|
Oberheim DPX-1 : 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:
- the 3.5" is FD135 FN50-U
- the 5.25" is FD55 FR550-U
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.
|
Site Options