DPX 1

Sample Player

The First Sample Player In December 1986 Oberheim launched the world's first digital sample player - the DPX-1. This 2U rack module could replay the sampled sounds from disks originally recorded on the Emulator II, Sequential Prophet 2000/2002, Ensoniq Mirage, and the Akai S900

Specifications The DPX-1 is eight voice polyphonic, with MIDI and optional SCSI. With a 1 MB memory, all data is converted into a 12 bit linear format for replaying. These provides 512k samples. One Bank of EII samples can be loaded at a time, all 100 presets can be accessed via a 2 character red LED display. Both 3.5" and 5.25" floppy diskette drives are in built.

MIDI SDS The DPX-1 is the only other device that can read the unique special Emulator II format diskettes, and its also supports MIDI Sample Dump Standard (SDS). Which means you can get your EII sounds into other samplers !

You can format a 3.5" diskette, and save your EII 12-bit sounds onto a new reliable diskette. If you are an EII user who wants to continue using your ace samples into the 21st century, this is THE puppy to get ! They are even dead cheap to buy.

Sample Replay The Oberheim DPX1 reproduces sampled audio data read from 3.5" or 5.25" floppy diskettes or received from MIDI via Sample Dump Standard. All sample data is converted to 12-bit linear data format. The DPX-1 will accept disk data from:

• Emulator II
• Prophet 2000/2002/2002+
• Mirage rack and keyboard
• Akai S900

Front Panel The DPX1 has both 3.5" DS/HD and 5.25" DS/DD floppy drives, which should have their cardboard templates inserted when the DPX1 is being transported. There are a small number of front panels keys:

• LOAD DISK
• DECREMENT
• ENTER
• INCREMENT
• FUNCTION SELECT KEY

There are 2 LED's to show when the disk is busy and when the disk encounters an error. There are 6 function indicator LED's to show which function is selected. There is a 2 character red LED for displaying information, and a volume slider. The power switch is on the back, how inconvenient can you get!

MIDI The DPX-1 has the usual MIDI IN, OUT and THRU.Basic channel select for transmit and receive, modes 1, 3 and 4 (Prophet 2000 only) is supported. Controllers on/off, patch change commands on/off, controllers supported as defined by the sample disk being replayed. MIDI sample dump standard is supported.

Audio The DPX-1 has a single unbalanced audio output. Although the optional CDROM interface adds another 8 mono outs. All on 1/4" jacks

Analog Synthesizer Inside The DPX-1 runs with a VCF/VCA/LFO analog architecture. The parameters for these are read directly from the sample disk. Only the filter cutoff can be modified manually, initailly just wide open or as per the sample disk. But in release 2.0 you can vary the cut off from 0 - 99 from the front panel.

Missed Again The DPX-1 is the only other device that can read the unique EII diskette format. However the DPX-1 was not a great success, as is the case with every other replay sampler that has been manufactured. Users prefer to be able to sample as well, and replay samplers are not much cheaper or simpler to build than fully fledged samplers. By the time the DPX-1 was out, sampling had moved on from the 1984 EII. Akai were making their mark with the new 12-bit S900, and then 16-bit S1000 rack mount samplers. E-mu Systems had released the awesome 16-bit EIII, and put an EII on a chip with the Emax. The DPX-1 was a great idea that sold to pro musicians who wanted to tour their EII's.

A Rack Mount EII The DPX-1 offers the Emulator II user a smaller and more reliable rack mount version - highly attractive! It uses the same analog SSM filters, so it sounds brilliant. It can even be found with an external SCSI connector. The DPX-1 converts the Emulator II 8-bit samples into 12-bit, after it has loaded the diskette and before you can play the samples. This takes a few seconds (lots of time for a bird run !). You can now play the samples as you would on your EII, but there's more!

Technical Description

Architecture The Oberheim DPX-1 is an 8 voice polyphonic digital sample player, which uses a Motorola 68000 microprocessor to reproduce 8 and 12 bit digital samples. The DPX-1 is entirely controlled by computer software which is loaded from internal EPROM at boot time. The DPX-1 uses quite a collection of TTL logic in addition to the usual analog output channels. There are two rather neat and well laid out circuit boards, sitting on top of each other. The lower board has eight voice channels, and the upper board has the memory chips and microprocessor.

Sample Memory There is 1MB of internal sample memory on the upper circuit board (although we can only find 24 x 32k bytes = 768k bytes on ours, which equates to 512k 12-bit words). The memory can not be expanded.

Disk Drives There are two internal TEAC disk drives fitted to the DPX-1 on the left hand side, one DS/DD 3.5" and the other DS/DD 5.25". They are controlled by a standard WD1770 controller chip, and they are daisy chained together. Being TEAC drives means there are still available in the reconditioned market, the model numbers are FD135 FN50-U (3.5")and FD55 FR550-U (5.25").

OS Releases The DPX-1 loads its operating software straight from EPROM, ignoring the native OS on the diskette it is reading. The latest version we know of is 2.2.

Digital Sample Replay The DPX1 plays samples in 12-bit linear format, converting 8-bit samples to 12-bit where necessary. The DPX-1 can replay samples from the following samplers:

• Emulator II
• Prophet 2000/2002/2002
• Mirage DSK9/DMS8
• Akai S900

Analog Filters The DPX1 has analog filters ! The usual SSM2045 is once again pressed into use for each of the eight voices. They sound very pleasant - although the bass drops off when they are driven into high resonance values.

That Sound The EII has a distinctive quality sound, which belies the use of 8 bit sampling. The DPX-1 makes a very good emulation of an Emulator II ! The warm analog filters and the grit of the low sample resolution still stand out, although the loop points seem a bit more obvious.

Long Term Survival The DPX-1 is well engineered at a physical and circuit board level, with high quality components. It gets around two of the weak points in the EII (the fading LCD, and the difficult to replace diskette drives). It does still uses unique chips which are hard to source (like the SSM filters and latches, and the PAL chips), but these are less likely to fail than the hardware and PSU. The ability to copy EII sounds to 3.5" diskette, makes this a long term platform for playing EII samples.

Operating Instructions

Overview The Oberheim DPX-1 has a very simple operating system which is controlled by the 5 front panel buttons.

Disk Loading Place the diskette you wish to load into either the 3.5" or 5.25" drive. The DPX1 will always load from the 3,5" drive first (if there is a diskette in it!). Now press the LOAD DISK button once. The DPX1 will now load the samples, and the BUSY LED will light up. The 2 character LED display will quickly show the host sampler and display:

• E2 = Emulator II
• A9 = Akai 900
• P2 = Prophet 2000, 2002/2002+
• En = Ensoniq Mirage
• Cd = CDROM
• UF = Sample Dump

Once the sample has loaded it will be ready to play, unless it is 8-bit sample - in which case the DPX1 will process it into a 12-bit sample. This conversion takes the Motorola 68000 microprocessor about 30 seconds (the BUSY LED will remain lit until the processing is complete). The DPX1 will then provide Bank 0 as the active sound set.

Function Select Six options can be sequentially selected by using the function select button.

Patch Select Select this option with the function select button, and then select the bank you wish to use (00 - 99) with the INCREMENT/ DECREMENT buttons, followed by ENTER. There will be a decimal place next to the bank number if it is not the current bank.

MIDI Channel Select this option with the function select button. The current MIDI channel will be displayed (1-16, On for omni). You can change the setting by using the INCREMENT/DECREMENT buttons, followed by ENTER. You will need to save this setting to disk, as MIDI channel is disk specific and it is not stored as a generic parameter within the DPX1. The BUSY LED will light when the DPX1 receives MIDI information (e.g. notes).

Display The 2 character LED displays the following messages:

• Ld = Loading Diskette
• nd = No Disk
• on = Selected Paramter is Enbaled or Omni
• off = Selected parameter is disabled
• bd = Blank Disk
• nb = Not Blank Disk
• nF = No Format
• Pd = Protected Disk
• bS = Bad Sample
• dE = Disk Error
• SE = MIDI Sample Error
• iE = Internal Error
• 2.2 = operating system version number MIDI information (e.g. notes).

Fine Tune Select this option with the function select button. The DPX-1 can have its tuning adjusted. There are six options which are selected by the INCREMENT/DECREMENT keys followed by the ENTER key:

• pi = Oscillator Pitch
• Fi = Filter cut-off adjustment
• tn = Transpose Note 2.2 feature only
• tr = Transpose Range 2.2 feature only
• tS = Transpose Sample 2.2 feature only

Each tuning control can be adjusted from 00-99 (50 is the mid point and default) using the INCREMENT/DECREMENT keys, remembering to press ENTER to save the adjustment to disk.

Data Dump Select this option with the function select button. The DPX1 can dump its sample memory to a 3.5" diskette or over MIDI. There are three options which are selected by the INCREMENT/DECREMENT keys, followed by the ENTER key:

• dd = Data Dump - save memory to diskette
• SP = Save Parameters - Press ENTER to write current configuration parameters to a backup disk containing sample data
• Sd = MIDI sample dump receive/transmit
• AL = All ememory ready for MIDI sample dumping

MIDI Controller Select this option with the function select button. There are two options which are selected by the INCREMENT/DECREMENT keys, followed by the ENTER key:

• CE = midi controller enable - the DPX1 will respond to midi controllers such as pitch bend, vibrato, volume, sustain and pressure
• EC = midi echo - combines information generated by the DPX1 (i.e. patch change) and the data received from midi in and sends it via the OUT port

Extended Function Select this option with the function select button. There are three options which can be selected by the INCREMENT/DECREMENT keys, followed by the ENTER key:

• Fd = formats and verifies a DS/DD 3.5" diskette
• Filter Limit = enables/disables filter tracking
• Ld = load diskette
• do = dual oscillator mode (for the Mirage only)
• 2.2 = operating system version number

OS Version 2.1 and 2.2 will format DS/HDDiskettes, very useful.

Upgrades & Add Ons

Factory Upgrades The Oberheim factory has long since disappeared, and there are no upgrades or spares for the DPX-1 except second hand. There were two factory upgrades, with two vacant slots in the back of the standard DPX-1.

8 Outs and RS422 The DPX-1 could be upgraded with eight individual voice outputs on jacks, and a 9 pin RS422 connector. The RS422 enables the OMI CDROM drive (CDS3) to be connected so that EII CDROM's from OMI can be read. The OMI drives were Sony CD mechanisms with an RS422 interface. They were the first CDROM drives for use with a sampler. The OMI sample disks are very high quality. See the EII section for more info.

SCSI A SCSI interface card could be fitted which enabled the DPX1 to link up to the Oberheim HDX-20 Hard Disk Unit (2U Rack). The individual output upgrade is a pre-requisite to the SCSI upgrade. The DPX-1 does not work with ZIP drives.

Memory The sample memory can not be upgraded.

HDX-20 Music Storage System Oberheim produced an add on hard disk unit, the HDX-20, in a separate 2U rack unit. The unit came with a SCSI interface board for fitting into the DPX-1, a 25-pin SCSI cable, upgrade instructions, a 128 Kbytes memory upgrade for the DPX-1, OS Version 2.2 on two EPROM's, and the actual HDX-20 (which formats to 20 MB). The drive holds a total of 19 sample banks. The Output Expansion upgrade MUST be fitted in the DPX-1, for the SCSI upgrade to be able to be installed. It contains the necessary SCSI external connector and an interface chip.

Technical The HDX-20 contains a 5.25" Seagate ST238R 38 MB hard drive, which spins at 3600 rpm, and has an average seek time of 65ms. The drive has an ST412 interface not SCSI. A separate SCSI interface board sits alongside the drive in the 2U case. The drive formats at 20 MB. This appears to be the maximum space a DPX-1 can format and access.

Multiple Drives The SCSI DPX-1 can support up to 7 external SCSI devices, although the manual recommends only two devices are connected due to the need to keep SCSI cable lengths to a minimum. An HDX-20 can be shared by two DPX-1's, and a DPX-1 can access mutiple HDX-20's. There are two 25-pin SCSI connectors on the back of the case.

Preloaded The HDX-20 came preloaded with 19 banks of samples.