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Oberheim DPX1 Sample Player

Instead of following other keyboard manufacturers sheep-like into sampling machines, Oberheim have come up with a unique device which doesn't sample but replays disks from several other samplers. Paul Wiffen investigates.

Instead of following all the other electronic keyboard manufacturers sheep-like into sampling machines, Oberheim have taken a slightly different approach to the market and come up with a machine which doesn't sample but replays disks from several other machines. Paul Wiffen, longtime supporter of the Prophet samplers, finds it just what he's been looking for.

Like most of the clever ideas in the field of electronic musical instruments, the design philosophy of the Oberheim DPX1 seems an obvious enough move with the benefit of hindsight. Most musicians who use samplers don't have the time, the facilities or the inclination to record their own samples and then combine them into presets with smooth transitions between samples and all the filter and amplifier settings to make for expressive performance. And who can blame them? If the majority of people weren't going to do it with the Prophet 5, where everything you needed to make a sound was laid out on knobs for easy access, then they aren't going to want to go out hunting for sounds with a microphone and then spend hours (and it often does take hours!) combining them into usable multisamples. What programmers like myself tend to forget is that we're paid to come up with good sounds - most musicians don't start being paid until they start playing.

In addition to this, no one sampler on the market has all the good disks. The Emulator II, which is generally reckoned to have one of the most complete sound libraries around, lacks a usable electric guitar, while the Mirage, decried by many professionals for its low bandwidth and short sample times, has the best electric guitar disk at any price. And whilst there are some excellent disks for the Prophet 2000 series, Sequential's disk policy (or lack of one) has meant that these can be difficult to track down. And anyone who's ever tried to sample across from one machine to another will know how difficult and time consuming that can be (and how the result is rarely as good as the original!). So, to get the best sounds from sampling, you need to have access to several different samplers.

Or you did until the DPX1 came along! Now there is one neat 2u high rack box which will play all the disks from the Emulator II, Prophet 2000 and Mirage (with those from other machines to follow soon). So you can pick and choose the best disks from each sample library and have them play back from one unit.


Of course, this is only of value if the machine does a good job of imitating the original hardware on which the disk was made. The whole procedure is much more complicated than you might think. On each disk, the data is saved in two parts: the actual sample waveforms and the preset information (including the settings of the analogue filters).

The first problem that Oberheim's engineers had to overcome was that the data format for each of the sampler disk types that the DPX1 covers is different. The Ensoniq Mirage uses an 8-bit linear format, the Emulator II uses 8-bit companded, and the Prophet range use 12-bit linear. So, to begin with, the DPX1 has to be able to understand three different sample resolutions, which is like you or I speaking three different languages, one after the other without a break.

When you load a disk into the DPX1 (whether an Ensoniq or Prophet disk into the 3½" drive or an EII disk from the 5¼" drive), then the DPX1 takes a second or so to identify which type of disk it is. It then shows either En, P2, or E2 in the display and proceeds to load the sample data.

Once the sample data is loaded (which takes roughly the same amount of time as on the original machines), then the DPX1 has the harder part of its job to do. Samples on their own are not that useful, so the DPX1 has to read and interpret all the mapping and analogue parameters off the disk. This involves not only the placing of the samples on the keyboard, but also the setting up of the analogue controls particularly the filter, separately for each sample. This is the most difficult thing to do as the quality of the sound depends very much on the filter hardware, which is different in each of the samplers. Indeed, sometimes you can hear the difference in filter settings between different instruments of the same model.


So how does the DPX1 cope with data conversion and analogue settings then? In other words, does it sound as good as on the original instrument that made the disks?

The initial session I had with the DPX1 produced very good results in most cases. The various different Mirage, Prophet and Emulator disks I took along to the Oberheim factory all loaded without problems and gave very impressive reproductions of the original sounds. On first listening, I couldn't hear any difference between disks loaded on the Prophet or Emulator and DPX1, and some of the disks from the Mirage actually sounded better than on the original machine. The DPX1 actually eliminates some of the distortion in the Mirage replay process, so that the disks play back more cleanly than on the Ensoniq. Of course, the DPX1 cannot overcome any of the limitations imposed by the original sampling (so you will expect to find the best bandwidth and fidelity on the disks made on the Prophet) but, nevertheless, anything which was acceptable on the original sampler will be acceptable on the DPX1.

At a later stage, when I got the chance to A/B disks on the DPX1 and on the samplers on which the disks were made, I did start to notice a few little anomalies, particularly on the Prophet disks. This was mainly on samples I had made which used rather severe filter tracking to cut out aliasing at the bottom end of its range while keeping the sample good and bright at the top. Such samples remained rather dull on the DPX1. On another disk there was not quite the octave available to transpose the sample above its original pitch because it had been sampled flat originally and had had to be tuned up. These were all cases of extreme settings which are not usually used. However, when I showed these to the engineers at Oberheim, they soon had these problems cleared up, so unless you come across a unit with a really early software revision, you won't encounter these problems at all.

The only problem which occurs with Mirage disks is that the Mirage provides for two oscillators per voice, whereas the DPX1 only has one. Of course, on many Mirage disks the second oscillator is not used, but for those where the sound relies on two oscillators per voice, the DPX1 has a dual oscillator mode. When this is switched on the disk replays exactly as on the Mirage, albeit with only 4-voice polyphony.

Because there is less distortion on the Mirage samples when played back on the DPX1, the closed filter settings which are set on many of the Mirage disks (to remove this distortion) do not need to be so rigorously applied on the DPX1 and the filter settings can be left more open. However, if you want the 'authentic' sound of the Mirage, the DPX1 has a Filter Limit parameter which, when switched on, prevents the filter from opening more than the original Mirage setting.

The currently installed version of software in the DPX1 loads all the disks I have for the Prophet 2000 (around 100), Emulator II (50) and Mirage (30) without any problems. My only reservation is that it doesn't implement the Stack Mode in Prophet disks, which is a useful performance option that allows you to double (or quadruple) oscillators and then detune them - and/or delay them - for chorus, echo or unison effects. Oberheim say that this is because Stack Mode does not form part of the presets on the 2000 - but while this is true of the original Prophet 2000 operating system, more recent revisions of the software allow the Stack Mode to be stored as part of a sample preset. This means that presets in Stack Mode will not sound the same on the DPX1. Perhaps in a future software revision Oberheim will include the Stack settings under the same parameter as the Dual Oscillator setting for Mirage disks, to which it is very similar.


The DPX1 is a very easy machine to use in its current incarnation. You simply place a disk in either the 3½" or 5¼" drive, press the Load Disk button (if only more machines had a single button dedicated to such an important function!). The DPX1 then checks the 3½" drive (and loads a disk if there is one present). If this drive is empty, then it will load from the 5¼" drive.

Once the disk has loaded, the first preset is ready to play. On the Mirage disks, all three set-ups of the Ensoniq machine are loaded at the same time, so you can switch between them. This is easily achieved on all disks either via MIDI Program Changes, or the Increment/Decrement buttons on the front panel, followed by the Enter button. (This is standard practice on the DPX1, using Enter to confirm a decision.) This means you can step through all the choices available without changing anything until you find the right option.

The MIDI Channel Assignment is done in the same way, selecting either Omni Mode or channels 1-16. A recent DPX1 software update also ensures that any presets on Prophet 2000 disks which were saved in MIDI Mode 4 are in Mono Mode on the DPX1 as well (you have to make sure Omni Mode is not selected for it to work properly). This is a great feature of the DPX1, as not only does it make the DPX1 as useful as the 2000 for multi-timbral sequencing, but more so, as the Oberheim engineers have implemented MIDI Pitch Bend and Modulation Wheel recognition in Mono Mode - something Sequential's engineers forgot (from now on I shall be doing all my Mode 4 work on the DPX1). This is just one example of how the DPX1 actually goes beyond the spec of the machines whose disks it reads (a bit like PC compatible computers which out-perform IBM originals).

The Data Dump section of the machine has been considerably expanded in the most recent software update. Originally, the only way samples could be transferred was via the MIDI Sample Dump standard, a useful way of getting samples into other machines, but rather slow and therefore impractical for storage and back-up. Now any disks loaded into the DPX1 can be saved to 3½" disk in an exclusive Oberheim format. This has several advantages: first, you no longer need to carry around the clumsier and more vulnerable 5¼" disks as all Emulator II samples can be re-saved onto 3½" disks; secondly, as the samples are converted and stored in the common DPX1 format, when you reload from the Oberheim format disks, all the load times are considerably reduced (for example, 10 seconds are shaved off the 40 second load time of a 512K Prophet 2000 disk); and thirdly, you can make back-ups of all your disks in case of data corruption, which can so easily happen in a studio or stage environment.

This software revision also made the MIDI Sample Dump more flexible, allowing individual sample receive and send as well as a complete memory transfer. However, while you can send the whole sample memory out via MIDI from the DPX1 front panel, you need to request individual samples via MIDI, so you will need something to provide this in order to make the best use of the facility (the only device I could track down was the Oberheim Prommer, but I expect the computer literate amongst you could write their own program to achieve this).

Apart from the Dual Oscillator and Filter parameters we looked at earlier under the Mirage disk replay, the 'Special Functions' section allows you to Format Disks and see which Software Revision is currently installed in the DPX1.


The first expansion of the DPX1 is due very shortly. This is an optional hardware upgrade which, in one fell swoop, gives you eight separate outputs for the machine, plus the ability to interface with the Optical Media CD-ROM. Much importance is attached by many people to having individual outputs, especially before they have used them! Not only do they mean that you need to have a mixing desk and loads of audio cables, but they also destroy the wonderful flexibility of voice assignment which the Dynamic Allocation on most sampling machines (DPX1 included) can give you. But, however much you may resent the limitations and extra equipment which separate outputs force upon you (and believe me, I do), there is no denying that for certain applications (drum sounds and monophonic lines like bass), they are indispensable. When first planned for the DPX1, these eight outputs would of course only have been useful on Emulator disks where the separate outputs had already been assigned (you have to assign the outputs on the source instrument because of the nature of the relationship between samples and the presets they are arranged in), but in the last few months the latest Prophet sampler - the 2002 Plus which adds eight separate outs - means that there will soon be Prophet disks about which have been saved with the 'Forced Outputs' parameter selected. The problem with separate outputs on the DPX1 is that there are very few disks around which have these ready-assigned as a matter of course. Still, if you have access to an Emulator II or Prophet 2000 then you could set up the assignment for yourself (I suppose you could even hire one for an afternoon).

DPX1 owners have another strong reason to get this hardware update fitted: the CD-ROM interface. For those of you who are not yet familiar with this product, Optical Media make a Compact Disc (CD) reader which, instead of audio data, downloads sample and preset data into a sampling machine (originally the Emulator II). Their first CD, the 'Universe Of Sounds, Vol 1', has over 500 floppy disks worth of Emulator samples on it. With the update fitted, these can now be accessed directly from the DPX1, which essentially expands the available library five-fold. And Optical Media are just about to release their 'Vol 2' CD, which will add another 500 banks. These CDs include footsteps-type sound effects so you could hire in the CD-ROM reader and the CDs for film and TV applications; studios that work in these areas all the time could even buy the player and CDs as an instant sound effects library.

Future software updates are already planned to include the ability to read Akai S900 disks, and I suspect that when the chaps at Oberheim hear the quality and range of Roland's disks, then S50 compatibility will not be far behind. I don't know whether the hardware will allow for compatibility with 16-bit machines like the Casio FZ1, but even if Oberheim restrict themselves to 12-bit machines like Emax and the Korg DSS-1, then the number of sounds available for the DPX1 will grow exponentially for some years to come.


The most obvious buyer for the DPX1 is the studio or musician who doesn't want (or doesn't have the facilities) to get directly involved with sampling but wants the sort of sounds that it provides. With the whole Emulator II library available, they have access to arguably the most complete sound library on the market without the high price tag of that machine, but with the bonus of Mirage and higher fidelity Prophet disks to supplement it. Add the hardware update and the number of sounds available for the DPX1 runs into the thousands (thanks to the CD-ROM).

But there are many other people who should think seriously about the DPX1. Emulator owners might well want a rack-mounting version of their instrument simply for its convenient size and weight (or lack of), plus the extra sounds that will then become available. For Prophet 2000/2 owners, the argument is even stronger: not only will they remedy at a stroke their patchy library situation, but because of the MIDI Overflow Mode on the 2000 they will also get a 16-voice package which can all be played/sequenced from one master unit. And with the extra capabilities of the DPX1 in Mono Mode, you can use it to sequence those sounds which do need pitch bend and vibrato, and keep the Prophet to play back those that don't! Even those who have a sampler whose disks won't load into the DPX1 at the moment, will be expanding the number of sounds they can access. Chances are that sooner or later the disks from your machine will load into the DPX1, giving you that extra flexibility.

In fact, I can't think of anyone who couldn't make use of a DPX1, whether for extra voices on the samples they already have, or access to the sound libraries of other samplers, or the flexibility of both in one machine.

Recommended price £1695 inc VAT; 8 output/CD-ROM update around £300 inc VAT.

Distributed by Sound Technology Plc, (Contact Details).

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Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Jul 1987

Gear in this article:

Sampler (Playback Only) > Oberheim > DPX1

Gear Tags:

12-Bit Sampler

Review by Paul Wiffen

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