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Line 6 StageScape M20D

Digital Mixer With Multitrack Recording By Paul White
Published November 2012

Can you really make a complex, DSP-packed mixer that even musicians with no engineering experience can use? Line 6 think they can...

Line 6 StageScape M20D

Line 6 made a bold entry into the live sound arena with the announcement, at this year's Winter NAMM show, of the StageScape mixer and StageSource PA speakers. I spoke to one of Line 6's founders, Marcus Ryle, about the new launches back in SOS April 2012. You can read that interview at /sos/apr12/articles/line-6-tech-interview.htm. In this review, I'll look more closely at the StageScape M20D, a 20-input digital mixer with an innovative touchscreen interface. The M20D can be used on its own or, using the L6 Link, in tandem with a set of StageSource speakers (see 'Speaking To Speakers' box). We'll review the speakers themselves another time.


Many musicians have to mix their own gigs from the stage, and such users appear to form the prime market for the M20D — although it's perfectly capable of acting as a front-of-house mixer, or being put to use in installations, as long as the input channel count is sufficient.

Apparently, Line 6's aim was to produce a fully featured digital mixer where most of the clever stuff was looked after either automatically, or via source-specific presets, so that musicians with less mixing experience than a dedicated FOH engineer could still achieve good results. All the tools that professional sound engineers are used to are also here, though, and can be accessed via channel presets, simplified 'Quick Tweak' adjustments, or full-on 'Deep Tweaking'.


Cosmetically, the M20D is rather unconventional, with its massively thick metal front panel, two rows of six variable-colour, illuminated push encoders and a seven-inch resistive colour touchscreen. There are no faders and very few physical buttons: five mode buttons occupy the space to the left of the screen, with just two to the right. Below and to the right of the screen is a large rotary control.

We're on more familiar ground with the I/O panel, where we find 12 'combi' mic/line inputs (with phantom power switchable in banks of six), four jack inputs, XLR outputs for the main stereo outputs and the four monitor feeds, and a headphone outlet with its own volume control. There's also an auxiliary stereo mini-jack input, two footswitch jacks, an XLR for the L6 Link, a USB port for a memory stick, hard drive or Wi-Fi adaptor (for controlling the mixer wirelessly from an iPad), an SD card slot, and a further mini USB port for PC connection. Power is delivered via a standard IEC socket and, being universal, the internal PSU will adapt to all common 50/60Hz mains voltages.

The 20-input designation comes from totting up the mic/line inputs, the line inputs, the aux input and two-track playback from card or computer. Stereo audio streamed via a USB stick or SD Card comes into the mixer on its own channel, while audio delivered via USB from a computer comes through the stereo aux channel, and is summed with any analogue signal that's present there. Although they don't provide phantom power, the jack-only inputs will still accept mic-level signals, so you could use them for dynamic mics, as well as modelling preamps, keyboards, electronic drums and so on.

Under The Hood

All of the M20D's inputs and outputs reside on the top panel. The only physical controls are the 12 encoders, seven switches and the large rotary control.All of the M20D's inputs and outputs reside on the top panel. The only physical controls are the 12 encoders, seven switches and the large rotary control.

The M20D's visual mixing environment employs friendly graphics designed for intuitive control of the extensive DSP, which includes processing on every mic/line channel. The processing includes 12-band automatic feedback suppression, de-essing, dynamics (gate, compressor, multi-band compressor and dynamic EQ), sub-bass boost, four send effects and a full EQ (shelving lows and highs plus up to four parametric mids, as well as an input stage low-cut filter).

The jack-only inputs have slightly simplified processing options, but still have a full EQ section and a compressor, as well as access to the four effects sends. The effects engines include all the usual suspects: reverbs, delays, vocal doubling, modulation effects and so on.

In addition to its mixing capabilities, the M20D lets you record gigs as multitrack audio files onto an SD card (Class 10 or faster), a non-bus-powered USB hard drive or a computer. Up to 20 individual files can be recorded: all 16 inputs, plus the stereo aux input and the main mix. The recordings are 24-bit, and fixed at 48kHz, which is the sample rate that the internal processing runs at. The lack of a 44.1kHz option is a bit of an irritation, but then most DAWs will sample-rate convert as necessary if you want to burn a CD. The SD card is perhaps the most practical recording option, as it leaves the USB port free for plugging in a Wi-Fi dongle.

The M20D also has enough internal memory to record a 20 second 'Quick Capture' loop of a live performance, so that you can loop a section of the performance while checking the balance from out front, which could be very useful.

The five mode buttons to the left of the screen select various configuration pages, called Setup, Tweak, Record, Monitor and Perform. Setup is where you assign inputs and match them to channel presets, with the opportunity to move their corresponding icons around on a 'virtual stage' screen. Tweak houses the channel-strip view, where you can adjust levels, pans, sends and channel DSP processing. Record is where you can initiate a recording or Quick Capture session, and Monitor lets you configure the foldback mixes. The Perform screen is the 'main' real-time mixing environment.

Over to the right of the screen are buttons labelled Mute Mics and Mute All. When the latter is activated, all the mic inputs go into mute mode (although you can modify the settings to create a specific mute group), and then individual mics can be unmuted for making announcements between sets. The Mute All button is a mechanical switch that kills all the outputs.

Getting Started

The Perform screen is where most of the real-time mixing takes place. Input channels and monitors are represented by icons on a virtual stage, and touching those icons selects them for editing.The Perform screen is where most of the real-time mixing takes place. Input channels and monitors are represented by icons on a virtual stage, and touching those icons selects them for editing.

The first step in operating the mixer is to use Setup mode to establish what is connected to the mixer, and which factory presets offer the best starting point for the various instruments and voices. There's a miniature graphic of the connection panel at the top of the screen, and the various sockets light up in colour as plugs are connected to them. Because only channels with plugs inserted appear in the mix, the screen remains uncluttered, and each on-screen icon has its input-channel number flashing above it. If you touch the input strip at the top of the Setup page, it expands in size, giving access to the phantom power switches, the footswitch setup page and the L6 Link setup page.

Thanks to its input auto-sensing capability, the M20D automatically creates a default mic or line icon whenever a mic or jack is plugged into an input, and you can change that icon by choosing from the range of presets arranged along the bottom of the Setup screen. Icons are available for almost any instrument: there's even one for bagpipes, although one might suggest that the appropriate DSP processing in this case constitutes a permanent mute! There are also presets to cope with stereo input sources, in which two adjacent channels are linked.

When you choose a new icon, the selected channel not only switches its icon to match your selection: the factory settings deemed appropriate for that sound source are also loaded into the channel. The touchscreen then displays the relevant icons on a virtual stage, each representing a performer or instrument, and these icons can be dragged around the virtual stage to represent the physical position of the performers. There are even visual representations of any monitors you may have plugged in, which, again, can be moved around the virtual stage.

Perform Mode

The Quick Tweak screen is intended to make it easy for non-engineers to adjust channel settings. Here, the processing for a bass preset has been simplified to an XY pad, with Boom, Snap, Smack and Scoop descriptors.The Quick Tweak screen is intended to make it easy for non-engineers to adjust channel settings. Here, the processing for a bass preset has been simplified to an XY pad, with Boom, Snap, Smack and Scoop descriptors.

With the Setup process complete (and it really is an easy and painless process), the next stage is to dip into Perform mode. This, again, displays the virtual stage, but the icons are locked into position, and the I/O panel and configuration options found in the Setup page are absent.

Along the bottom of the Perform screen you can view the levels for each source, the monitor sends and a mute button for each channel (the mutes can be toggled to show solo buttons instead). Touching one of the channel icons selects it for adjustment, causing the appropriate encoder to glow. Channel selection can also be done by using the Channel Selector window in tweak view. Double-clicking an encoder knob resets its value to 'neutral', while double-clicking the Perform button always brings you back to the 'levels' view when in Perform mode.

A stereo meter to the right of the screen shows the main mix level, and if the mix gets too busy for all the controls to fit on one screen, you can scroll in traditional iPad style by touching and dragging.

Le Tweak, C'est Chic

Adjustments beyond volume are made by pressing the Tweak button and then deciding whether to use the Quick Tweak or Deep Tweak modes, selected once you're in the Tweak screen. In both Quick and Deep Tweak screens, buttons along the top allow you to choose what channel you're tweaking, and also adjust or change that channel's preset. The channel pan takes the form of a horizontal slider at the bottom left of the page. In Quick Tweak mode, the vocal channel processing is shown as section buttons along the left-hand side for Punch (dynamics), De-esser, Tone and Global FX. Touching any of the processing buttons brings up an X-Y Tweak Pad, essentially a virtual joystick, where you simply drag a finger toward common sound descriptors such as Bright or Dark. These terms change depending on the instrument type you've selected for the channel, so if you're working on a kick drum, for example, you'd see terms such as Boom, Snap and Scoop — terms musicians can relate to. As you move your finger on the screen, the software then adjusts multiple parameters on your behalf to achieve that sound.

Experienced engineers can use the Deep Edit mode, where the processors look pretty much like conventional software plug-in windows, with traditional controls and familiar terminology. This screen shows all the separate insert effect blocks, which for our lead vocal are Input, Gate, De-esser, Dynamic EQ, Compressor and EQ.

When in any Deep Tweak window, the lights on the encoders below the display change colour to match their on-screen function. Parameter adjustment can then be done using either the knobs, or by touching and dragging grab points on screen.

Gain Control

Now I know what you're going to ask: how do you adjust the input gain trims if there are no gain trim pots? There are two options, both controlled from the screen. One is to go to the input block in the Setup page, and then adjust the input gain manually while watching the on-screen meter. The other is to activate the Auto Trim mode (also available in the Setup page), which essentially listens to a sample of you shouting or playing your loudest, then sets the gain for you, leaving a sensible amount of headroom. In the latter mode, you can activate whichever channels you wish to be Auto Trimmed and do them all together. Auto Trim is a good option to use, as it ensures the input levels are in the right ballpark to allow any presets that include compression (or any other process with an adjustable threshold) to work correctly.

And there's more: you can also switch on Trim Tracking, which keeps an eye on your levels during performance and, if the input level gets too hot, automatically turns the input gain down and the output level upwards to compensate, maintaining the same level in the mix. This makes it impossible to drive the mixer into clipping unless you physically overdrive the mixer's input stage, which takes a lot of doing.

While you're in the Setup section, you can also enable the anti-feedback option, with its 12 feedback-seeking filters, and dial in a low-cut filter frequency of your choice. The anti-feedback processing is applied to individual channels, rather than globally.

Monitor Mixing

More experienced engineers can use Deep Tweak mode, where all of a processor's parameters can be freely adjusted, in a manner familiar to users of plug-ins. Here you can see the M20D's multi-band compressor (top) and parametric EQ.More experienced engineers can use Deep Tweak mode, where all of a processor's parameters can be freely adjusted, in a manner familiar to users of plug-ins. Here you can see the M20D's multi-band compressor (top) and parametric EQ.Line 6 StageScape M20D

Like the inputs, the monitor outputs (and headphone jack) are auto-sensing, so a monitor icon appears on screen automatically when you connect something to a monitor output XLR. You can then drag it on your virtual stage to match its position on the real stage.

In the Monitor screen, the currently selected monitor has four cursor arrows rotating around it, while at the bottom of the screen are the various mixer channels that can be fed to it. The physical encoders relate to the two rows of sound sources shown on the screen, and the caps of all the active knobs glow blue. Effects can be added into the monitors by using the FX To Mons tab at the top left.

The typeface is a little small, but you don't have to worry about reading too much, because to turn up the amount of vocal in the selected monitor you can simply touch the icon of the vocalist and the appropriate control knob will glow more brightly than the rest, indicating that it is the one you need to adjust. One cute touch is that whenever you adjust a monitor send, an on-screen line temporarily appears linking the relevant monitor to the performer or instrument whose sends are being tweaked — a useful visual confirmation that you are adjusting the correct level.

There's even a 'quick and dirty' Linked monitor mode where you can link the monitor levels to the channel levels, which is a good way to set up a rough monitor mix before the individual performers start asking for more of themselves. When a channel is in Linked mode, the channel level is displayed along with the monitor level, and the two levels retain their relative settings when the channel level is adjusted, which must mean that the monitor send is taken post-fader. When a channel is in Unlinked mode, its monitor level is independent of its channel level, as per usual pre-fader operation. Being ever-helpful, most input channels default to being in Linked mode, although channels designated to sources that are usually loud on stage, such as guitar amps, default to being unlinked.


If you want to record the gig, it's on to the Record page. There are three main recording modes: Quick Capture (as mentioned earlier), Record and Stream. Record saves the audio files to a USB drive or SD Card, and Stream sends the audio to a computer via USB. A button at the top of the Record page, marked Configure Record/Playback, lets you choose what to record (either inputs only, main mix only, or inputs and mix), name the recorded files, and choose where to save them. The individual channels are all recorded pre-fader and without effects, while the main mix record feed is taken post-fader, and with all the signal processing.

If you want to do a Quick Capture recording to check the balance, you can get to this quickly from the Record page. From there, pressing Record captures up to 20 seconds of multitrack audio to internal memory, which, when played back, will loop until you stop it. This also records without processing, but plays back via the mixer's DSP, allowing you to adjust the mix as you listen from out front. You can also use Quick Capture on individual channels, via the channel's Quick Tweak screen.


The M20D combines some truly innovative and user-friendly aspects: auto gain trimming, Quick Tweak editing and friendly graphics to name, but a few. There are some notable omissions, but as this is the first incarnation of the software, future updates can address most operational issues. The most obvious to me is the lack of a dedicated effects bypass button on the Perform screen to kill all the effects between songs, and there is room in the header bar, should the designers choose to add one. You can assign one of the footswitch jacks to effects bypass, but if you also want to use footswitches to move up and down through Scenes, both footswitch jack inputs will already be tied up. In the interim, however, it is easy enough to create a group for the effects returns (see 'Channel Groups' box).

I'd also like to see the name of the current Scene in the Perform screen header bar, as if you're using the footswitches to change scenes it would be embarrassing to navigate to the wrong one and not realise it! Another helpful feature would be multiple versions of a Scene, with different level and send settings, that could be switched directly from the Perform page, to bring the guitar up a little for a solo and maybe add a bit more delay to it (for example). Four variations would meet most needs, and would save you having to try to switch complete scenes mid-song, when all you really need is a different set of fader and send levels.

There's no getting away from the small screen size, however, and this is no bigger on the iPad app (see 'iPad Control' box) than it is on the hardware, as the virtual knobs and buttons take up the rest of the screen (although the app does at least allow you to zoom in, which hides the buttons to the left of the screen but keeps the main display and encoders). Everything is very clear, but those with less than youthful eyesight may benefit from reading glasses, and readability will almost certainly be harder in daylight conditions too, so you need to find a shady spot to mix those outdoor events. Fortunately, however, you can perform most key operations via the graphics rather than having to read labels.

Of course, it is part of my job to pick away at weak areas and to highlight potential problems, but this mixer does incorporate a lot of really good ideas that put a lot of processing power in the hands of the musician, while keeping operation outwardly simple.

The auto-sensing inputs and Quick Tweak modes, for example, are exceptionally practical, and I can envisage even experienced users using Quick Tweak as a way to fine-tune settings very quickly. The various sections are laid out logically, and I found my way around the essentials of the mixer fairly quickly without having to refer to the manual. Quick Capture is a great idea, although in most smaller venues it isn't really going to tell you how you sound out front, as a significant contribution to the 'out front' sound inevitably comes from the backline. Being able to record all your gigs as multitrack files is incredibly useful, though, even with the fixed 48kHz sample rate.

Line 6 Appeal?

Whether this format of mixer takes off depends very much on whether musicians and engineers are prepared to accept a departure from the traditional 'row of faders' format, but only a few minutes spent with the M20D should be enough to convince people that its operation is, indeed, intuitive. For smaller gigs, where the backline level may vary (usually upwards, in my experience!), the ability to adjust levels very quickly is paramount, and using the rotary encoders this is easy, even though you're using knobs rather than faders. The Scenes are useful as starting points, and can at least ensure you have the right effects set up and any unused mics muted, but as Field Marshall Helmuth Carl Bernard von Moltke famously put it, "No battle plan survives contact with the enemy!”. For theatre use, though, or for any other event that will be repeated, Scenes offer a big advantage.

Finally, there's the format and the price. The on-board features are certainly comprehensive and should be enough to satisfy the most geeky sound engineer, as long as having 16 inputs to mix is enough. For small bands, conference work and some installs, this will be the case, but for larger venues, the lack of any way to expand the mixer (other than by feeding a separate desk into a pair of jack inputs or the stereo aux input) sets a limitation. There's no reason not to do so if you need more inputs, however, as not every voice or instrument will need all the resources the M20D has to offer. And the price? Certainly, it isn't unreasonable for what you get, but for the amateur gigging band, in the UK at least, it is probably more than their typical budget for an entire PA system, so the potential market base amongst 'ordinary musicians' may be narrower than Line 6 might have predicted.

Bands working on a more regular basis might well see the appeal, though, not least for the way it can simplify setting up, and negate the need for extra hardware. The M20D also lets musicians, who may not be experienced sound mixers, get great results. Of course, it will appeal to those who wish to record their gigs — adding a dedicated multitrack recorder is both costly and adds complication, whereas here you get a simple one-box solution. The Rehearsal room that wants to offer recording facilities will also be a prime market, as will smaller theatres or music clubs that have backline permanently set up for visiting musicians.

Then there's the cost saving (and setup time saving) on a multicore if you can have somebody out front with an iPad making any necessary mix adjustments. The inclusion of active feedback suppression also saves on the cost of buying outboard gear that then takes up more space and has to be connected using a mess of cables.

Summing Up

The overall sound of the mixer, and the thought that has gone into the creation of the presets, is impressive, and there's more than enough processing on board to ensure you get a polished result, even if you aren't a skilled mix engineer. Summing up, then, while the format and price of this mixer means that it won't suit everyone's needs or budget, it is an extremely sophisticated piece of kit that incorporates many facilities you'd need a rack full of outboard gear to provide in the analogue world — which would probably far exceed the cost of the M20D. A lot of work has gone into the user interface, which is seriously clever and veering towards brilliant in parts, and the sound quality is clean, with very capable effects covering all requirements.

I see the M20D as Line 6 making a statement of how capable and innovative they are at the professional end of the live sound market, and also as a development platform from which other products must inevitably emerge.  


In the iPad-controlled mixer stakes, the nearest equivalent is the Mackie DL1608, though that adopts a far more conventional mixer paradigm and has fewer on-board processes. The PreSonus StudioLive digital mixers can also be controlled via an iPad, but require a laptop to be connected to the mixer.

Global Effects

There are four global effects blocks in the M20D, each fed from a separate post-fader send. Touching Global FX (accessed via either of the Tweak modes) shows four send faders, along with the names of the effects being fed, and touching the effect name area then brings up further effect options that may be loaded in place of the current one. The first effect block is dedicated to high-quality reverbs, block two is also dedicated to reverbs but with fewer choices, while block three offers chorus, doubler, flanger, or 'four voices', which is a kind of doubled doubler. The final engine is where you'll find a choice of four different delay types.

Effect adjustment can be done via Quick Tweak or Deep Tweak modes. In Quick Tweak mode, for example, reverb is simplified to a trackpad steering between Far, Space, Short and Long. Even in Deep Tweak mode, however, the effects are pretty user-friendly, as most have just a few sliders addressing the key parameters.

Speaking To Speakers

When the StageScape M20D is hooked up to Line 6 StageSource speaker systems via L6 Link, it recognises which loudspeakers are being used as mains and which as monitors (ie. those that have been placed on their sides), and then routes the monitor feeds automatically. The main PA speakers self-configure according to whether a sub is in the system, whereupon it will automatically set the digital crossovers. The system will also automatically switch between mono and stereo operation, depending on how many front-of-house speakers are plugged in. The graphic EQ built into the speakers may also be accessed via the mixer, to help smooth out room problems.

iPad Control

With a Wi-Fi 'dongle' plugged in to the M20D's USB port, all of the mixer's functions can be controlled remotely using an iPad. The iPad must be running Line 6's StageScape Remote app, and you need to enter a four-digit security number, which is found in the M20D's System Settings page.

StageScape Remote displays a birds-eye view of the mixer, including the screen, the five buttons to the left of it, the master level knob and the 12 encoders (in other words, you see the whole mixer front panel, other than the two physical mute buttons). The display view on the iPad can be different from that of the mixer itself, so, for example, one person could be running the mix from the M20D, and another looking after the stage monitor mixes via an iPad. In fact, the M20D supports the use of multiple iPads, so multiple performers could adjust their own monitor mixes. For peace of mind, I'd like to see a means of limiting parameter access to individual iPad users, so that they can only mess with their own monitor mix and no-one else's — and certainly not the main mix! Perhaps a simpler 'more me/less-me' iPhone app would make sense for personal monitor adjustments?

Not all Wi-Fi dongles are compatible with the mixer, but there's a list of suitable models on the Line 6 web site. Using a dongle supplied with the review system, I had the system working on an iPad 2 and an iPad 3. The mixer now supports some USB to Ethernet adaptors, as well, so you can plug the mixer into a Wi-Fi router and run an Ethernet cable to position the router closer to the mixing position for better wireless performance.

Power Outage

In the event of a power outage, the M20D gets you back to the Scene you were running when the power went off, but in my tests the restart time was about 30 seconds — which can feel like an awfully long time! This is a potential problem for all digital mixers that have such a boot-up time, and taking a power feed from somewhere not likely to get shut off is a must.

Channel Groups

Channel grouping is available for controlling the level of something like a multi-miked drum kit or a set of backing vocal mics from a single encoder. Double-tapping an unassigned hardware encoder brings up the Select Channels For Group Encoder window. Here you'll see all channels available for grouping, and tapping the channel icons you'd like to include adds them to the Group, which can then be named. A useful tip is to group all four effects returns so that they can be turned down or muted in a single operation. This is particularly useful if you have tied up both footswitch jacks for some other purpose and so can't use them for effects bypass.

Setting The Scene

As with most digital mixers, you can store and recall multiple I/O Setups, Scenes and Channel Presets, after which making live adjustments to levels and so on is very straightforward. The mixer can store a virtually unlimited number of these to memory, and they can also be backed up to a USB stick.

Scenes are essentially complete setups, including all fader values, effect types and so on. These may be saved and recalled either in the Settings page, or from the Scenes button at the top left of the Perform screen.


  • Clever and intuitive graphical operating environment.
  • Comprehensive processing with either simple or deep editing options.
  • Full integration with Line 6 StageSource speakers.
  • Feedback suppression included.


  • Costly for smaller bands.
  • No channel expansion option.


The M20D makes great strides in terms of putting heavy-duty mixing power in the hands of musicians, and in a form that they can control without having an in-depth knowledge of mixing and processing.


£1899.99 including VAT.

Line 6 Europe +44 (0)1788 566566.


Line 6 +1 818 575 3600.