Sound on Sound Review: Dangerous Music D-Box

Dangerous Music are a company who thrive on providing neat solutions to typical studio work flow problems, with audio quality always at the top of the design priorities list. One of their latest offerings is a combined monitor controller and analogue summing-bus system — essentially merging the key elements of their bespoke Monitor ST and 2-Bus LT units into one convenient product. It is a neat and compact solution that has been designed to suit a specific sub-section of the relatively large home-studio market. The monitoring portion of the D-Box includes facilities to drive two sets of stereo monitors, has talkback and cue headphone feeds for performers, built-in D-A conversion for one of two digital sources and an external analogue input. On top of that,there’s a separate eight-input summing section with monitoring of its output. The separate facilities — at this quality level — would ordinarily cost significantly more than the D-Box, which manages to combine them in a useful way to meet the needs of many home studios looking to maximise the quality of mixdowns and monitoring.

The D-Box is a 1U rackmounting device, and its front panel is well laid out with logical control groupings and clear legends. It isn’t necessary to read the manual to know how to use the product, but some additional insights can be gleaned from a quick perusal, and the configuration mods aren’t entirely obvious without checking the manual first. Working through the front-panel controls, to the left is a pair of quarter-inch headphone output sockets, each with independent level control. However, both outputs are always fed with whatever’s being auditioned on the monitors — which is probably the biggest limitation to the unit’s flexibility and suitability. The headphone amps are very powerful, with plenty of headroom and low noise, and I doubt anyone will be disappointed with the level that can be generated in normal headphones, to the point that I’d warn against turning the level up fully for fear of damaging your hearing.

Next is a built-in talkback mic with an associated gain control, which enables a comfortable level to be set for the feed into the two cue headphone outputs, both of which receive the same talkback signal. In the centre of the panel are seven square, illuminated push-buttons. The first button activates the talkback mic, lighting red when active, the second switches the monitoring to mono (also red), and the third selects the alternative monitoring speakers (red again). These last two buttons are also used to access the machine’s configuration mode, and I’ll come back to that. The buttons all have automatic momentary/latched operation, in that if a button is pressed and released, the corresponding function will latch on, with another press and release needed to unlatch it. Alternatively, if the button is pressed and held the function becomes momentary and is cancelled as soon as the button is released. This form of operation is increasingly common and very intuitive, but there are obvious dangers when associated with the talkback button. Fortunately a remote-switch option allows talkback operation with a momentary action, and that might be a safer option to use!

The other four buttons are monitoring source selectors, with the first two accessing analogue inputs (the internal summing bus and a rear-panel input), illuminating green when active. The second pair access the two rear-panel digital inputs (nominally labelled DAW and CD), and illuminate yellow when active. Sources are normally selected exclusively, so that selecting one cancels the previous source, but one of the configuration options allows for a mixed selection to be formed, with multiple sources being selected or deselected as required. Only one digital source can be selected at a time, however, as there is only one D-A converter, so the selected digital source can be auditioned in a mix with the analogue and sum bus inputs, if required.

Continuing along the front panel, there’s an overall level trim control for the summing bus, which allows the output to be attenuated from unity gain to -12dB, with a mid position of about -6dB being deemed normal. LEDs indicate the presence of signals in each of the eight summing-bus inputs. The first six summing-bus inputs are configured as three stereo pairs routed directly to the mix bus, with the odd numbers feeding the left output and the even numbers feeding the right. Inputs seven and eight can be positioned within the stereo image via a pair of pan pots on the front panel — although these can also be cranked hard left and right to make a fourth stereo pair if you just want to mix four stereo stems, for example. Finally, at the extreme right of the front panel there’s a large rotary monitor volume control for the main monitoring level.

Ins & Outs
Moving around to the rear panel, the first connector is a quarter-inch TRS jack socket for hooking up a remote switch to operate the talkback mic, and this is active when the tip and ring are shorted together. A latching or momentary switch could be used, but I’d recommend the latter — either as a hand switch or a footswitch. Either way, the remote control facility is a useful one to have. Next is a pair of female XLR sockets for the primary stereo balanced analogue monitoring input (labelled ‘Analog’). This is factory set for a standard +4dBu input signal, but can be configured to accommodate semi-pro devices operating at a nominal -10dBV. The eight balanced summing-bus inputs are connected via a 25-way D-sub socket wired to the ubiquitous Tascam standard (input impedance is a reasonable 25kΩ).

The D-Box is powered from an external mains supply unit, which connects to the rack box via a five-way DIN socket mounted just to the right of the summing bus D-sub connector, and the unit consumes a modest 25W. Next is a pair of three-pin XLR sockets for two digital inputs (labelled DAW and CD). AES-3 or S/PDIF signals are accepted with sample rates from 32 to 96kHz on either input, and the manual includes wiring diagrams illustrating two alternative ways of connecting coaxial S/PDIF outputs to the XLR input socket. The remaining connectors are all male XLRs and provide the balanced line-level analogue outputs at nominal +4dBu levels. The first two are the outputs of the stereo summing-bus section, followed by a pair for the main monitors and a second pair for the alternative speakers. Again, everything is clearly labelled and interfacing the unit is very obvious and straightforward — aided by some helpful hook-up illustrations in the manual.

As mentioned earlier, the D-Box has a couple of user-configurable options, which are accessed by pressing the ‘Mono’ and ‘Alt Spkr’ buttons simultaneously. With the two buttons flashing to indicate that the setup mode is in action, the monitoring mode can be switched between exclusive source selection and additive mixing, and the analogue input’s sensitivity can be switched between +4dBu or -10dBV. This setup mode is a simple and reliable way of configuring the unit, and the options add usefully to its versatility. Interestingly, a little lateral thought and some replugging would allow the D-Box to be used to mix up to 12 channels instead of just eight, should the need arise. By configuring the monitoring section for source mixing, and then selecting the summing bus, analogue input and one of the digital inputs, you could mix the eight summing-bus inputs with the stereo analogue input and a converted stereo digital input — 12 channels mixed together at the monitor output sockets!

Taking off the lid reveals the usual high standards of build quality that we’ve come to expect of Dangerous Music products. The mix-bus circuitry is neatly partitioned from the monitoring circuitry to ensure minimal crosstalk, and for the digital inputs I spied an Analog Devices AD1854 D-A converter chip allied to a Cirrus 8416 digital receiver. I’m told the summing section is virtually identical to that of the 2-Bus LT (but with only eight inputs instead of 16, of course) and the technical specifications are equally as good. The frequency response is quoted as extending between 1Hz and 100kHz (within 0.1dB, which is flatter than the 2-Bus LT), with THD + Noise better than 0.003 percent, intermodulation distortion less than 0.004 percent and noise below -89dBu. It can also cope with very hot input signals up to +27dBu, which is useful. The monitor section boasts very similar specifications, as does the D-A converter section, so each of the separate elements within the D-Box are well matched, with no obvious weak points in the chain.

All of the I/O is tidily located on the rear of the D-box, and include a space-saving D-sub connector for the summing-bus inputs. All of the I/O is tidily located on the rear of the D-box, and include a space-saving D-sub connector for the summing-bus inputs.

The overall sound of the D-Box is classy: it sounds as expensive as it is, with all the virtues of well-engineered analogue circuit design. It gives a clear and open sound, with a solid bottom end and good, stable spatial imaging. The D-A converter is also very good, possibly tending towards a hint of warmth rather than clinical sterility, and I detected no noticeable sense of fatigue even after extended listening, which is always a good sign. In general, the monitoring section performed every bit as well as you’d expect of a monitoring controller at this price — even ignoring the ‘free’ inclusion of a summing mixer. Switching between sources was click-free, and even changing between digital sources with different sample rates provided only brief mutes. The volume control stereo-tracking was very good, particularly over the most-used middle portion of the range, and the inclusion of a mono button was very useful. There are no gain trims to balance up the levels of the main and alternative monitors, but that can usually be performed easily enough on the input sensitivity controls of powered monitors or amps. Everything feels solid and reliable, and the buttons and knobs all give the impression that they’ll provide long service.

The two headphone amps are unusually powerful — almost worryingly so — but are very quiet and provide a solid and accurate sound. However, I was disappointed that the headphone outputs can only carry the same signal as the main monitoring selection. I think this is very limiting, and to the extent that the D-Box simply won’t be suitable for a lot of potential users. It would be acceptable for someone working on their own and recording their own performances, but is far too restrictive for a more professional setup. This arrangement makes it impossible to monitor a solo channel while recording, for example, without disturbing the performer’s cue mix and, equally importantly, it doesn’t allow any way of providing ‘comfort reverb’ on a vocalists headphones independently of what the engineer needs to hear. Most other monitor controllers (even relatively affordable designs like the Presonus Central Station and Mackie Big Knob) provide external cue-mix inputs specifically to address this common requirement. This seems to be a significant weakness in an otherwise excellent product.

Moving on to the eight-channel mix bus, this is clearly of very high quality, and far better than any budget mixer that I’ve heard. It provides that analogue magic that seems to help a mix gel together in a more satisfying way, and boasts loads of headroom and a very low noise floor. It may not be as technically accurate as an in-the-box mix should be, but there’s no doubting that it sounds nice, and that is reason enough to justify its inclusion. Should you eventually need additional summing inputs, the system could be expanded easily enough with a Dangerous Music 2-Bus or 2-Bus LT — or any other manufacturer’s analogue mix bus unit, for that matter. Even if you don’t need or want to use the mix bus to create your final stereo mix, it exists as a separate entity within the D-Box and can be used for other purposes. For example, a number of external keyboards or rack sound generators could be submixed through it with better quality than a budget mixer would achieve — and with the built-in monitoring facility you wouldn’t even need to fire up the computer or a separate hardware mixer to practice your chops!

The talkback facility is an oddity, and I haven’t been able to quite make up my mind about its usefulness. If the performers are in a separate room, the addition of talkback is very handy, but the restriction on the control-room monitoring sources reduces the practicality of working like that anyway. And for the performer/engineer who wouldn’t be bothered by the lack of monitoring flexibility, the talkback is superfluous. All that being said, the addition of a remote talkback switch function is a good idea, but I’d have preferred to have a talkback output instead (or, even better, as well). That would have allowed the flexibility and usefulness of the D-Box to be extended significantly with the addition of an external headphone system, providing independent selection of monitoring and cue sources, but retaining the ability to talk to the performers.

My only real concern with the design of the D-Box is in the cue-monitoring arrangements that restrict its flexibility as a monitor controller. The result is that the product will either suit a user’s needs and way of working perfectly, or it will be completely unacceptable — and that seems an enormous waste for the sake of an additional pair of external inputs to the Cue system. There can be no doubt, though, that the audio quality of the D-Box is superb, both as a monitor controller and as a summing mixer, and the combination of the two functions at this price makes for a very attractive unit.

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