You are here

Using An Optically Connected Multi-channel Digital Setup

Wix Wicken: Songs And Visions By Paul Wiffen
Published February 1998

Using An Optically Connected Multi-channel Digital Setup

The spread of the ADAT 8‑channel optical digital interface to studio equipment of all kinds has raised the prospect of a revolution in multitrack digital recording. Self‑confessed digital evangelist (and Korg UK product specialist) Paul Wiffen explains how the optical digital interface and several fibreglass cables made keyboard session player Wix Wickens' life easier at last year's prestigious Songs and Visions concert at Wembley.

Although the eight‑channel optical digital audio interface employed on Alesis's ADAT digital recorder has been in use in studios for several years now, it's only during the last few that manufacturers other than Alesis, such as Yamaha, Emu, Kurzweil, Soundscape and Korg have begun to offer it on synths, mixers, digital multitrack recorders and digital effects units, making an entirely digitally connected multitrack recording setup a reality.

The real advantage of the ADAT optical connections (as I explained in detail in my December 1996 SOS review of the Korg 168RC digital mixer, back in my pre‑Korg days) is that up to eight channels of 48kHz digital audio can be sent down a single fibre‑optic cable. This makes it much more efficient than Sony and Philips's Digital Interface (more commonly known as S/PDIF), which can only transmit two channels, normally a stereo pair, down the same cable. I have been extolling the virtues of an all‑digital system connected in this way for some time now, both as a free agent and during my time at Korg, but no‑one who has benefited from my attempts to convert them to an all‑digital setup has had quite so high a profile as Paul 'Wix' Wickens, who I helped with his keyboard setup for the huge star‑studded Songs and Visions concert at Wembley last autumn.

Wix vs Wembley

Earlier in the year, Wix, (who, in case you haven't heard of him, is famous for his programming, playing and production for artists as diverse as Paul McCartney, Swing Out Sister and Tasmin Archer) was looking at getting into PCI‑based hard disk recording on the Mac. I've been bumping into Wix for many years now (and often had my name confused with his), and he managed to track me down at Korg for some advice. He wanted to "pick my brains" on the various available HD options, and as we talked, I declared my vested interest as Korg's new Soundlink/Trinity/Z1 demonstrator. We agreed to meet up for him to check out Korg's 1212 multi‑channel I/O card, which he was looking to integrate into his Mac‑based Logic Audio setup.

However, when he next rang, it was to tell me about a gig he had just landed at Wembley Stadium, playing behind a list of stars as long as your arm and organised by Tribute, the people behind the Berlin Wall concert and a huge East‑meets‑West affair in Japan earlier in the decade. It was to be a sort of live Rock & Roll Years, with huge screens showing newsreel footage behind a song from each of the last 40 years, and sounded like it could be pretty stunning. As a result, all talk of the upgrading his production setup with a 1212 card had to be put on hold.

Getting Involved

What Wix wanted was not to have to pull his now‑busy production studio apart to do the gig, and would Korg be interested in lending him a couple of keyboards to do the concert with? I had a chat with the powers that be, and organised a Trinity Workstation for him as his main keyboard, which I got ready for him to check out at Korg's HQ.

When he arrived, I was actually working on my demo material for Korg's most recent synth, the polyphonic, physical modelling Z1 (reviewed in SOS October '97), and naturally Wix wanted to try it out. Needless to say, a player of his calibre was soon making the thing sound much better than my humble efforts, and he very quickly established that some of the sounds were just what he was after for the forthcoming gig — the Clavs from the Plucked String model fitted the bill for Stevie Wonder's 'Superstition', one of the songs already decided upon, and another, Chaka Khan's 'Ain't Nobody', would really benefit from the Z1's multitimbral analogue‑style synthesis. The only problem was getting hold of one for Wix in time for the concert — the only two machines then in the country were needed for promotion and reviews in Sound On Sound and other technical mags. I made Wix no promises, but decided to see what I could do.

Clearly, this way of working is suited to the home studio, but there is no reason why it shouldn't form the basis of a live setup as well.

That afternoon, I did my Digital Evangelist bit on Wix. It's a bit of a crusade with me, trying to persuade musicians to abandon cables that buzz, hum and twitter, in favour of the fibre‑optic connections that the ADAT optical interface uses to pass audio channels around in the digital domain, without any possibility of interference from power cables, unshielded audio or video monitors or the various other electro‑magnetic sources in the modern music‑making environment. Wix listened patiently as I described how he could hook the separate outputs of the Trinity (and maybe the Z1, if I could get him one) into a digital mixer such as a suitably‑equipped Yamaha 03D or a Korg 168RC and keep everything pristine, with automated scene changes as often as he liked on the mixer.

Although clearly not inclined towards a full digital baptism on the spot, he agreed to try it out with a 168RC mixer and see if it would be a feasible working setup. He was, however, quickly sold on using the PBS (PlayBack Sampler) option for the Trinity, as he already knew he might need to play back Akai samples at some point in the show. As he didn't want to drag his Akai out of the studio and rely on floppy or hard disk loads, 8Mb of Flash ROM inside the Trinity (so the sounds would stay there even if the power was temporarily interrupted) seemed like just the job.

Wix left with a 76‑note Trinity Pro loaded with the PBS‑TRI Playback Sampler and DI‑TRI ADAT optical I/O options, and the 168RC mixer, and I promised to keep on the Z1 case for him.

Putting It Together

When rehearsals for the Wembley concert started, at Olympic studios in Barnes, I still hadn't managed to assign a Z1 to him permanently. There were machines en route from Japan, but no‑one could be sure when they would land. So I arranged for him to use my prototype unit whenever I wasn't demoing with it and we kept our fingers crossed that the production units would land in time for the gig. The Trinity's PBS‑TRI was loaded with Akai samples for 'Another One Bites the Dust', which Wix had set up across the keyboard on his sampler. Both keyboards were being fed through the 168RC using the fibre‑optic connections, so that Wix was able to use four outputs from each machine, with some sounds bypassing the internal effects of either the Trinity or the Z1 and instead being processed by the dual effects of the 168RC. All this was achieved with just a single optical cable from each keyboard to the desk. The four analogue outputs of the Trinity could all be sent digitally down a single cable, and on the Z1 which only has two analogue outputs, four outputs can be derived digitally. This means you can take some sounds out without effects and add effects or a different EQ on the mixer. As a result, just two optical cables (one from each synth) were feeding eight channels on the 168RC mixer.

Wix in rehearsal for the concert, with the optically‑connected Trinity, Z1, and 168RC.Wix in rehearsal for the concert, with the optically‑connected Trinity, Z1, and 168RC.The only additional connection needed was a BNC cable from the mixer's wordclock Out socket to the Trinity's wordclock In, to pass the wordclock from the Z1 master onto the Trinity, so that the sample rates of all three units were synchronised. Most SOS readers will have sent a single digital signal from one device to another at some time (say a hard disk recorder to a DAT machine), and in this case the DAT machine can sync directly to the incoming digital signal. With a digital mixer, however, several digital signals are being combined simultaneously, and these need to be mixed together into a single digital datastream. To prevent the interference of clicks, pops and other nasty artefacts caused by unsynchronised digital clocks (not to mention the full‑level white noise which can occasionally occur), you have to make sure that all devices in the system are taking their digital clock from one source. This is done by feeding wordclock from one of the sources, in this case the Z1, to the other source(s), in this case the Trinity. However, as the Z1 doesn't have its own wordclock Out socket, the 168RC mixer (which was set up to take its clock straight from the Z1's optical cable and which does have a wordclock Out) was used to pass the wordclock on to the Trinity's wordclock In.

At the couple of early rehearsals I attended, this system was working well for Wix and he was warming to the idea of the all‑digital keyboard rig. The only potential problem area I had foreseen was that, when using the optional DI‑TRI outputs, both the Trinity and the Z1 ignore the setting of their master volume controls (because this analogue control comes after the D/A converters — on all devices with a hardware volume control after the main stereo converter the digital output level is unaltered). I had worried that this might cause him to want to hook everything up with analogue cables, so that he still had the 'safety net' of the main volume controls on each keyboard. However, Wix was using CV pedals on both instruments, and by routing these to individual program volumes he was able to use these pedals as standard volume controls for both keyboards — which is how he usually controls volumes in a live situation anyway. So the change from an analogue to a digital setup didn't even affect the way he deals with live volumes.

Of course, the one fly in the ointment was that Wix was still using the prototype Z1 and as the week of the gig went by, it was looking more and more like he would actually have to use the prototype machine on the big day itself, the Saturday. However, late on Thursday afternoon, the container with the first production Z1 turned up at Korg HQ. On the very evening before the gear was broken down and shipped out of Olympic studios, ready for the 5am load into Wembley the next morning, we were finally able to get a production Z1 unit to Wix. After a quick MIDI dump of all the programs he had tweaked and multis he had setup from the prototype, he was able to use it in the final Olympic rehearsal.

After The Fact

Come the day of the gig itself, the digital keyboard setup performed flawlessly, but in the usual way of things, the keyboards got a bit lost behind a 20‑piece string orchestra, brass section, drums, percussion, and so on. Still, the entire thing was recorded on multitrack, ready for later release as a documentary and video, so hopefully, the keyboard parts on these releases will be restored to their proper place in the mix.

When I caught up with Wix a couple of weeks later, I asked him for his thoughts on this historic gig and the historic first use of an all‑digital keyboard rig live. Here are his comments:

It's a bit of a crusade, trying to persuade musicians to abandon cables that buzz in favour of fibre‑optics.

"I first made the phone call to Korg in pursuit of an easy life, as I wanted to leave my studio setup alone and not be pulling gear in and out. However, as soon as I played the Z1's Clavinet sounds I knew there was a place for it in the gig — and I found the concept of an all‑digital live rig for the first time ever quite intriguing. When Wiff first mentioned it, I decided I wanted to get the constituent parts at my home to try it out and make sure it didn't create more headaches than it solved. The whole project was very much a 'suck it and see' venture, but because I had the time to get used to it, first at home and then in rehearsals, it turned out to be a very clean and neat solution.

"My only reservation was that the fibre‑optic cables looked a bit delicate for the on‑stage environment, because it's not the safest place, but we didn't have any problems, despite having a couple of 5‑metre cables which were, if anything, too long — all 3‑metre fibre‑optic cables had apparently disappeared off the planet overnight! The real advantage is, of course, that you can have really long cable runs, even though I didn't need this capability at Wembley, where I had to keep my rig as compact and neat as possible, so it didn't spill into the brass section or off the riser into the guitarists.

"There was a bit of a learning curve for me, because I wasn't familiar with the 168RC mixer and obviously at that stage only Wiff knew the Z1. The mixer I found fine, but then I do have a few years' experience of finding my way round new gear. There wasn't even a manual for the Z1, but I got on fine with it for what I needed to do. I did a fair bit of subtle sound editing, changing effects, filter settings, and envelopes, and had no problems. By the time a manual actually appeared, I'd already found the way to change anything I needed to. Obviously, things might have been different if I'd had to make sounds up from scratch, but then Wiff had shown me the Mac editor, which I could have used if needed."

"On the day however, in the pressure of a live gig before thousands of people, the most important thing was that there was no real difference operationally between the all‑digital setup and a conventional analogue mixing situation. Sure, there were far less cables between the keyboards, and those cables were made of glass, not metal, but as far as using the rig was concerned, when I wanted more of the Z1 in the mix, I moved a fader labelled 'Z1' and the same for the Trinity. Obviously, the ability to pair channels and move a single fader is an advantage over an analogue desk, but the main thing for me was that I didn't have to change the way I work to accomodate the technological advance I was enjoying the benefit of. For this reason as much as any other, I would recommend this way of working to anyone."

Clearly, Wix was being truthful here, as a few weeks later he used exactly the same rig for Sir George Martin's Music for Montserrat concert at the Royal Albert Hall, playing alongside Eric Clapton, Mark Knopler, Phil Collins, and host of other stars.

The Way Forward?

For those of you reading this who are interested in getting into the same kind of setup, all you need is keyboards which have the ADAT optical interface (including Alesis' own QS range, the Korg keyboards mentioned here or any of Kurzweil's K‑series synths fitted with the multi‑channel interface option) plus a digital desk from either Yamaha (fitted with the optical option) or Korg. Both the Yamaha and Korg desks have analogue inputs, so any bits of gear which you cannot interface digitally can be added in in the conventional way.

Clearly, this way of working is ideally suited to the home studio, but there is absolutely no reason why it shouldn't form the basis of a live setup as well, as Wix's experiences prove. As far as Wix's misgivings about the fragile appearance of the fibre‑optic cables are concerned (and an optical cable hasn't failed on me yet), I noticed when I was at Studiospares the other day that there are now several companies making much more robust optical cables for live use, so they clearly think this way of working has a future in the stage environment as well as in the studio.

Published February 1998