TASCAM DM24

Tascam DM24 Digital Mixing Console

Published in SOS March 2002
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Reviews : Mixer

Digital Mixing Console

Tascam's affordable new 32-channel, eight-buss digital mixer takes on Yamaha's O-series, providing 24-bit/96kHz operation, surround panning, and effects processing from TC Works and Antares.


Hugh Robjohns

Virtually every console company, regardless of market position, has at least one digital mixer in their product portfolio these days, the cheapest models costing well under a thousand pounds and the most expensive... well, you'll get small change from a million! Tascam's latest addition to the market is the attractively priced DM24, a late entry to the fray which benefits from Tascam observing the development of its competition.

Since Yamaha have, by and large, set the standards in the mid-price digital console arena, it might be useful to reference the DM24 against the equivalent O-series desk. In terms of list prices you should therefo

  Test Spec  
  Tascam DM24 OS v1.11  
re be thinking in terms of the O3D, but the complement of I/O, feature set and functionality of the DM24 places it closer to the legendary O2R. After all, this is a 32-channel, eight-buss console intended for 24-track digital recording, and comes complete with internal dual stereo effects. Tascam have priced the DM24 to be attractive to project studios, yet it's feature set and control surface will appeal to many professionals too.

Feature Set

The DM24's styling and operational approach borrow heavily from Yamaha's paradigm,

Tascam DM24 £2499
pros
Generous number of mic preamps.
96kHz sample rate capability.
Control-surface ergonomics.
Flexible automation system.
Seamless integration with DTRS and MX2424 recorders.
A lot of desk in a small footprint
cons
Limited onboard metering.
Multitrack return routing is convoluted.
No dedicated surround monitoring outputs
Few analogue outputs.
summary
A cost-effective but well-specified digital mixer with a wide range of professional features and facilities. Music and post-pro multitrack applications will benefit from sixteen decent mic preamps and excellent integration with DTRS recorders, but minimal analogue outputs will limit versatility in other environments.

complete with a central monochrome LCD screen -- although the operation is sufficiently different to cause confusion if you're familiar with the Yamaha desks! The desk provides 32 input channels (linkable for stereo), routing to eight mix busses plus a stereo main output. Post-fade channel direct outs can also be used for multitrack recording. There are six auxiliary sends, linkable for stereo, and two internal stereo multi-effects processors providing Antares mic and speaker modelling, TC Works reverbs, and a miscellany of other generic effects. Each channel supports mixing in a variety of surround formats, and is equipped with four-band parametric EQ (with libraries), delay, compression (switchable pre- or post-EQ) and expander/gate. This last is only available on the first 16 channels, and there is no provision to key one channel with the signal from another in the current software. The 16 long-throw, motorised faders control the channel and master paths through three fader layers, and there are integral snapshot and dynamic automation facilities.

The desk is equipped with 16 good-quality analogue mic/line inputs, capable of 24-bit resolution and 96kHz sampling rates -- a feature unavailable in Yamaha's O-series consoles, and only recently introduced with their new DM2000 mixer. The XLR mic inputs and TRS jack sockets for line inputs are effectively wired in parallel, so only one connector can be plugged in at a time. Each input also has an unbalanced insert point on another TRS socket, and the phantom power is switched to the XLRs in blocks of four. There are few analogue outputs: control room and studio stereo monitoring, a main stereo output (on XLRs) with unbalanced inserts, and four sets of 'floating' sends and returns on more TRS sockets. These sends and returns can be used either as assignable insert points, or as effect send/return connections. There is also an unbalanced two-track stereo return to the monitoring section.

On the digital side of things, there are 24 channels of TDIF I/O, eight channels of ADAT optical digital I/O, two stereo digital inputs (independently switchable between AES-EBU and S/PDIF connectors, with sample rate conversion if required) and two stereo digital outputs (feeding both AES-EBU and S/PDIF sockets simultaneously, the shared data format being selectable). The bit resolution of these outputs can be specified in software.

Added to this impressive array are two slots for optional eight-channel interface cards (see 'Optional Interface Cards' box for details). Needless to say, not all these inputs can be used at the same time -- if inputs are required from the first slot card then the first eight TDIF inputs cannot be used. Likewise with slot two and the second bank of TDIF inputs,

  MIDI Control  
  Channel faders, mutes and pans can generate MIDI channel and controller data to operate external devices, or external devices can control these same mixer parameters over MIDI. There are eight fader layers available purely for the purposes of MIDI control, and these can be set up so that each of the 16 faders in a given layer generates the same controller number, but transmits it on its own individual MIDI channel.  
as well as with the ADAT ports and the third bank of TDIF inputs. Routing the physical inputs and outputs to and from the internal DSP mixer is performed via the mixer's graphical user interface.

The familiar trio of MIDI connections is provided, and the desk reacts to all the usual MIDI control messages, as well as being able to generate MIDI data from the faders and switches to control an external DAW, for example. Both word clock and timecode synchronisation are available, with word clock I/O on BNCs, and SMPTE timecode via a phono socket. Remote control facilities include the aforementioned MIDI (MMC and MTC), plus RS422 (Sony P2 protocol), eight GPI contacts, and a dedicated DTRS-format remote control port.

Naturally, the built-in digital I/O and control interfacing favours Tascam's own digital recorders -- machines such as the DA88/38, DA98/78HR, and MX2424. However, plenty of other digital equipment can be interfaced successfully, either through the integral TDIF interfaces, or by installing the optional interface cards -- to provide 24 channels of ADAT lightpipe, for example. Inevitably, the either/or switching arrangement between TDIF ports and slot cards restricts the possible I/O combinations, but should not cause too many frustrations in practice.

The desk incorporates a talkback system, with studio and slate destinations, as well as comprehensive control-room monitoring, with selectors for the main stereo output plus three programmable sources. Adjustable dim and mono facilities are included along with a volume knob (but no balance control), but there is no support for surround monitoring. The studio monitoring source selector and volume control are located on a menu

page. The stereo meters on the mixer proper follow the monitoring selection, and channel metering is normally only available through the LCD. However, an optional meterbridge can be connected to provide LED bar-graphs for 24 channels with bank switching to view the remaining desk channels. A dedicated stereo output meter is also included along with a large timecode display, so it is a very worthwhile addition.

Delving Into The Software

Whereas Yamaha have the engineering capacity to develop their own DSP chips, Tascam have chosen to employ off-the-shelf floating-point SHARC DSPs using system software developed by a dedicated team in California. The result is an operating system which is as easy (or convoluted) to use as most other digital consoles of this ilk, but with more differences than similarities compared with the Yamaha O-series approach. The traditional diamond of cursor buttons with Enter key and Jog/Data wheel provide the tools required to navigate the screen menus, and a set of four rotary encoders and associated buttons allow quick adjustment of selected parameters. This aspect of the console's operating system is very intuitive and pretty fast to use.

Buttons to the right of the screen provide direct access to various control and configuration menus, most buttons having dual functions accessed via a Shift key. The majority of menus have two or three pages of sub-functions, but they are laid out clearly and logically. Through these menus the console can be set up to control other machines, receive or generate MIDI, determine word clock sources and rates, allocate the I/O, program the monitoring sources, manage the libraries and automation systems, and control the internal effects processors.

The patchbay screens are intuitive and allow any of the 32 channels to receive any of the sixteen analogue mic/line inputs, four assignable returns, either channel of the two stereo digital inputs, or either channel of the two stereo internal effects processors. In addition, channels 1-24 can also access the multitrack returns (in fixed blocks of eight) from the TDIF, ADAT or option card slots, as appropriate.

To the left of the LCD screen are assignable channel controls which operate on the channel currently selected (either by pressing its Sel button, or by touching its fader). Six buttons set the mix-buss, stereo and direct-output routing, while five more determine which EQ bands are controlled by the encoder knobs just below. These knobs normally adjust EQ gain, frequency and bandwidth (according to the EQ filter mode), while a fourth controls the pan or stereo balance. All four of these knobs can also be assigned to set the aux send levels, or control the gain of each of the four EQ bands simultaneously. All channel facilities, including delay and dynamics, can also be adjusted using the soft knobs and buttons below the screen.

Although there are six auxiliary busses, there are no dedicated physical aux outputs. Instead, each auxiliary must be allocated to a specific destination -- such as the two internal effects processors, the AES-EBU and S/PDIF outputs (in pairs), or any of the four assignable analogue sends. This last option is much like the Omni ou

tputs found on Yamaha's O1V mixer, and in conjunction with the four associated returns, enables external signal processing to be introduced into any desired signal path within the mixer. Processed signals from outboard effects can also be routed back to the desk through either of the two AES-EBU or S/PDIF inputs.

The fader bank switching, remote transport facilities, and automation controls are all located in the bottom right-hand corner at the front of the desk. I often seemed to press the stop or play buttons with my arm when using the cursor buttons or jog wheel, but this was probably because the desk was too high on my desktop, so it may not worry too many end users...

Multitrack Monitoring

Tascam say the desk is optimised for 24-track recording, and it can certainly accommodate the outputs of a 24-track machine. However, because this is not an in-line desk and does not have 24 dedicated monitor returns, the monitoring arrangements are a little unusual.

Most users may well only need to record a few tracks simultaneously, and in these cases the easy solution is to assign the first eight mic/line inputs to channels 25-32 and route them to the multitrack via the eight m

  Running The DM24 At 96kHz  
  Operating the DM24 at high sample rates obviously doubles the DSP workload, and the console's resources are broadly halved as a result. Consequently, at 96kHz sample rates, the DM24 becomes a 16-channel console with 12 channels retaining the ability to accommodate multitrack returns. The complement and functionality of signal processing in each channel remains the same as at standard sample rates.

On the output side, all eight multitrack busses are retained, preserving the ability to create 5.1 surround mixes, but there are only four aux busses. Only one set of stereo digital I/O is available (configurable for either double-speed, single-wire, or half-speed, dual-wire connections), with just two assignable analogue sends/returns, and only the first eight channels are equipped with gates.

The digital I/O routing is configured such that the first TDIF port accesses multitrack busses 1-4, direct outs 1-4, or auxes 1-4; the second TDIF port provides busses 5-8, direct outs 5-8 or auxes 1-4; and the third TDIF port can be switched between either of these two configurations, as required.

 
ix busses in the usual way. The multitrack returns can then be assigned permanently to channels 1-24 (the only channels which can access the multitrack returns) for monitoring and mixing direct to the stereo output. All fairly straightforward.

However, if it is necessary to record more than eight tracks simultaneously, the situation becomes more complex. For example, recording 16 tracks simultaneously requires sixteen channels to control the analogue inputs and route them to the digital multitrack. As channels 25-32 can't be used for monitoring the multitrack, it would make sense to allocate these to the control eight mic/line inputs, perhaps with 17-24 handling the other eight. That leaves channels 1-16 to monitor the returns, which is fine... but how could you handle monitoring from a 24-track machine?

Tascam offer two solutions, the simplest being to derive direct outputs from each mic preamp using the unbalanced insert, and to connect them straight to the corresponding inputs of the multitrack machine. The returns can then be brought back into channels 1-24 for mixing and monitoring. This makes 16-track simultaneous recording easy, but requires special cables running unbalanced signals, and affords no signal processing prior to recording. Desk inputs can be routed to the remaining eight tracks of the recorder through the mix busses in the conventional way.

The other option employs an unusual software feature of the DM24 in which the first two aux busses are used as a monitor mix, leaving the rest of the channel facilities available for handling and routing inputs to the multitrack in the normal way. The two aux busses have to be linked for stereo (providing level and pan controls) and switched to take their source from the multitrack return pre-assigned to the corresponding channel, instead of pre- or post-fader in the channel. Confusingly, this mode is only available on the first 16 channels. Channels 17-24 are configured to take their inputs directly from the relevant multitrack returns, so the relevant aux busses must here use the pre-fader signal to contribute the appropriate monitoring feed.

The control room monitoring obviously needs to be switched to monitor the first two aux busses, but Tascam have thoughtfully set up a default snapshot to

  The DM24's Automation  
  The DM24 features a full snapshot and dynamic automation system with quarter-frame accuracy and control over faders, mutes, EQ, aux sends, dynamics, library recalls, and surround panning. A number of factory snapshots are provided to configure the desk in default recording and mixing modes, either at standard or doubled sample rates. These are intended for 24-bit, 24-track recording via the TDIF ports, with 16-bit stereo mastering -- ideal for a system incorporating an MX2424 hard disk multitrack with a DAT or CD-R master recorder, for example. However, alternative configurations can be set up to suit other equipment combinations. The current firmware only supports slaving of the automation to external SMPTE or MTC timecode (all standard rates), although it is planned to introduce an internal MTC generator for stand-alone operations.

Up to 64,000 automation events can be stored internally in eight memory banks, with up to 32,000 allocated to one mix (some mix!). Automation data (along with library files and snapshots) can be saved and recalled as a SysEx dump via MIDI to a data filer or sequencer.

Using the automation is very straightforward, with all parameters being stored initially as a 'static' position until adjusted, at which time the dynamic information is written to the automation pass. The faders are touch sensitive and therefore drop in and out of write mode as they are touched and released; the other controls drop in when moved, and drop out after a predetermined time of inactivity. All the familiar automation facilities are available including a trim mode, write to end, timed revert, rehearse and so forth. There is even a multi-pass mode to remove the frustration of having to re-arm the automation for writing each time the timecode stops as the multitrack returns to the start of the track.

 
configure the desk in this way. As the aux send levels can be controlled by the faders via the relevant fader page, building a monitor mix on the aux busses actually works quite well -- almost like an in-line desk in some ways. The two aux busses can also be used as a cue mix for artists in the studio, or recorded via the stereo digital outputs or assignable sends. This probably sounds rather complicated, and a dedicated 24-track monitor mix system would have made life infinitely easier, but it all works adequately in practice.

Surround Mixing

The DM24 can accommodate 5.1 surround mixing via the eight busses, and the channel panning mode can be configured for stereo, quad, LCRS, or 5.1. The various channels can also be allocated to recorder tracks in a variety of ways to accommodate specific house track standards, including the approved AES 5.1 channel format.

The channel's overview screen display only ever shows the left-right pan position -- surround panning has to be viewed on a dedicated menu page. Controls are available here for left/right and front/rear panning (both with divergence settings), plus a fifth knob to move the sound source diagonally (either along the front-left to rear-right, or the front-right to rear-left axes), essentially saving the effort of having to turn the two orthogonal panners simultaneously. The contribution to the subwoofer can also be adjusted.

The DM24 is not equipped with surround monitoring facilities, and the handbook recommends installing the optional analogue interface card to output the surround busses to an external surround monitoring controller.

Internal Effects

There are two dedicated internal effects channels and two processing engines. The first engine contains the TC Works reverb and Antares mic and speaker modelling algorithms, only one being usable at a time. The second engine contains Tascam's own general-purpose time-domain, dynamics and distortion algorithms. Either engine can be allocated to either effects channel, or they can be placed in series if required (allowing phased or chorused reverbs, for example).

The two effects channels can be configured to operate either as conventional send/return loops, with inputs and outputs routed via any of the aux sends and channel returns, or as inserts to specific channels or mix busses. The processors

  Optional Interface Cards  
  Tascam's conventional offerings include the IFAD/DM (ADAT), IFAE/DM (AES-EBU), IFAN/DM (analogue), and IFCS/DM (cascade) interfaces. All are bi-directional eight-channel devices employing 25-pin D-Sub connectors, except the ADAT card which uses Toslink optical connectors.

To work with 24 channels of ADAT data, both interface slots have to be fitted with IFAD/DM cards, providing a further sixteen ADAT I/O channels to augment the eight available as standard. Unfortunately, it is not possible to configure the desk to provide 24 channels of AES-EBU interfacing -- the best achievable is 20 channels (16 via two IFAE/DM cards, plus the desk's integral pair of stereo AES-EBU ports).

Adding a pair of IFAN/DM cards will bestow the console with 16 more line inputs to supplement the standard 16 mic/line inputs. However, this would reduce the desk's digital I/O to a single eight-way TDIF or ADAT port, plus the stereo AES-EBU and S/PDIF connections. Although only three specific eight-way input interfaces can be employed at one time, all digital outputs are active simultaneously (ie. the integral TDIF, ADAT, AES-EBU, and S/PDIF outputs, plus both option cards, if installed).

The Cascade card allows two DM24s to be conjoined as master and slave, functioning as one large desk. The aux, multitrack, stereo and solo busses become common to both, and both pairs of internal effects processors become available to any aux. Snapshots and automation are controlled from the master console, but the data is stored locally on each desk, and must be archived and recalled independently. The stereo busses and monitoring of the two consoles can be used independently, allowing multiple stereo mixes to be produced and separate monitoring systems to be controlled. The cascade card also supports 96kHz operation, enabling a pair of consoles to provide a full 96kHz, 24-track digital mixing system.

 
can also be configured for mono or stereo inputs.

There are 99 TC Works reverbs, all very usable and covering a wide range of styles including ambience, box, room, chamber, hall, plate, drum/percussion, tunnel and special effects. A very comprehensive range of program parameters can be edited, although near-ideal pre-programmed reverbs were usually easy to locate. One unusual parameter, though, is the 'space editor' -- altering the notional room shape between large and small cubes, a D-shape, a prism, or a T-shape. This seemed so much more powerful and realistic in creating believable early reflections than the simple early reflections patterns found in many other reverbs.

The Antares modelling algorithms cater for 83 different microphone types and ten loudspeaker types. When inserted into an input channel or output buss, these programs certainly change the sound, and you may well like the results... but modelling can only simulate the on-axis response of a microphone or speaker and really can't produce the quality of a £1000 condenser mic from a £50 dynamic! It can be useful when recording a lone voice in a well-damped acoustic with no off-axis spill to worry about, but this is only an effect, not a miracle.

Tascam's own general purpose effects -- there are 127 of them -- are grouped under headings such as Chorus, Flange, Phase, Delay, Pitch-shift, Exciter, De-esser, Compressor and Distortion. Again, they are mostly usable, if run of the mill, complementing the other effects well and certainly proving effective within mixes.

Conclusion

The DM24 is a powerful and well-equipped mixer, offered for a surprisingly low UK price. While there are some omissions in the current operating software -- lack of key inputs for channel gates, quirky multitrack monitoring arrangements, and no surround monitoring capability -- the desk's 16 mic preamps are refreshingly quiet and accurate, the long-throw faders and elegant automation system are a joy to use, and it sounds pretty good too. The desk is also easy to interface with a wide variety of disparate digital equipment, thanks to its plethora of different interface formats. Overall, a worthy addition to the mid-price digital console market, improving the price/performance ratio significantly.

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