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Korg D4

Digital Multitracker
Published September 2005
By Tom Flint

Korg D4Photo: Mike Cameron

Korg's latest multitracker is as small as it is affordable.

The D4 is a four-track digital recorder with built-in effects, a simple rhythm generator, and some basic audio editing tools. It's a touch smaller than a sheet of A5 paper, no deeper than a cheese sandwich, and about as heavy as a copy of Sound On Sound. As you can imagine, it's pretty compact, although too large to be a pocket device, especially when its external 9V power supply is taken into consideration. In fact the D4 is more of a 'recording notepad', capable of recording basic compositions two tracks at a time, and requiring the minimum of outboard. For example, a guitarist can start by plugging their lead directly into the back, use the in-built tuner to get set up, select a suitable amplifier and speaker simulation, lay on some reverb, delay or distortion, and play along to one of the internal rhythms at a tempo and time signature of choice. The D4's editing tools make it possible to hone a performance somewhat, alternative takes may be stored on the 28 virtual tracks, and there are additional send effects available for use on the mix and across the stereo buss during mixdown. Complete mixes can be saved as stereo MP2 files and imported into a USB-connected PC or Mac, or simply output to a stereo recorder of choice.

Memory Flash

There's no hard drive in the D4 so all recording work is stored on Compact Flash cards. Compact Flash is nowhere near as fragile as a hard-drive assembly, and that makes it an ideal memory format for portable recorders like the D4. To date, the limited capacity of RAM cards has meant that recorders using them have been limited in terms of track count and/or recording resolution. Things are sure to change, however, now that some cards can store up to 2GB of data. To put it into perspective, Roland's VS1680 16-track originally shipped with a 2GB hard drive as standard, and that seemed pretty good at the time!

Having just four tracks, the D4 should be well served by the new large-capacity cards, yet it still uses data compression, and its sample rate is fixed at 32kHz, instead of the CD standard of 44.1kHz. Although these RAM-saving measures make it possible to use cheaper cards, they also compromise recording quality. Nevertheless, the D4 still has 20-bit A-D and D-A converters and records at 16 bits per sample. MPEG1 Layer 2 compression is applied at all times, although there is a per-project choice of three different levels of data compression. Recording time varies according to the severity of the data compression and the capacity of the card, which can be anything from 16MB up to 2GB.

Family Resemblance

Korg D4Photo: Mike Cameron The D4 is a direct descendant of Korg's PXR4 four-track, reviewed in SOS December 2001. The specifications of the two products are very similar, but there are important differences. Firstly, the PXR4 used Smart Media cards, which Korg have abandoned in favour of Compact Flash. The PXR4 was designed to be pocket sized, but I suspect few owners ever carried their one around with the mobile and wallet. Korg have taken a different approach this time and made the D4 larger and less fiddly to operate. One other difference is the origin of the effects. The PXR4 derived its effects from Korg's Pandora processor, whereas the D4 uses the slightly more contemporary REMS (Resonant structure and Electronic circuit Modelling System) effects.

Taking Control

The D4 has hardly any hidden menus and almost all its controls are on the top surface, so what you see in the pictures is pretty much what you get. The no-nonsense Mode knob makes it possible to select the majority of functions pretty quickly, but when editing a track or effect, or changing the rhythm settings, it is necessary to delve into a sub-layer or two using the Value knob, the two Cursor keys and the Select and Exit buttons.

The most frequently used controls are the five pan knobs in the centre of the recorder. I call them pan knobs, but they actually perform a number of functions depending on context. Sometimes they adjust effects parameters, while at other times they control the send level of an effect. They even double up as buttons when pressed, and are used for selecting on-screen options or track record assignment. Various screen icons flash on and off telling the user what the knobs are ready to do at that moment, so it's necessary to read the manual carefully to find out what everything means.

The D4 is capable of recording two tracks simultaneously via the two rear-panel quarter-inch jack sockets. Routed to the second input channel is an XLR socket, actually situated on the top of the D4. The input allows a balanced mic lead to be connected, but no phantom power is available. There is also a built-in mic that can be used either for recording or so that the on-board chromatic tuner can monitor acoustic instruments. Also round the back are two RCA phono sockets proving the stereo output, and a USB port which allows song files and MP2 mixes to be backed up to a Mac or PC. One further rear-panel jack socket enables a footswitch to be connected and used to trigger drop-ins. The only other I/O left unmentioned is the headphone socket, placed on the right-hand edge together with its Walkman-style volume wheel, and the Card slot which is found underneath the transport buttons.

Korg D4 I/O.Korg D4 I/O.Photo: Mike Cameron

Recording & Effects

In keeping with the entry-level multitracker ethos, recording audio is a simple process. Once an instrument or mic is connected to an input, its level can be set using one of the two corresponding Input Level knobs, each with its own clip-warning LED. From there, the user has simply to engage one of the two Track Assign buttons and then press the appropriate Rec Select knob to route to a track. Helpfully, as soon as a recording is stopped, the D4 automatically saves to the card. During recording, a selection of insert effects and processors are available, courtesy of the Guitar/Mic and Insert/Gtr+Vo buttons. Setting up the appropriate effects is not quite so elementary, though, due to the way the D4's 93 effect algorithms have been organised.

The first thing to understand is that effects cannot be picked individually; they have to be chosen as part of a pre-arranged Chain. There are 11 Chains in all, which are inexplicably named from 'A' to 'E', and then from one to six. By consulting the table at the back of the manual it is possible to identify the Chain best suited to a particular purpose, and then select a Program preset which is created using that Chain type. Again, it's necessary to consult the manual to find out which Chain each of the 99 Programs belongs to. Individual Chain effects can be turned on/off and swapped like for like, so, for example, one cabinet simulation can be exchanged for another. It's not possible to rearrange effects into any order, though; if the sequence is not suitable then a more appropriate Chain has to be picked as a starting point. Certain key effect parameters are editable using the aforementioned pan knobs, and newly adjusted programs can be saved into one of 99 user slots.This block diagram, which appears within the D4's manual, shows how the audio and effects routing is configured.This block diagram, which appears within the D4's manual, shows how the audio and effects routing is configured.

The effects on offer clearly show that the D4 is primarily aimed at the guitarist. The first three Chains are designed for guitar, all providing 28 amp models designed to emulate the best-known products of the last few decades. Amps can be mixed and matched with cabinet models too, so that, for example, you can have the emulation of a Vox AC30 amp driving a cabinet belonging to a completely different model.

Given that there is so much for guitarists, the D4 is strangely lacking in Chains arranged to allow two independent sound sources to be recorded with different types of processing. For example, only Chain 5 and Chain 6 offer two independent parallel processors, and both Chains have fairly limited menu options. Chain 6, for example, inserts a cabinet simulation on track 1 or track 3 and a limiter on track 2 or track 4, but it only gives 10 cabinet choices and just the one limiter! Some of the other Chains do provide stereo in/out options for applying suitable effects to things like keyboards or drum machines, but, by and large, mono recording is favoured.

The actual mixer part of the D4 is basic. It is possible to pan each track, set its level, and bounce selected tracks together, but there's no channel EQ, and no direct way to route tracks to an external effects processor. The internal effects do offer a range of four-band EQ options, as well as a number of dynamics processors, but they have to be used as part of a viable effects Chain.

The Record Mode position of the Mode dial provides a couple of ways to submix tracks and their effects so that more overdubs are possible. When Bounce is selected, tracks are mixed to a spare track (or tracks), together with effect treatments and any additional input signal. Alternatively they can be 'Mastered' to a track pair via a stereo compressor, limiter or reverb. The MP2 mode actually creates and stores a new song file on the card, so mixes can be bounced down at any time without affecting the original track data.

The D4's editing options include Copy, Insert, Erase, Delete, and Time-expansion/compression. Edits can be made by simply positioning the two locate points in the desired start and end locations. Although the locate points can also be used to jump to points within a song, there are no song markers. I should also briefly mention the rhythm generator which is basically a glorified metronome offering 87 patterns. The tempo, time signature, and level can be changed, but it's not possible to build a drum arrangement from different patterns.

In Use

Although the D4 is designed to be fairly straightforward to use, it's not as user-friendly as it could be. It certainly does take time to get to grips with the multi-function pan knobs and the effects Chain arrangements. Usability would be improved if it were possible to set song markers — even just a few would help the user to get around. Navigating is best achieved by turning the Mode dial to Locate and then adjusting the time value directly to move through the track.

The effects are of a fairly high standard relative to the low-cost nature of the D4 itself, and I can't imagine any guitarist feeling that there aren't sufficient amplifier, cabinet, and guitar-pedal emulations. I particularly enjoyed playing with the included guitar-synth effect, which offers a range of sine and sawtooth waveforms, octave shifts, and portamento options. Some rather creative results are to be had once a suitable threshold setting is found, and I'm sure a few guitarists will find creative uses for it. It's also worth mentioning that all the standard delays and reverbs were effective and nicely programmed.

The D4 records directly to an internal Compact Flash card, and capacities of up to 2GB can be used.The D4 records directly to an internal Compact Flash card, and capacities of up to 2GB can be used.Photo: Mike Cameron

As regards sound quality, I have no gripes. The D4 records cleanly, having no hard drive to generate machine noise. The very short faders and stumpy on-screen metering create the feeling that the D4 has a limited dynamic range. Nevertheless, the sound quality is good enough for demo work, and even the Economy mode sounds OK.

Some multitrackers I've tested recently have been rather sluggish in USB mode, but the D4 works smoothly and quickly. Backing up the demo track, 'Boa Blues', to my PC took just 40 seconds, for example. If a stereo MP2 song file has been created from a mix and stored on the card, it too is easily copied across from folder to folder, just like any audio file.


The sorts of moans one would normally have were this a larger multitracker, such as the lack of mute or solo buttons, are not really relevant here. However, phantom power would have been nice, some more song navigation tools are needed, and there should be some degree of channel EQ available, particularly as the effect Chain structure limits how and when EQ can be used.

There's no denying that Korg have been clever in the way they've made the pan knobs perform a number of jobs, but I'm sure some users will find the design confusing. Korg could have included a few more controls by making the D4 larger, and it would still have been portable: the widespread adoption of laptop computers has shown that people are willing to carry something larger than the D4 as hand luggage. A laptop-sized D4 could also have a larger screen, more dedicated buttons, and possibly an internal power supply, giving it enough weight to prevent a tugged guitar lead pulling it off the table top!

Now that 2GB Compact Flash cards are available, Korg may want to think about introducing an uncompressed recording facility which operates at 44.1kHz sampling rate, particularly as the D4 already has 20-bit A-D and D-A converters. I'm not sure why the option is not available already, unless the Compact Flash medium can't exchange data fast enough.

At this UK price, the D4 is one of the most affordable products of its type on the market, but its feature set is limited. All in all it offers a cheap way to record simple demos, and seems like the modern-day equivalent of the cassette four-tracks many of us grew up with.

Published September 2005