Behind The Design Of The Soundcraft DC2000 Moving Fader Console
Paul White bypasses security at Soundcraft's R&D centre, where he quizzes John Oakley and Jo Jenkins about the design of their low-cost, moving fader DC2000 Automated Mixing Console.
Most of us will be pretty familiar with the underlying concept of console automation, though few of us have actually used a fully automated console. That presented console manufacturers Soundcraft with a dilemma; if you're building a system to compete with something that already exists, you know what kind of user interface people are familiar with — but when it comes to designing an automated mixing console for the private studio market where automation is still an expensive luxury, which route do you take? In designing their brand-new DC2000 console, projected for release in July, Soundcraft decided to take the moving fader route because it offers a very visual environment in which to work and it doesn't rely on external computers for its operation or its display. But how were they able to achieve all this at the provisional asking price of around £12,000 plus VAT? (To put this in context, consoles equipped with moving faders can cost upwards of ten times this amount). I put the question to designers John Oakley and Jo Jenkins at Soundcraft's R&D HQ, where we talked about the background to the DC2000.
John Oakley: "We set off about three years ago with a view to bringing down the price of automation to a level where people could afford it. We had to set a price point and that meant going right back to basics and examining every aspect of the console to see if it could be made at a lower cost than before. We've gained so much experience over the past five years on how to do things effectively without compromising reliability, that we've been able to bring all that to the DC2000. For example, the chassis construction is very simple, but in terms of strength, it's rather like the monocoque body on a car. Once it's all bolted together, it's incredibly rigid. There's also a lot of fancy silicon and surface mount technology gone into the circuit design to make manufacture more straightforward.
"There is a problem in the concept of automation for the mass market because nobody really knows what to expect. A few people in this market sector will have worked with a VCA-based system, but one of the problems with VCA systems is that you don't get any direct visual feedback of the level setting from the fader position — you have to look at a screen or some other form of display. With a moving fader it's simple — where the fader is, the sound is.
"On the other side of the coin, some people have got used to the way VCA systems work and they have become familiar with concepts such as 'update' and 'offset'. When working on a moving fader console, these things have to be unlearned."
Automation aside, the console itself, though not a radical departure from convention, is based on existing Soundcraft circuitry and designs, some of it imported from consoles much further up the price ladder. It is available in two frame sizes, 24 or 32, the latter providing 72 inputs on mixdown via the two channel signal paths and the stereo returns. Unlike most home recording consoles, which feature in-line monitoring and split grouping, the DC2000 conforms more closely to the true in-line design. Each channel has a direct output to tape, allowing individual signals to be recorded via the shortest signal path, but for routing mixes of several channels to tape, there are eight floating group busses feeding four stereo Group Masters. Full routing is included to facilitate straightforward bouncing and the four-band EQ may be split between the Input and Monitor signal paths, as is rapidly becoming the convention. Many of the routing features have their origins in the Soundcraft Sapphyre, and like that console, the channel path is equipped with a short fader for level control rather than the more customary rotary pot. All the console inputs are balanced and outputs are ground compensated, with the exception of the insert points, and automated cuts are provided for both channel signal paths, all six aux send masters, channel sends 1 and 3, the four stereo groups and the four stereo aux returns.
John Oakley: "One of the key features is that we tried to make this console easy to use, and it can be used as a conventional console, without the automation, if necessary. The EQ is derived from our traditional '4-band with swept mids' approach, and the two halves are separately switchable between the two audio paths. In addition, the high and low controls have separately switchable roll over points to make them more effective in a split situation. In terms of the rest of the desk, its provenance is almost pure Sapphyre, especially in the way the routing works.
"As you get more into the moving fader concept, you realise that little things like fader reverse become a little difficult, and in fact the Sapphyre concept, where you always do the mix or the monitoring on the long fader at the bottom, is actually the right approach for a motorised fader desk. When you're laying down the tracks and setting up a monitor mix, you've probably got the basis of your automated mix already, so when you go to mixdown, the last thing you want is to have to swap between faders or lose your mix and start again from scratch. So, the long fader with the motor is, in effect, the one you always use to 'listen' with, and concepts such as fader reverse become irrelevant in that context.
"The short fader routes the channel signal directly to the tape out on the back of the module and the direct output is the normal mode of operation. The direct output is wired to the correspondingly-numbered tape track input. If you want to route a mix of channels to tape, the routing buttons take you via the groups, which are arranged as four stereo pairs rather than as eight individual groups. We felt the primary use for the groups was probably going to be for bouncing down tracks, and bouncing tends to be done as stereo pairs. The groups are normalled back to the tape outputs in blocks of eight, just like Sapphyre, which means you aren't forced to repatch if you want to send a group signal to a tape track higher than eight.
"If you press the Tape Source button, instead of the direct channel output, it picks up the equivalent group number and routes that to tape. The Bounce button takes the tape return signal and feeds it through the long fader and the routing matrix. There are six aux sends per channel strip and aux 1 and 3 may be linked, allowing the same effects unit to be shared between both signal paths. This is particularly valuable at mixdown, when the monitor inputs are being used as additional line inputs."
This is obviously a very nicely thought out console, even without the automation, but what really fires people's imagination is the moving fader automation. I understand that this is controlled entirely by an on-board computer using a combination of buttons and a touch sensitive LCD screen.
John Oakley: "The display is a touch sensitive LCD screen which not only allows access to the automation, but also allows specific channels to be designated as 'safe' in Solo-In-Place mode. This also addresses the problem of whether the two channel input paths should be linked for this purpose or whether they should be separate. And, because we have a screen, we can also store project titles and suchlike. There'll also be a SMPTE readout in the middle of the meter bridge on the production models.
"The data wheel adjacent to the screen may be used to scroll around the screen but may also be used as a shuttle/jog wheel if the console is used with a compatible tape machine. We're obviously looking into compatibility with the Alesis ADAT and Tascam's DA88."
Jo Jenkins: "The automation system is designed to be easy to use and to be acceptable to people who haven't used automation before. Functionally a moving fader is much easier to use because it provides a direct indication of the level setting, and the fact that this particular fader is now available has now made this practical."
"One of the problems with VCA systems is that you don't get any direct visual feedback of the level setting from the fader position. With a moving fader it's simple — where the fader is, the sound is."John Oakley
Is this a standard fader or is it customised in any way for your application?
John Oakley: "This is an Alps fader and I think we're the first people to use it. I first visited Alps in Japan around three years ago and told them that we needed a low-cost moving fader. Everything else was too expensive. We heard nothing for a long time, then they turned up with a working model. We used it and came up with a list of improvements and we've been going round that loop ever since. I think we were on about the 10th prototype before we were happy with it."
I was impressed by the mechanical ingenuity of the fader [we were told about this in considerable detail but have been asked not to reveal too much for obvious commercial reasons]. Presumably there is a problem in preventing the motors, which are conventional brush-type devices, from radiating interference onto the audio path?
John Oakley: "Rule number one; if you can hear the automation working, it isn't good enough. That's something that's applied to all our automated consoles from the 6000 to Spirit Auto."
In the case of motorised faders, that must mean you have to take enormous care over the earthing arrangements!
John Oakley: "That's one of the sensitive areas that I can't talk further about — I'll just say that we've gone to extreme lengths to ensure that the console can be built to a consistent quality using mass production techniques. Typically, it's not too hard to hand-craft one or two to be quiet, but when it comes to mass production, you can get into trouble. In the three years that it's taken us to develop the console, a lot of work went into that particular area and we've even developed a custom chip to help address the problem."
Have you had to resort to balanced mix busses in order to achieve the required degree of isolation?
John Oakley: "No, these are just conventional busses. There's a lot of ground compensation goes on, but that works pretty well." [Again, some of the measures taken were explained to us in detail, but once more we have been asked not to reveal them.]
Once the technology was there to drive the faders, how did you decide on a control system?
Jo Jenkins: "When the console is first switched on, it powers up as a conventional console with the automation disengaged. All the automation is integrated into the console — the DC2000 was designed as an automated console so it isn't a matter of taking an existing console and bolting bits on. There is an integral disk drive allowing mix data to be stored straight to disk, and the fact that everything is internal means that we aren't limited by the speed of MIDI, as is often the case with systems running from external computers.
"The console will read and write all four SMPTE time codes and MTC, and these may be set up via a simple menu system using the touch-sensitive LCD display. This only needs doing once, so having to go via the screen is acceptable. What we have done is to provide dedicated buttons for the functions that you need regularly while mixing so you don't have to worry about the touch-sensitive screen for those.
"Assume that you've laid your tracks to tape with no automation and you now want to do your first mix. Simply hit Mix On, which puts all the channels into write mode, and start the tape. We have central transport buttons which support MIDI Machine Control and also RS422. You run through the first mix, move faders, change switches, and as soon as you press Stop at the end (or if the time code stops) all channels drop into read. Each channel has local-Mode controls which allow individual faders or switches to be switched between Read and Write modes; a red LED indicates when a fader or switch is in Write mode. There are global Read and Write select switches to save having to change all the channels individually, and 'snapshots' of Read/Write settings can be stored for use when you're returning to the same scenarios time after time. You can also take static 'snapshots' of the whole console fader and switch settings, though this may not be available on the early software releases."
"The automation system is designed to be easy to use and to be acceptable to people who haven't used automation before."Jo Jenkins
I notice that there are four Control Group faders on the master section. How do these fit in?
Jo Jenkins: "One of the disadvantages of a moving fader system is that it's difficult to add in an offset to previously recorded data as you can with a VCA. There are two ways of achieving this with the DC2000. On individual channels there is an 'armed' mode which keeps the channel in Read until the fader is touched. The action of touching the fader puts that channel into Write mode, but when you let go it returns to read. This is achieved via a touch sensor coupled to the conductive fader cap. There are two things that can be set to happen when you let go of the fader: the channel can return to following the old mix data or it can be arranged so that any offset you've created in moving the fader will continue to be added to the old mix data when you let go. In other words, if you go into Write and take the vocal level up by 5dB, when you release the fader, 5dB will be added to all the old data after that point.
"Another way of adding an offset is by using the Control Groups. These are not connected to the audio path but are read directly by the computer and the data copied onto any channels assigned to them — in other words, a fader equivalent of VCA subgrouping. The assignments are indicated by status LEDs on the individual channels, and the outcome is that you add the offsets generated by the Control Group faders to the data relating to the individual channels. It is possible to push the channel faders up against the end stops if you go too far, but all that happens is the channel with the highest level stops moving while any others in the group carry on working normally."
So you could think of it as a mechanical equivalent of limiting?
Jo Jenkins: "Yes. And when you bring the offset down again, the grouped channels regain their normal relationships. The relative scaling of the gains of any channels in a group is proportional, so that whatever the fader settings, if you fade them to zero using the Group Master faders, all the individual faders will reach zero at the same time."
Did the touch-sensitive screen present you with any problems?
John Oakley: "This type of screen is used in industrial situations, so we're confident it will stand up to studio use. The surface is divided into 60 zones, which means it can also double as a QWERTY keyboard for entering text information, such as titles. You'll notice that there is no conventional QWERTY keyboard on this console."
The console has its own built-in floppy disk drive and there's also provision for an internal hard drive. Each successive mix modification is stored to disk, though you can specify how many versions you keep. For example, if you set the system to keep only ten copies of a mix, recording an eleventh will erase the first. There's also an abort key which scraps the last Write pass you made.
I put it to Jo that although we see demos of automated consoles with all the faders and switches looking incredibly busy all the time, the reality is more likely to be a static mix with just a few faders making occasional corrections and fades.
Jo Jenkins: "I think that's right, so you should be able to get a reasonable number of typical mixes onto a floppy, but the disks are in IBM PC format so you can create backups on any PC or clone. This is useful if you haven't opted for an internal drive."
Who do you see as being the main customers for this type of console, and when will they be able to buy one?
John Oakley: "Initially the DC2000 will be marketed as a multitrack console aimed at the serious home and project studio, but we already see considerable potential in video post production areas. As for availability, the current aim is to start shipping in July."
Soundcraft Electronics Ltd, (Contact Details).
Feature by Paul White
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