Back in 2004, Mackie introduced the original Big Knob, the first affordable monitor/headphone bus controller for DAW-based studios. Essentially, Mackie took the best elements of an analog console monitor section and added some goodies like multiple recorder outputs and a phono preamp, all in a solidly-built, budget-priced package. Two years ago, they evolved the concept into a three-product line by offering varying degrees of monitor, playback, and recording control/switching. In this review, we'll look at the simpler two of the three Big Knobs, the Passive and Studio models. The Studio+ (not reviewed here) contains all the features of the Studio and more, so make sure to check out Mackie's well-designed website and read the downloadable user manuals before making a purchase decision.
The Mackie Big Knob Passive is a simple device: a good quality potentiometer, some resistors, some capacitors to snub RFI, and some 1/4-inch TRS connectors – all of this in a solid, all-metal case for about $70. Its purpose is to sit between two pieces of studio equipment such as DAWs, mixers, flash recorders, CD players, tape machines, etc., and two pairs of powered monitor speakers (or power amps driving passive monitors). Situated there, it controls input and output sources and destinations, plus monitor volume level via the large metal knob and potentiometer.
The Big Knob Passive features a pair of inputs (A and B) and a pair of outputs (also A and B). Input B allows for 1/4-inch or 1/8-inch connection. The 1/4-inch inputs and outputs can be balanced or unbalanced. There may be impedance and headroom issues mixing balanced sources and unbalanced destinations, and vice-versa, but this setup should work with most modern transformer-less gear.
The premise of passive monitor control is simple: if you insert only a volume-level control, you aren't inserting active electronics, and possible distortion, noise, and phase shift, or cancellation. As far as I could hear, the Big Knob Passive imparts zero color or flavor on the sound – it simply passes signals with a non-scratchy pot and some non-noisy resistors in the path. It seems to have a noise floor of zero and seems to have no effect on distortion or headroom between balanced sources and destinations.
The volume pot seems to be linear, not audio-taper, which is useful for studio applications. It is not a real-deal impedance-matched attenuator, so there are no detent points, and indeed no marked scale on the case. Thus, it's not easy to set up recallable points along its smooth circular travel – I suppose one could use bits of console tape to mark important points along the way? There also aren't individual trimmers on the input or output connections, so you are relying on the accuracy of the pot and resistors to maintain channel-to-channel matched levels. And, when switching between input A and B, if the devices' output levels aren't matched, you're going to have to roll out some console marking tape and do some measuring. But, that said, for $70 the Passive is well built and does its job as intended.
The Big Knob Studio is not just a source/monitor controller. It is also a 2-in/2-out USB 2 digital interface. And, there's a switch on the back that selects what the USB input sends to the computer. Switched one way, it's input channels 1 and 2 via the built-in Onyx mic preamps; the other way, it's the same output as selected for the monitors and the analog "2-Track" recorder output on the back panel. The computer's output is selectable on the front panel, and yes, you can cause a feedback loop by selecting it as the output while selecting "2-Track" as the input. The same would be true if you plugged an external tape recorder into inputs 3 and 4 and routed the "2-Track" analog outputs to its inputs and tried to record from the Big Knob while outputs 3 and 4 are selected as the monitor outputs. Simply put: the Big Knob Studio (like the original Big Knob) is not idiot-proof, so make sure your recorder is not selected as the source and destination.
The Big Knob Studio includes two balanced outputs for monitors or monitor amps, plus the aforementioned "2-Track" output for a recorder (level not effected by the monitor-volume control). Both the "2-Track" output and the inputs for Source 3/4 can be switched for +4 dB pro level or -10 dB prosumer level. Unlike the original Big Knob, there is not a trimmer for each input and output on the back panel.
Source inputs 1/2, which run through the Onyx preamps, have level trimmers on the front panel and can accept XLR mic inputs, 1/4-inch TRS line inputs, or 1/4-inch TS instrument inputs. There is also 48V phantom power (switchable on the front panel – make sure to keep it OFF except to phantom-power appropriate microphones). A useful "Stereo Pan" switch works like this: switched in, channel 1 feeds the left output and channel 2 feeds the right output; switched out, inputs 1 and 2 are mixed together in mono, feeding both channels and the mix is controlled by their trimmer level knobs. Source 3/4 can also be from a 1/8-inch connector on the front panel. When the 1/8-inch is plugged in, it takes precedence over the 1/4-inch connectors on the rear panel.
Oh yeah – there are also two headphone outputs on the front panel, fed from separate high-power amps, each with their own volume control. Bottom line, this is VERY flexible, like the original Big Knob. And, like I said, the Studio+ is even more flexible, including two more line inputs, a 2x4 USB interface, and a dedicated headphone feed for the musicians.
Now here's the rub: to my ears, like the original Big Knob, the Big Knob Studio (and, presumably, the Studio+), do impart a "sound" on everything. I will describe it as a hazing up of things – a slight fuzzing of the stereophony, and a little bit less width and depth. I also hear a little phase-shift going on in the very low end. It's nothing terrible, and not as noticeable as for instance running signal through a typical piece of hi-fi gear – but it's audible, to my ears, that output isn't exactly input. The USB interface is good but not great (in my opinion), but it's a hell of a lot better than what cost decent coin back when the original Big Knob debuted. I suspect that the underlying problem here is too many op-amps in the signal paths and which op-amps were used, plus all other parts in the system that were spec'd to stay within a very affordable price point. It's definitely not cheapo junk gear, but I wouldn't classify it as mastering quality. I do think the price would need to be a good bit higher for there to be a noticeably more transparent sound. In other words, Mackie did as well as possible for this, and even higher, for the given price points.
So, who's the ideal buyer for the Big Knob Studio? Definitely a recordist or musician starting out and working under budget constraints. Combine this thing with a decent low-end laptop and you've got a complete studio including very good mic preamps with the ability to be quite creative both inside and outside of the box. The sound quality of every aspect of the Big Knob Studio smokes earlier-era amateur studio gear – especially the ADC/DAC USB interfaces. By the time you've stepped up to really good monitors – and a really good monitoring environment, you'll be out of the Studio or Studio+ league. But that Big Knob Passive can fit well into a higher-fidelity environment.
Another obvious place for a Big Knob Studio would be a purpose-build web-cast/podcast or smaller-scale archival transfer studio. Unless you're working with master-quality audio sources, everything about the Studio or Studio+ is fine for those jobs. The affordability and flexibility are very appealing. In the world of a web-cast/podcast studio, that money saved could be spent on better room treatment and a better microphone. In the world of a small-scale transfer studio, the money saved could be spent on the best possible analog playback chain. Either scenario will get you much more sonic bang for the buck than scaling way up on digital interfaces or monitor controllers.
So, Mackie has scored again. For what these units cost, they are category killers! Until you get to the major leagues, they will suit your sonic needs just fine. The Big Knob Passive is so useful and priced so modestly, it belongs in most studios, connected to the patchbay.