but Bettermaker go beyond a simple limiter by adding a two-stage analogue clipping section after the limiter VCA (this can be bypassed for those that prefer to use an outboard A-D for clipping purposes). In essence, the clipper takes care of any transients that slip through the limiter, guaranteeing a precisely defined absolute peak level. The relative balance of effort between the limiter and clipper is effectively controlled by adjusting the limiter’s attack time.

And still there’s more! Preceding the limiter’s VCA is a rather intriguing ‘Colour’ section, which allows harmonic distortion to be introduced for a range of tonal thickening/sweetening effects. There are two separate harmonics generators, one that produces odd harmonics, and another that creates even harmonics. Both have independent drive and level controls, which determine how rich the harmonic generation is, and at what level these harmonics are blended with the source signal. Interestingly, each section also has its own band-pass filter that determines which frequency region of the input signal is used as the source to generate the harmonics. This allows odd harmonics to be added at the low end for thickening effects, but even harmonics at the high end to give a warmer, sweeter sound. The control ranges span very subtle to in-your-face grunge, and I was very pleasantly impressed with what this section adds to the unit.

But while being able to mess around with the programme dynamics and harmonic content is all good fun, in mastering the key is knowing precisely what the signal is really doing: what the peak and RMS levels really are, what the stereo image is doing, and — at least until the loudness-wars peak-normalisation practice dies off — whether there are any intersample peaks. To that end, the fourth aspect of the Bettermaker Mastering Limiter is a very comprehensive suite of metering tools (although it’s worth noting that parts of this still appear to be under development at the time of writing).

The two large chips in the PCB’s bottom-right quadrant are the control micro-controllers. The VCAs, slightly above and left of centre, sit below the I/O balanced line drivers/receivers, and above these (top left corner) are the bypass relays. Most of the circuitry below the VCAs relates to the digital parameter control.The two large chips in the PCB’s bottom-right quadrant are the control micro-controllers. The VCAs, slightly above and left of centre, sit below the I/O balanced line drivers/receivers, and above these (top left corner) are the bypass relays. Most of the circuitry below the VCAs relates to the digital parameter control.Finally, while all of these facilities can be controlled directly from the front panel, with preferred settings stored and recalled as presets, it can also be operated remotely from a plug-in, which is available in VST 2, VST 3 (both 32- and 64-bit), AU, and AAX formats. Not only is this convenient for project recall, but it allows the unit to be bolted into a rack somewhere out of arm’s reach, and still be operated very precisely from the listening sweet spot. Even more usefully, of course, when controlled remotely via the plug-in the unit’s functions can also be automated as part of a DAW project, further extending the creative possibilities.

Technicals

In line with Bettermaker’s core policy, the Mastering Limiter’s analogue signal path uses high-quality components throughout (THAT Corporation balanced line receivers and drivers, NE5532 op-amps, sealed relays, and so on). An internal linear power supply is configurable for 115 or 230 Volts AC operation, and everything is contained on a single large PCB, built mainly with surface-mount components. Entirely separate ground planes have been maintained across the PCB for the analogue and digital circuitry, to avoid unwanted crosstalk and interference between the two sections. The core limiter circuitry is based around THAT Corporation 4031 chips, which are high-performance Blackmer VCAs. I also noticed a lot of Analog Devices AD5263 ‘digital potentiometer’ chips providing digital parameter control.

Around the back of the unit are the stereo line I/O, a voltage selector, and the USB port that allows for DAW control.Around the back of the unit are the stereo line I/O, a voltage selector, and the USB port that allows for DAW control.

At the back of the device, two channels of balanced (nominally +4dBu) line-level audio are connected via XLRs, and the unit accepts up to +21.5dBu at the input but can provide up to +23dBu out. This is slightly surprising, as, while this is fine in the European environment, where 0dBFS = +18dBu, the American standard for digital/analogue alignment requires 0dBFS to align with +24dBu... which the Mastering Limiter can’t manage. In most situations I think this can be worked around without too much difficulty, but it strikes me as an odd design decision.

Running a suite of bench tests with an Audio Precision system, the THD+N figure came out at 0.07 percent (ref +4dBu), and the signal to noise ratio is 94dB (ref +4dBu), giving a dynamic range of about 111dB. The frequency response is ruler flat between 15Hz and 50kHz (±0.1dB limits), with -3dB points at 7Hz and something well in excess of 80kHz. Crosstalk at 10kHz is better than -80dB. The harmonic generators are very powerful, and massive amounts of distortion can be dialled in, if desired, with the even harmonics being much less obvious than the odd harmonics, of course. I found it best to keep the drive levels well down, at around 10-30 percent, and then tweak the amount level to taste.

A type-B (square) USB socket on the rear panel provides an optional link to a computer (compatible with USB 2.0 and 3.0) for the remote control plug-in and firmware updates, and mains power is connected via the ubiquitous fused IEC inlet (with a slide switch to select the operating voltage).

A very useful block diagram is included in the manual to show the signal path, since there’s a lot going on here. The input signal is split four ways with direct feeds to the metering and a summing node, while the other two go to the even- and odd-harmonic generators (each via an adjustable band-pass filter). The outputs from these two harmonic generators are recombined at the summing node so that the harmonic content can be mixed with the input signal as required before passing into the limiter section.

The limiter section comprises the VCA and soft-clipper, but these are sandwiched between a pair of Mid-Sides matrices so that this dynamics processing can be applied either to the normal stereo signal, or its Mid-Sides equivalent. Both the limiter and clipper have fixed thresholds, as previously mentioned, but the clipper threshold is set 3dB higher than the limiter’s. So more input level means more limiting and, if enabled, potentially more clipping. The idea of the clipper is primarily to catch any brief transients that slip past the limiter (which they will because of its non-zero attack time). Finally, the output from the limiter section (post M-S matrix) is routed through a hard-clipper (for the ultimate in peak level control!) to the outputs, and a split of the output signal is routed back into the metering.

Everything in the Mastering Limiter is managed through a pair of 32-bit micro-controllers, the firmware of which can be updated via the USB connection. Apparently, one of these devices is wholly responsible for the limiter’s VCA operation, while the other takes care of the user-interface, preset store/recall, USB connectivity, and the metering functions. In the course of this review, I had to update the firmware for compatibility with the latest plug-in software, and I was perplexed to find the new firmware listed with two revision numbers — v0.97 and v0.62 (released in August 2017). However, it makes sense when you realise that there are two micro-controllers doing entirely unrelated things, each with their own firmware. Upgrading the firmware is simple enough, but there are two distinct stages in the process, which might catch out the unsuspecting!

Operation

The front panel is deceptively simple, with a large colour touchscreen dominating the centre, sandwiched between two large rotary encoders. The large left encoder knob always adjusts the input level (and thus the amount of limiting), while the one on the right defaults to adjusting the output level (but is also used for setting the contribution of the harmonic generators and various other things). Other controls comprise a chunky mains on/off switch, a smaller button on the left which bypasses the unit, and two small rotary encoders on the right that normally adjust the attack and release times. These also feature push-button actions (although I couldn’t find any functions in the current firmware that employed this facility), and are velocity-sensitive to flip between coarse scrolling and fine increments.

A screenshot of the plug-in. In this example the ‘clippiter’ value is quite high, allowing the clipper stage to process fast transients. In this case the limiter is applying around 1dB of gain reduction, and the clipper section is taking off about the same.A screenshot of the plug-in. In this example the ‘clippiter’ value is quite high, allowing the clipper stage to process fast transients. In this case the limiter is applying around 1dB of gain reduction, and the clipper section is taking off about the same.On power up, the display features a horizontal bar-graph at the top (spanning -36 to +3 dBFS) for input or output levels, with numeric displays for the peak levels. A blue gain-reduction meter below covers an 8dB range, and a second short bar-graph meter shows the action of the clipper (over a 6dB range). To the right is a display of the harmonic (Colour) generator settings.

Five numeric parameter boxes below the meters provide the input level, attack time (0.1 to 250 milliseconds), release time (0.1 to 1.3 seconds), and output level, while seven virtual buttons at the bottom of the display access various setup functions such as a preferences menu, switching the main level meter between the input and output signals, and engaging the clipper. Interestingly, when the clipper is activated the attack time parameter becomes a ‘clippiter’ value showing the ratio between limiting and clipping. In essence, small numbers set a fast attack time so that the limiter does most of the work; large numbers use a slower attack time passing more transients through to the clipper. A value of 100 percent disables the VCA limiter altogether.

The middle button in the row engages the Mid-Sides matrix for the limiter/clipper section, whereupon the middle parameter box allows the Sides level to be adjusted ±8dB to alter the stereo width. Next along the row is the limiter’s Intelligent Release function (‘Irel’), which disables the manual release time parameter, controlling the release time depending on the signal content and the amount of gain reduction. Another soft button here resets the parameter values to default settings, while the last button calls up the main unit configuration menu page where, amongst other things, the Colour generator can be set up.

The odd and even harmonic generators can be switched on or off independently, and their drive levels, the centre frequencies of the band-pass filters, and the contribution amounts can all be adjusted using the P1, P2 and output knobs. Also, since adjusting the harmonic generators is likely to affect the overall signal level going into the limiter section, the input knob remains active so that the amount of limiting/clipping can be adjusted as necessary.

In the current firmware, the metering options include a spectrum analyser (labelled FFT), which can be displayed either as a 31-band RTA style, or as an FFT graph complete with a moveable frequency cursor. There’s also a K-meter display option with all three headroom modes, and four different moving-coil meter emulations (PPMs, two different styles of VU, and a digitally scaled meter). However, two of the metering modes were not fully operational at the time of writing, and these are the BS1770 loudness display, and a phase/vectorscope display.

The beta plug-in software includes an undocumented scrolling timeline display, which shows the input and output levels, gain reduction and clipper action.The beta plug-in software includes an undocumented scrolling timeline display, which shows the input and output levels, gain reduction and clipper action.Other functions accessed through the configuration menu include preset memory load/save (up to 399 unit settings can be stored, and a QWERTY keyboard appears on the display for titling each preset), display brightness, calibration of the unit’s metering, firmware revision details, serial number, and so on. Being able to calibrate the unit’s metering to exactly to match a DAW’s meters (taking into account any interface converter sensitivity variances) is a very sensible idea and the process is very straightforward. The only significant omission I can think of is that there’s no display contrast/azimuth control, and that’s a shame because the screen is quite difficult to read when viewed from above — as it might well be if the Mastering Limiter were bolted into an under-desk rack.

Plug-in

In the interests of fairness, I should state that while the hardware was the final production version, the plug-in available during the review period was a beta release rather than the final product — so some functions may have changed by the time you read this. Nevertheless, when the hardware was connected over USB the plug-in found it instantly, with parameter changes made on the hardware being reflected instantly in the plug-in, and vice versa. Oddly, I couldn’t find a way of toggling the plug-in’s level metering between input and output, although the plug-in responded to I/O meter selections made at the hardware unit. Also, none of the dedicated metering options were available on the plug-in; only the I/O level bar-graphs, gain-reduction, and clipping meters are shown.

Impressions

A screenshot of the plug-in as the limiter applies 3.5dB of limiting.A screenshot of the plug-in as the limiter applies 3.5dB of limiting.Like all of Bettermaker’s products, the Mastering Limiter looks elegant and refined, is very solidly built, and in its default mode it sounds very clean and transparent. For all of my testing, I plugged the Mastering Limiter into an analogue insert loop of my Crookwood mastering console, and compared its performance mostly against a Drawmer Masterflow DC2476 digital mastering processor, which I often use, as well a variety of plug-ins from UAD and others. In my experience, all limiters, whether analogue or digital, sound different and respond differently to the music passing through them, so making direct comparisons is often more misleading than helpful. What matters is whether a limiter can effect the appropriate dynamic control required in any given situation, and whether the various parameters allow the appropriate settings to be found quickly and easily.

The answer to these questions is an unequivocal “Yes!” for the Bettermaker Mastering Limiter. I found it very easy to dial in the required input level and attack times to exert the precise amount of peak control I required. I generally left the release time in the ‘Irel’ automatic mode which seemed to do a very good job most of the time, although sometimes I found setting the release manually achieved the effect I was looking for more readily.

Here, the M-S limiting mode has been activated, and the stereo width increased considerably. In M-S mode, most limiting is inevitably performed only on the Mid channel, as can be seen in the gain-reduction meter. The odd-harmonic Colour generator has also been enabled, with quite a hefty contribution to the mix!Here, the M-S limiting mode has been activated, and the stereo width increased considerably. In M-S mode, most limiting is inevitably performed only on the Mid channel, as can be seen in the gain-reduction meter. The odd-harmonic Colour generator has also been enabled, with quite a hefty contribution to the mix!I’m not personally a fan of peak-normalisation at all, and so using heavy limiting to push the perceived loudness up is not something that comes naturally or comfortably to my ears, and I would never intentionally clip the signal when mastering... but I do recognise that these techniques are still widely employed and often demanded so, gritting my teeth, I explored the clipping options and found that they are implemented very well in the Mastering Limiter. I know many mastering engineers like to introduce some mild clipping through their favoured A-D converters, and that option remains here, of course, but the combination of soft and hard clippers in this Mastering Limiter can certainly be used to good effect to squeeze out those last fractions of a decibel of ‘loudness’ if desired.

The ability to limit and clip signals in the Mid-Sides mode can be very handy indeed, as can the option to widen things a little — although I usually find that this is something that works best when approached in a frequency-selective way, rather than as a broadband tool.

If I had to name one feature that really impressed in this Mastering Limiter, it would undoubtedly be the Colour section. Dialling in a little saturation distortion can often work wonders on a mix, but the level of control provided here is outstanding. Being able to ‘tune’ the spectral regions that generate most of the distortion components, and adjusting how strong those components are and how much of them makes it into the mix, creates a very powerful and creative tool indeed. It’s very easy to overdo the effect, but when treated with care and respect this feature almost justifies the cost of the unit on its own — it’s that good!

The extended metering facilities are nice to have, but I suspect are of limited practical use in reality. If I need K-metering, vector-phase analysis and so on, I would much rather use the tools I already have in the computer, where I can also view them on a larger screen. However, in a wholly traditional analogue mastering setup, having these tools would be very useful.

Overall, I think Marek Walaszek and his team at Bettermaker have come up with a really interesting, powerful, and creative tool in the Mastering Limiter, and for anyone looking to invest in a very nice hardware processor to add some polish to their mixes, I can certainly recommend this one.  

Alternatives

The world of mastering limiters is a rarefied one, and most mastering dynamics processors around the price of the Bettermaker are actually compressors, rather than just limiters. I’m thinking of devices like the Maselec MLA2, the IGS Tubecore ME, and the Buzz Audio DBC-M, amongst others. However, none offer the range of precise controllability of the Bettermaker or the adjustable Colour feature, let alone the integrated remote-control plug-in option, all of which make the Mastering Limiter unique. If plug-in controlled analogue compressors appeal to you more generally, also check out the offerings of Wes Audio and Tegeler Audio.

Published December 2017