Basic info
The Electrongate DMX1554E is a new voice card for the Oberheim DMX
drum machine. It uses the same circuits and technology as the original Oberheim
single EPROM voice boards, using the same sample length, DAC, filter and basic logic
design, so it will sound the same. It is a direct plug-in replacement for any of
the seven DMX voice cards with two Molex connectors.
Six standard voice board configurations are available, matching the
original Oberheim board setups for Bass, Snare, Hi-hat, Tom 1/2, Perc 1
(tambourine/rimshot) and Perc 2 (Shaker/handclap).
Manufactured using all through-hole components, like
the original, this voice card is easy for the experimenter to modify using
simple soldering tools. No surface mount parts are used. The configuration
jumpers and components are located in the same positions as the original.
New features
The DMX1554E has a wider tuning range than the original, using a 25K tuning
pot instead of the original 10K pot.
An optional built-in Zero Insertion Force (ZIF) socket can be ordered.
Note: There is not enough room between voice boards in the DMX to add ZIF sockets
by stacking them on a regular socket. They must be soldered directly to the board.
The original 24-pin EPROM socket has been replaced with a 28-pin socket. A
jumper setting allows choosing the original 2732 EPROM size, or larger capacity
2764 or 27128 EPROMs.
Where the 2732 holds one audio sample (or a pair in the case of the PERC voices), a
2764 supports two independent samples or pairs of samples. Selecting one
or the other is done with an optional switch, either connected directly to the
voice board, through the DMX external control voltage input, or through the motherboard
connector, using previously unused pins.
Using the external CV input is the simplest way of switching between two samples without
having to drill holes in the DMX case or deal with internal wiring.
Note: Using the CV input for
switching means that external tuning or volume controls are disabled for the voice board in
question.
Multiple DMX1554E voice boards can be switched in parallel with a single switch, or
individually.
A 27128 will support four samples, selected with two switches, with four possible combinations.
All configurations may be ordered with the original sample EPROM, an
alternate sample of comparable length, or a double sample of your choice.
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