Lexicon PCM96

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Reverb Processor

Published in SOS November 2008
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Reviews : Effects

I'm old enough to have used real reverb plates in earnest, and I can still remember the amazement I experienced when the first digital reverb processors started to be bolted into control rooms — the Quantec Room Simulator, the Ursa Major Space Station, the EMT 250, the Klark Teknik DN780, the AMS RMX16, and the various Yamaha REV and astonishingly cost-effective SPX models. Technology has, thankfully, moved on a long way since then, and so has the way we now work to record and process audio. Where it was once mandatory to have at least one hardware digital reverb in the control-room rack, these days most people probably find it easier and faster to use plug-ins as part of the 'in-the-box' DAW mixing experience.

However, good reverb is extremely processor-intensive, and despite the continual development of computer speeds and capacities, good hardware reverbs often still sound better than their plug-in equivalents. The problem is that they aren't as convenient to use, or as cheap, and you have to note down the settings if you expect to revisit the mix at a later date.

Rather than clog up the computer's processor(s) with number-crunching reverb algorithms, a better solution is to install a dedicated DSP card to do that work separately — such as the TC Electronic Powercore card, for example, which runs the same algorithms as some of TC's hardware reverbs. This approach has the advantage that the computer can get on with the routine business of audio-file manipulation and data transfers, rather than having to concern itself with the hugely calculation-intensive task of reverb processing, yet all the settings and parameters of that reverb can be controlled from within the DAW, as well as stored and recalled as part of the project. No more twisting around the rack to adjust a parameter, and no more note-taking of settings at the end of the session.

This installed DSP-card approach is one which has been widely embraced by those who demand a lot of their computer DAWs, but it still isn't the perfect solution for everyone — not least the manufacturers who are increasingly having to offer both traditional hardware reverbs (largely for the live sound industries) and computer cards to satisfy the DAW market. One solution is to produce hardware reverbs that can be integrated easily into the DAW, and that's exactly what Lexicon have done with their new PCM96 reverb and effects processor.

Overview

The PCM96 is a standard 1U rack-mounting device that extends 280mm behind the rack ears (not including the connectors), and weighs just under 4kg. It runs cool, and has only side vents, so it can be installed in racks with other equipment above and below it without problems. And if you squint into the side vents while the machine is powered up you'll see a most impressive disco light-show going on — this thing must have funky DSP chips! Actually, the large and densely populated motherboard carries a Motorola MPC5200 embedded processor, an Altera Cyclone FPGA, and an Analogue Devices Tiger SHARC — plus all the usual circuitry for the various interfaces. The switched-mode power supply looks like an OEM module bolted onto the chassis alongside the motherboard, but the construction throughout is to very high standards, so the PCM96 looks likely to be very reliable.

Once connected to your Mac, the PCM96 can be used just like any other DAW plug-in, although the hardware nature of the processing means that the number of plug-in instances is limited. Once connected to your Mac, the PCM96 can be used just like any other DAW plug-in, although the hardware nature of the processing means that the number of plug-in instances is limited. Once connected to your Mac, the PCM96 can be used just like any other DAW plug-in, although the hardware nature of the processing means that the number of plug-in instances is limited.

As its name suggests, the processor can accommodate sample rates up to 96kHz, and it uses 32-bit floating point processing. The new machine ships with over 1200 factory presets built from a set of 28 reverbs, delays and modulation effects — some brand new, and some previously loved Lexicon classics. There are two interesting new facilities: versatile EQ filters, which can be used to shape the audio within an effects chain; and an 'Infinite' function, which enables the selected reverb to continue endlessly — something that Lexicon offer as a means of 'creating unusual backgrounds and sound effects'.

The front panel is very simple, with a stereo bar-graph meter, a delightfully crisp and clear OLED (Organic LED) alphanumeric display, one large and three smaller encoder knobs, and just six push-buttons. There's also a slot for a Type I Compact Flash card which can be used to store program presets (up to 1536, in fact), and the unit's internal Flash memory can store 768 user presets. The rear panel carries the mains IEC inlet (the power supply accepts voltages of 100-240V AC), two RJ45 (10/100) Ethernet ports, two Firewire 400 ports, and the usual trio of MIDI sockets. There's also a word-clock input, single (two-channel) AES3 sockets for digital audio in and out, and a pair of analogue inputs and outputs on XLRs. The analogue I/O can be switched between +4dBu and -10dBV nominal levels, and in the former 0dBFS equates to +20dBu. The 24-bit converters provide 115dB of dynamic range (A-weighted), with a bandwidth extending between 20Hz and 40kHz (-3dB). Worst-case propagation delay at a 44.1kHz sample rate is 2.4ms going analogue-analogue, and 0.5ms going digital-digital, both reducing by about 40 percent when operating at 96kHz. Of course, propagation delays aren't really relevant to reverbs (they just extend the 'pre-delay' fractionally) but can become relevant for other effects, especially if you plan to mix the direct and processed versions of the source signal externally.

The processor can be controlled from its front panel, or remotely via Ethernet, Firewire or MIDI. The Ethernet and Firewire options require the supplied PCM96 plug-in to act as the control interface. This is currently only available to Mac users (OS 10.4.9 and higher), and has only been tested with Pro Tools 7.3 and above (both HD and LE versions), and Logic 8 (see Paul White's description in the box on the previous page). Lexicon are considering porting the code for Windows too, and suggest there may be developments 'in the second half of next year'. The Ethernet interface also supports HiQ network installations, which extends the PCM96's appeal in live sound applications.

In Firewire mode, an additional option is presented, which is to stream audio and control data via the Firewire interface. This fully integrates the PCM96 as a DAW effects plug-in for any program that's compatible with VST or Audio Units. (An FXpansion wrapper is also included to enable operation with the Pro Tools RTAS format.) Better still, working in the 'Firewire with audio' mode provides up to four audio channels in and out of the Lexicon, instead of just two.

Top: The PCM96 is controlled largely by the main shuttle wheel, but the three smaller knobs also give you direct access to the most commonly used parameters, with a press of the first mapping those knobs to further parameters. Above: Rear panel. Top: The PCM96 is controlled largely by the main shuttle wheel, but the three smaller knobs also give you direct access to the most commonly used parameters, with a press of the first mapping those knobs to further parameters. Above: Rear panel. Top: The PCM96 is controlled largely by the main shuttle wheel, but the three smaller knobs also give you direct access to the most commonly used parameters, with a press of the first mapping those knobs to further parameters. Above: Rear panel.

Internally, the PCM96 can provide up to four separate processing engines or 'machines.' Using the dual-channel physical I/O on the unit itself, these can be configured in six ways, with single or dual machines per channel, and stereo or dual-mono inputs. The simplest set up uses a single engine to provide stereo-in, stereo-out effects, and its dual-mono equivalent uses two machines. Some of the more complex configurations provide two cascaded engines for a stereo-in, stereo-out format, or four engines for the dual-mono equivalent. There's also a combination with dual-mono inputs feeding separate machines, their outputs being fed into a third stereo-in, stereo-out machine. In the Firewire 'Control and Audio' mode, those cascade configurations are not available (although you could route signals in the DAW to achieve much the same thing), but you can run plug-in effects using one or two stereo machines, two or four mono, or two mono and one stereo machines.

The algorithms and factory presets are all that you'd imagine them to be, and they're grouped into the usual Halls, Plates, Chambers and rooms — all with small, medium and large subsets. Lexicon's lovely stereo Concert Hall algorithm is included, and there are also categories for Room Environments, Chorus/Flange, Delay, Resonance and Reverse. I couldn't find the PCM90's 'Deep Blue' reverb algorithm that makes my keyboard playing more tolerable... but there was no shortage of equally complementary presets.

In Use

It was a simple matter to hook up the new machine alongside my old and battered — but still much loved — PCM90, to compare and contrast the old and new, via both the analogue and digital I/O. The first thing I noticed was just how long it takes the PCM96 to boot up. My old PCM90 boots and restores the previous preset in 28 seconds. The PCM96 (running current v1.2.7 firmware), takes a beard-growing 75 seconds to boot up — which is substantially slower even than my quad-core Vista PC! The analogue I/O was quiet and clean, with plenty of headroom, and the -10dBV option means that even semi-pro setups can use the dynamic range of this unit effectively. The digital I/O and the external word clock worked without any problems at both standard and double sample rates.

I quickly discovered how to navigate around the machine's configuration and operational parameters without having to resort to the manual. The operation is very logical and intuitive — and fast. Turning the large dial scrolls through the presets in the current subset (for example, large halls) and pressing it loads the currently displayed algorithm. The Back button exits to a menu showing the other effects subsets, which can be searched and selected using the large encoder, again. Editing parameters on the PCM90 is not quick and easy but the PCM96 improves on that enormously, with the three smaller encoder knobs providing instant access to the three most commonly used parameters. In the case of a hall reverb, that's pre-delay, reverb time and the high cut-off frequency — but pressing the first encoder knob then displays the next three parameters, and further clicks access further parameters. All very simple and extremely intuitive.

The reverbs have that classic Lexicon character. The shorter settings work very well to add life, space and depth to dry sources, but without filling the mix with stodge, while the big reverbs have that lush, better than real-life quality we associate with Lexicon reverbs. The other effects are very good, too — they're all very usable and some are very interesting, such as the resonant chord effects — but I suspect few will buy this processor specifically for them.

The live sound, theatre and broadcast markets still favour hardware reverb processors and, as I mentioned earlier, the PCM96 is clearly geared up to satisfy that demand, as the 96kHz, Ethernet and HiQ features indicate. But the inclusion of Firewire control with audio streaming also enables the PCM96 to integrate superbly well into the DAW environment (see 'PCM96 As A Plug-in' box), and that makes it unique and highly desirable. It is just a shame that it is only Mac-compatible at present.

This is an impressive-sounding, and impressively flexible reverb machine. It may be twice the price of a PCM91, but it also provides twice the facilities in Firewire mode — and it is twice as flexible! The PCM96 is well worth serious consideration if you're looking for a high-end reverb processor to work with your DAW. 

Alternatives The quality of a reverb is, by its nature, subjective, and if you're looking simply for a professional-quality outboard reverb you could consider other Lexicon units, as well as models by TC Electronic and Bricasti. The PCM96's feature set makes it unique, though, because no other hardware reverb I know of can be integrated so completely into a DAW. The closest comparison is with dedicated DSP cards, such as the TC Electronic Powercore, which potentially offer more reverb instances but can't be used as stand-alone devices in the way the PCM96 can.

The PCM96 As A Plug-in Lexicon were one of the first companies to recognise that hardware would be an easier sell if it integrated more effectively with the software studios currently dominating the marketplace. After all, software DAWs host plug-in effects, so why not make your hardware look like a plug-in as far as the user is concerned? Lexicon tested this approach with their lower-cost MX200 and 400 processors, but this is the first time they've used it for one of their flagship professional products. The idea is that you hook up the PCM96 to a Mac (no PCs yet, I'm afraid) using Ethernet or Firewire. The latter enables four channels of audio streaming, as well as computer control over the PCM96. The control window looks like a conventional software plug-in, and appears when you select a Lexicon effect from your plug-in list. As with a conventional plug-in, any changes made to the settings are saved with the song file or may be saved into the plug-in's user-preset list. While the analogue I/O allows effects to be cascaded, the Firewire mode is strictly one effect type per plug-in — but you can, of course, cascade them by putting one instance after another. The routing options available in this mode are: two stereo effects; four mono effects; and two mono effects plus one stereo effect. Once you've used up the available four input and output streams, that's it — as the PCM96 that's doing the processing is hardware, you can't just keep on opening plug-ins until your CPU melts! When the plug-in is active, the display of the PCM96 changes ('Application Lockout') to show that the front-panel controls are now inactive, and that control has been handed over to the plug-in. Where you prefer to use the plug-in only to control the PCM96 and to stream the audio via the two analogue inputs and outputs, you can switch to 'Control Mode only', in which case the routing options are the same as for stand-alone operation. In either case you don't have to mess around creating aggregate drivers because the PCM96 software communicates quite transparently with the DAW when your usual audio driver is selected. Lexicon have really worked hard to make the PCM96 less daunting than the earlier PCM90 and 91, and the plug-in control is extremely well set out. An arrow tab below the simplified front-panel graphic in the plug-in window brings down a LARC-style (Lexicon Alphanumeric Remote Control) control panel, with the most commonly used controls for the particular effect type mapped to eight sliders. Another arrow tab at the bottom of this window opens another panel with further controls, initially relating to input and output levels, as well as displaying a line of buttons that take you to different editing areas for the effect. For example, if you have a reverb loaded, you can choose to show the I/O settings, Input Control, Shape, Control, Reflections, Echoes, Early Shaping and Shaping parameters on the lower panel. This is very fast and intuitive — quite unlike the 3D spreadsheet approach of the PCM91. While this all looks straightforward, my initial experiences when trying to use the 'plug-in' in Logic Pro 8 on my Macbook Pro (Mac OS 10.5.4) and on my Studio G5 (running OS 10.4.11) were frustrated by crashes, freezes, grey screens of death and a smug refusal to do business... until a call to Lexicon's product specialist revealed that there was a software update available for both the plug-in and the PCM96's firmware. Once I'd installed the updates, things went much more smoothly and the only way I could make the thing crash on my Macbook Pro was to try to switch from 'Control Only' to 'Control and Audio' mode using the Lexicon control panel in System Preferences while the DAW is running — which, of course, is something you wouldn't normally want to do! Part of the Control Panel setup allows you to choose a small, medium or long buffer setting, so that in marginal situations you can increase the latency if you're experiencing audio glitching — but I had no problem using the default setting. Some small latency is inevitable with any external Firewire audio device but most DAWs will compensate for it, so if you're only using the PCM96 for mixdown, you shouldn't have any problems. If your DAW doesn't compensate for the extra latency, then a few more milliseconds added to your delay time or reverb pre-delay shouldn't be a huge worry in practice. On my G5, the current PCM96 software still refuses to play nicely when my TC Konnekt 48 is also connected, crashing the Mac on startup, but it works fine with other interfaces, so there's a conflict going on somewhere that needs to be resolved. I noticed a CPU-load spike when I hit the play button part-way through a song, which didn't occur without the PCM96 plug-in running, and this is something to bear in mind if your project is running near its CPU capacity. Engaging or bypassing the plug-in during playback can also cause big CPU surges, but once playback has started the additional CPU load seems negligible. Overall, I found that the operating experience was just like having the best reverb plug-in in the world — which I suspect will prove to be a big temptation for serious DAW users. Paul White

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