Other Features
There is a note stack within the firmware to allow the midiDAC to remember notes pressed.
Thus if two or more notes are pressed at the same time, the oldest notes will be remembered
so that if the more recent notes are removed the pitch will return to the still pressed older
notes.
The midiDAC also includes a TB303 style slide circuit. This can be turned either by engaging
a switch, or by playing two notes at once. The pitch will glide up or down to the most recently
pressed note. A pot can control the speed of the slide.
Note retriggering is an option that can be changed on the fly. A simple switch or link can be
used to select whether it is on or off. Ordinarily, when a note is pressed the gate always goes
high. However, if a second note is pressed while another is still held down, the pitch CV will
change but the gate remains high. The envelope generators on your synth will not retrigger.
This is typical of Moog synthesisers. It can be useful. The 'Retriggering' mode allows the gate
to drop momentarily when any new note note is pressed if there is a note already down. Thus,
when the pitch CV changes, the envelopes will be retriggered, just like a normal note. This
allows fast keyboard runs to be easily achieved.
The new suggested panel layout incorporates both the glide and re-trigger switches.
The midiDAC features a built in midi THRU port. This essentially produces a copy of the midi
input signal which can be then fed to another midi unit. Both the opto isolator and the THRU
buffer are high speed devices so there is minimal skew. Skew, in this case, is the difference in
rise and fall times of the digital midi data stream. Each opto-coupler the midi data has to travel
through will alter the shape of the data waveform. This is sometimes thought of as a delay but
this is not strictly true. What happens is that for each opto-coupler and cable run the midi
signal has to pass through the more skewed the signal will be. Excessive skew will cause data
corruption, eg. notes will be randomly dropped or held, particularly if there is a lot of
information being sent down that midi cable. Opto-couplers also deteriorate with use so have
a limited lifetime. It is therefore not recommended to have long midi chains. Normally just two
or three devices in a row is sufficient.
The module requires a split supply of +/-15V at 40mA and -30mA. +/-12V operation
is not supported.
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