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M Audio Delta 66

Soundcard & Omni I/O Front End By Martin Walker
Published January 2001

Both the Delta 66 and Delta 44 soundcards are available either with their standard breakout box, or as a bundle with the Omni I/O front end. This is the Delta 66/Omni I/O bundle.Both the Delta 66 and Delta 44 soundcards are available either with their standard breakout box, or as a bundle with the Omni I/O front end. This is the Delta 66/Omni I/O bundle.

M Audio's Omni I/O interface allows 'Delta card' users to add mic amps, instrument inputs, insert points and monitoring capabilities to their existing systems. Martin Walker gets connected.

Recently, I've reviewed a variety of soundcard‑based products for those who want an all‑in‑one solution that incorporates inputs for the direct connection of mics and guitars. These include the Aardvark Direct Pro 24/96, Echo Mona and Seasound Solo Ex (reviewed in SOS April 2000, October 2000, and December 2000 respectively). There's clearly a demand for such products, but rather than launch something exactly like these, M Audio have used a little lateral thinking and come up with a rather different solution, consisting of an interface that adds these features to a traditional soundcard. Those who don't need them can, of course, just buy the soundcard.

Their Omni I/O is a record/playback 'front end' that interfaces with the Delta 66 or Delta 44 soundcards, adding many extra options including mic/instrument preamps, inserts, effect sends and returns, and headphone outputs. The Delta 44 provides four analogue inputs and four analogue outputs, just like the earlier and very popular DMan 2044 soundcard, but this time with 24‑bit/96kHz capability. The Delta 66 has exactly the same analogue I/O, but adds a co‑axial S/PDIF digital In and Out. Both cards have onboard converters, and are supplied with breakout boxes holding eight quarter‑inch jack sockets for the analogue I/O.

The Omni I/O itself is a half‑width rackmount case containing the extra preamp circuitry and other features, and simply plugs into your Delta card in place of the breakout box. This means that the many existing owners of Delta 44 and 66 soundcards can now add these desirable extra features without having to change their soundcard, while new customers buying both the Omni and Delta 44 or Delta 66 as a bundle save a little money, since they don't need to buy the original breakout box. For the purposes of this review, M Audio sent me the full Delta 66 package (ie. including the breakout box) along with a separate Omni, which made it easy to test the performance in both configurations.

Delta Overview

Although the Control Panel utility for the Delta 66 looks exactly like that of the Delta 1010, the contents of the monitor mixer change to reflect the differing I/O channels. Notice that the installed hardware is detected automatically.Although the Control Panel utility for the Delta 66 looks exactly like that of the Delta 1010, the contents of the monitor mixer change to reflect the differing I/O channels. Notice that the installed hardware is detected automatically.

The Delta 44 and 66 PCI expansion cards are both just five centimetres long. Their backplates contain a 15‑way D‑type connector to attach either the Omni I/O or the standard breakout box. The only difference between the two cards is that the 66 carries gold‑flashed phono connectors for S/PDIF digital In and Out on the backplate, and additional circuitry for the digital interface on the card itself. The four A‑D and D‑A converters are provided by two AKM AK4524 codec chips, as also used by the Aardvark Direct Pro 24/96, Terratec EWS88MT, and Creamware Powersampler among others.

The Delta breakout box is a neat metal enclosure sprayed silver with black legends, and measures 15cm wide, 2.5cm high, and 7cm deep. Despite its small size, it looks sturdy enough to survive being accidentally run over by a small car. It has a single 15‑way socket on the back, and eight quarter‑inch jack sockets along the front for the analogue I/O. With four rubber feet on the base, it's obviously designed to sit either on the desk or somewhere near your computer, though it could also be mounted in a universal rackmount tray using the 5mm screw mounting hole in the bottom of the case. Sadly, though, the supplied umbilical cable is a rather ungenerous 0.9 metres long, and the breakout box wouldn't reach the desktop from my floor‑mounted tower system. M Audio are apparently planning to double the length of the supplied cables, which should make things a lot easier.

Omni Directions

Compared with the Delta 1010, the Hardware Settings page has additional software‑switched signal level options, and a new 'Multiple Card Sync' option (greyed out here) is available to the entire Delta range.Compared with the Delta 1010, the Hardware Settings page has additional software‑switched signal level options, and a new 'Multiple Card Sync' option (greyed out here) is available to the entire Delta range.

The Omni I/O box is altogether grander than the standard breakout box, and also significantly bigger to accommodate its large array of sockets, rotary controls, and push‑button switches. Its dimensions are 21.5cm wide, 14cm deep, and just over 4cm high. This makes it half‑rack width, and again a 5mm screw mounting hole is provided on the bottom plate to bolt it into a universal rackmount tray if required.

Essentially, the Omni I/O's functions are to add preamps to Delta's analogue inputs 1 and 2, and to route the four Delta 66 outputs through many of the other functions found on a small mixer. However, there are just so many controls (nine knobs, six switches, 10 LEDs, and a total of 24 sockets) crammed onto the front and rear panels that it took me quite some time to sort out what exactly was on offer. This was partly due to the rather cryptic manual and signal‑flow charts which, although they contain all the information, seem to place it in rather a convoluted order.

Analogue Input 1 and Input 2 each have a high‑quality preamp — apparently the mic preamp circuitry used is identical to that in M Audio's rather more upmarket DMP2 — and these inputs are intended for either mic or instrument signals, using a Neutrik Combi socket. If you plug in a male XLR plug you get a low‑impedance balanced input suitable for a mic, with 48 Volt phantom power globally switched in and out from the rear panel (although, sensibly, its red LED indicator is on the front panel). Plugging in a quarter‑inch jack gives you a high‑impedance unbalanced input that should prove ideal for electric guitars or acoustic guitars with pickups.

Next in each preamp signal chain is a switchable pad to cope with hot signals, which reduces the gain of whichever input is in use by 20dB. This is followed by a rotary gain control, and then two level indicators — a green LED to show that a signal is present, and a red one that flashes when the signal level is 2dB below clipping. Following this are TRS‑wired insert points on the back panel which, like all the remaining sockets on the Omni I/O, are on standard quarter‑inch jacks. Inputs 3 and 4 are at line level on the back panel, and have no preamp or insert features.

Four additional stereo Aux inputs are also provided on the back panel, and are TRS‑wired to carry both the left‑ and right‑channel signals from line‑level sources such as MIDI synths. To save you wiring up special cables you could use commercial 'insert' cables with twin mono jacks at one end and a single stereo plug at the other. All four of these Aux inputs are normally routed to the main stereo output buss (more on this in a moment), but two rear‑panel switches let you instead route stereo Aux 1 directly to the Delta H/W Inputs 1 and 2, and stereo Aux 2 directly to the Delta H/W Inputs 3 and 4.

Omni Outputs

The Delta 44 card: the same 4‑in, 4‑out analogue breakout box is standard with the Delta 66.The Delta 44 card: the same 4‑in, 4‑out analogue breakout box is standard with the Delta 66.

There are quite a few outputs on offer as well. The four Delta H/W Outs are wired directly to four balanced/unbalanced Direct Outs. In addition, each of these four playback channels has its own front‑panel rotary Effects Send control. These feed a single mono balanced/unbalanced 'FX Send' TRS‑wired socket on the rear panel. A pair of rear‑panel sockets provides left and right effects return facilities, so that you can add reverb or other effects in differing amounts to each playback channel. This return is connected to the stereo mix buss.

The output from this stereo buss is available from a pair of balanced/unbalanced sockets on the rear panel labelled 'Record (Mix) Outs', along with two pairs of front‑panel LEDs showing Signal present and Clip for each channel. These outputs would typically be used to feed a DAT or Minidisc recorder during final mixdown. A further pair of rear‑panel monitor outputs also has a rotary Monitor level control on the front panel, and there are two headphone outputs on the front panel, each with its own rotary level control. The remaining controls are a front‑panel power switch with red LED indicator, and the rear‑panel sockets to attach the Delta soundcard and supplied 9 Volt AC adaptor.


M Audio Delta 66

M Audio supply Mac and PC drivers for all their MIDI and Audio products on a single dual‑format CD‑ROM, along with manuals and other reference material in PDF format. For the PC, drivers are provided for Windows 95/98, Windows NT 3.51/4.0 and Windows 2000. The same set of driver files is used for the entire Delta range (Delta 44 and 66, DiO 2496, and Delta 1010), and the Windows 95/98 ones on my CD‑ROM were version As usual, my first port of call before installation was the Midiman web site, where I checked to see if any newer drivers had been released. Sure enough, I was able to download version for Windows 95/98, while Windows ME/2000 WDM Beta drivers are now also available. Various new features have been added to the Delta drivers since I reviewed the Delta 1010 that give all Delta owners more flexibility. For instance, the PC drivers are now GSIF‑compatible, which will please users of Nemesys products such as Gigasampler and Gigastudio. Sadly, though, you still have to reboot Cubase after making any changes in the driver settings for these changes to take effect.

Driver installation on my PC was uneventful, with Windows correctly detecting the new Plug and Play hardware, and when I arrived back at the desktop I not only had a correctly functioning soundcard, but also an extra 'M Audio Delta H/W' applet in my Control Panel. Mac owners can drag their Control Panel file from the CD‑ROM to any partition and drive, and for quick‑launch convenience both PC and Mac owners can create a shortcut or alias from the desktop.

Control And Monitoring

The M Audio Delta Control Panel utility is a standard feature across all of the Delta range, though a number of new options have been added since I reviewed the Delta 1010 a year ago. For use with MME‑based applications on the PC you can launch it as a stand‑alone utility, but for those that use ASIO or EASI drivers it's better launched from within your music application, since this will directly control some functions such as clock settings and sample rate. The I/O features that can be accessed from it will depend on which card you have installed. In the case of the Delta 66, the outputs appear as WavOut 1/2 Delta‑66, WavOut 3/4 Delta‑66 and WavOut S/PDIF Delta‑66, while the inputs appear as PCM In 1/2 Delta‑66, PCM In 3/4 Delta‑66 and S/PDIF In Delta‑66, along with a fourth one, Mon. Mixer Delta‑66, the purpose of which will become clear shortly.

The utility has five tabbed pages labelled Monitor Mixer, Patchbay/Router, Hardware Settings, S/PDIF, and About. The latter is self‑explanatory, giving the driver and panel version numbers. Monitor Mixer provides a flexible way to create your own mix of the three stereo WavOut playback signals, along with any input signals appearing at the three stereo H/W (hardware) inputs. Each of these 12 possible mono signals has its own 24‑bit fader with useful position readout in dBs, a peak‑reading meter, Pan slider, Mute and Solo tick boxes, along with one Stereo Gang tick box per pair. The control panel is only long enough to display four stereo pairs side by side, but a scrollbar lets you move through the rest. An overall Master Volume section provides similar facilities, with a pair of faders and meters, along with a single Mute and Stereo Gang tick box.

The output of the Monitor Mixer can be directly routed to either the H/W Out 1/2 or H/W Out S/PDIF using the Patchbay/Router page, so that you can hear its signals with zero latency, and if you wish to record this combined signal you can select the Mon. Mixer Delta‑66 mentioned in the previous section as an input in your music application. In the case of the Delta 66, only three of the five displayed columns of the PatchBay/Router are used (H/W Out 1/2, H/W Out 3/4, and H/W Out S/PDIF), the rest being greyed out. The signal arriving at the H/W Out 1/2 sockets defaults to the WavOut 1/2 signal for normal playback duties, that at the H/W Out 3/4 to WavOut 3/4, and the H/W Out S/PDIF to WavOut S/PDIF, but various other options are available for each one. H/W Out 1/2 can instead receive the combined output from the Monitor Mixer as just mentioned, or the signals from the S/PDIF input, the S/PDIF input with stereo channels reversed (a new addition since I reviewed the Delta 1010), or either of the H/W In 1/2 and H/W In 3/4 analogue input pairs. The H/W Out S/PDIF has identical options, while the H/W Out S/PDIF is the same apart from the Monitor Mixer option.

The third tabbed page is Hardware, which controls the clock and sample rate settings, along with various options for driver buffer and sync, as well as some additional settings that don't appear with the Delta 1010. The panel is divided into six areas. At top left is Master Clock, with options for Internal Xtal when the card is in master mode, and S/PDIF In when in slave mode. Beneath the two radio button options is a text box that displays Locked or Unlocked to indicate whether a valid clock signal is currently available.

Codec Sample Rate has 12 radio buttons for the available sample rates from 8kHz to 96kHz, and normally displays the current sample rate. If the Internal clock is being used, this will be set by your software application when it plays back an audio file. There are two additional options. You can tick 'Rate Locked' and select a specific codec sample rate if you want to prevent your application from changing it, which is useful if, for instance, you accidentally load in a 22kHz file but don't want your sequencer's setting to get changed from 44.1kHz. 'Reset Rate When Idle' lets you return to your chosen sample rate when your software isn't actively forcing a setting, which is useful if you want to keep the monitor mixer running at a specific sample rate. If you select 'S/PDIF In' for the master clock, the S/PDIF Sample Rate radio buttons let you select the rate expected at this input, and you need to set your music application to the same rate to avoid an error message.

A whole new area labelled Variable Signal Levels provides three software‑switched options allowing input and output sensitivity to be chosen from +4dBu, Consumer, and ‑10dBV. The analogue outputs have a global three‑way level option, while each of the four analogue inputs can be switched individually. Although most consumer audio products normally provide ‑10dBV output levels and input sensitivity, the manual confusingly describes the Consumer setting as suitable for semi‑pro equipment, though it's actually an intermediate setting with 6dB more headroom.

The DMA Buffer Sizes panel lets you adjust the Wave and ASIO driver latencies separately, and the latest drivers now also support Emagic's EASI protocol alongside ASIO. Available settings range from 8mS to 28mS for the Wave driver, defaulting to 20mS, while the ASIO/EASI drivers display the number of samples per buffer, from 336 to the default 2688, giving latency values of 8mS and 61mS respectively at a sample rate of 44.1kHz.

The final panel in the Hardware Settings page is Multitrack Driver Devices, where you can select either 'Single and In‑Sync' or 'Independent'. The first option should be employed when you intend to use all the inputs and outputs with one multitrack application, and the second if you want to split some off for a second one such as a soft synth. A new third option has appeared since my Delta 1010 review labelled 'Multiple Card Sync'. This allows you to run up to four mixed Delta cards simultaneously, although they are not sample‑locked.

The right‑hand section of the Control Panel is always visible whichever of the five tabbed pages is selected, and four radio buttons here display the full list of detected Delta hardware. Above them are Save, Delete, and Load buttons to store and retrieve different sets of Control Panel settings.

The final page is labelled S/PDIF. Here the Digital Input status is displayed either as 'Invalid or Not Present' or 'Valid Input Detected', and you can switch between professional and consumer flag settings for the Digital Output Format: the electrical levels remain the same, but some AES‑EBU gear may recognise this 'professional' format even at the lower S/PDIF levels. If you tick the 'Advanced Settings' box a further set of options appears. When in Consumer mode you can set SCMS off, Copy Permitted, or 1st Generation (which prevents copying from copies). If your DAT machine uses pre‑emphasis during recording, you can also enable the 50/15mS Emphasis flag on the digital output signal. When in Professional mode these options change to Audio/Non‑Audio (a setting which is mostly ignored by other gear), while the Emphasis has a third CCITT setting.

In Use

The Delta 66's D‑A converters showed subtle improvements over those of my own benchmark Echo Gina card, with a greater sense of space, depth, and realism during acoustic performances. To measure the A‑D noise levels I chose the lower input sensitivity of +4dBV. Using Wavelab my RMS background noise tests initially proved disappointing, with figures around ‑84 to ‑85dB whatever the bit depth and sample rate, until I noticed that I had been measuring a brief jump in noise levels at the start of each recording.

Examining the files more closely showed an initial half‑second noise surge, followed by much lower levels for the remainder of each recording. This is no doubt due to some initialisation process, and won't affect real‑life recording except perhaps during some drop‑ins (though the surge is too low in level to be noticeable in most mixes). The measured noise figures were a lot more encouraging when I ignored this anomaly, providing a fairly typical ‑93.1dB during 16‑bit/44.1kHz recordings, dropping to ‑98.5dB with 24‑bit/44.1kHz recordings. Opening out the bandwidth to 96kHz caused this to rise slightly to ‑97.2dB. These figures are in line with M Audio's own published spec, which claims a 99dB A‑weighted dynamic range for the A‑D converter, and are fairly typical when compared with most other products using AK4524 chips.

As with the Delta 1010, I managed to run the ASIO drivers at the lowest setting of 336 bytes per buffer, giving me a latency of 8 milliseconds at 44.1kHz with my Pentium II 450MHz PC. However, unlike the Delta 1010, I couldn't get the Delta 66 S/PDIF I/O to produce bit‑for‑bit copies when I sent a recording to and from a DAT recorder, but the difference was only one bit's worth of dither noise, which shouldn't bother most people. As expected, changing the Delta 66 breakout box for the Omni didn't change the noise figures at all for inputs 3 and 4, and although the mic/guitar preamps of course added a little noise of their own to inputs 1 and 2, they sounded very nice indeed.

However, as mentioned earlier, it did take me some time to fully get my head round the Omni options, largely due to the inclusion of such a large number of controls in such a small area. The Omni would have looked far more impressive with a full rack‑width case, but I suspect that this would have pushed up the price too much. As it is, £229 is a bargain for a mixer with two mic/guitar preamps and two line inputs, along with four stereo inputs and four soundcard output channels during playback, complete with a simple effect send/return system.

The Omni is also more versatile than it at first appears. The 12 playback channels could be augmented by the signals at the four input sockets, if you premix them using the M Audio Control Panel monitor mixer, to provide a total of 16 signals during mixdown to an external DAT recorder. Although you might normally use the effect sends and return during mixdown, by rerouting the effect return cables to inputs 3 and 4, you could also use them to record mic/guitar signals complete with outboard effects. Yet another application is keyboard submixing, which could be achieved by routing the Record Outs to inputs 3 and 4 to bounce up to four stereo signals down to one stereo track.

Final Thoughts

Once again, M Audio/Midiman have managed to come up with products that have a rather different slant from those of their competitors. For musicians who don't need the eight ins and outs of the majority of multitrack soundcards, the Delta 66 is still a useful step up from traditional stereo cards. Its 4‑in/4‑out format is ideal for the occasional recording of small ensembles, and even a basic drum kit, while for the mainly electronic musician it's perfect to run a MIDI + Audio sequencer alongside Gigasampler or another stand‑alone soft synth/sampler. Of course, the audio performance isn't quite in the same league as the Delta 1010, but then neither is the price — on the street you can already find the Delta 66 at under £300.

Once you add the Omni I/O at a typical street price of £190 (and I'm sure many existing owners of the Delta 44 and 66 will do just that), it answers the prayers of those who want to record vocals or guitars but who haven't got a suitable hardware mixer or voice channel. M Audio have really crammed a lot of features into a small space, and once you get your head around the options it's surprisingly versatile. For those with other soundcards who are looking enviously at the Omni, help will soon be at hand. In a month or two after this review appears, we should see the release of an optional breakout cable for the four analogue ins and outs that normally interface with the Delta card, so that you can connect the Omni to any soundcard.

Overall, the Delta 66/Omni bundle is ideal for the musician who wants to record using a few mics and instruments who doesn't want to compromise on sound quality, but who doesn't have loads of cash. It may be a little cramped but it's excellent value at a bundled price of £548, and I'm confident that M Audio will sell bucketloads.

Brief Specifications


  • Analogue connectors: balanced/unbalanced TRS quarter‑inch jack sockets.
  • Analogue inputs: four, software‑switched +4dBu/Consumer/‑10dBV sensitivity.
  • Analogue outputs: four, software‑switched +4dBu/Consumer/‑10dBV sensitivity.
  • Peak input and output signal: +14dBu at +4dBu, +6dBV at Consumer level, +0dBV at ‑10dBV settings.
  • A‑D converters: 24‑bit, 64x oversampling.
  • Input dynamic range: 99dB (A‑weighted).
  • Input impedance: 10kΩ minimum.
  • D‑A converters: 24‑bit, 128x oversampling.
  • Output dynamic range: 103dB (A‑weighted).
  • Total harmonic distortion: <0.0024 percent (A‑D), <0.0015 percent (D‑A).
  • Frequency response: 22Hz to 22kHz, +0.3/‑0.2dB.
  • Supported bit depths: 8, 16, and 24.
  • S/PDIF: up to 24‑bit/96kHz operation supported.
  • Internal sample clock: 8, 9.6, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48, 88.2, and 96kHz.
  • S/PDIF sample clock: 32, 44.1, 48, 88.2, and 96kHz.


  • Inputs: two, switched mic or instrument using Neutrik Combi socket, balanced/unbalanced, with insert points.
  • Mic inputs: up to 66dB gain, low impedance, globally switched 48 Volt phantom power.
  • Instrument inputs: up to 46dB gain, high impedance.
  • Frequency Response: 10Hz to 200kHz.
  • THD: 0.0009 percent.
  • Dynamic range: 130dB.


  • Inputs: 4 stereo aux (1 & 2 switchable to soundcard inputs), stereo effects return.
  • Effects send: one mono send per Delta playback channel.
  • Outputs: four direct outs from soundcard, mono effects send, stereo record out, stereo monitor out, two headphone outs.


Alternative systems offering the same facilities as the Delta 66/Omni I/O bundle in the same price bracket are thin on the ground. The Aardvark Direct Pro 24/96 has four mic/line inputs and four outputs, but the digital I/O replaces two of each of these when used, although it does have built‑in DSP effects for its rather more expensive £649. The Echo Mona has four ins and six outs, but the addition of its ADAT interface and impressive rackmount case pushes its price much higher to £799. The SeaSound Solo Ex for £599 also has a very attractive rackmount case, two mic/guitar inputs, two line inputs, and similar monitoring facilities, but can only record in stereo.


  • High audio quality for both soundcard and mic preamps.
  • Excellent value for money.
  • Omni offers very flexible routing options.


  • Omni functions are initially confusing.
  • The Omni manual doesn't help much.
  • Umbilical cable on review model was too short.


The Delta 66 provides a useful combination of features at an attractive price, and should suit plenty of musicians, while adding the Omni could turn it into the nerve centre of a small studio using a couple of mics, guitars, and up to four stereo keyboards.