Rane MPE series, User Manual

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26 Rane MPE Users Guide
Appendix A: Error Codes
The MPE scolds you with error codes (on the
SYSTEM display) whenever you enter a key press
that is invalid. These error codes are defined below.
Er.1 Er.1
– Entry to mode or function not allowed.
This message appears when you try to enter a
mode or function from the wrong mode. For
example, if you try to access the EQ Edit mode
clear function from the Normal Operating mode,
you are scolded with this message.
Er.2 Er.2
– Number out of range.
You are trying to enter a number that is too large
or small for a particular parameter.
Er.3 Er.3
– Key undefined in this mode or function.
You are pressing a key that is invalid (i.e. un-
used) for a particular mode or function.
Er.9 Er.9
– Invalid lockout security code.
You typed in the wrong security code.
L.O.1 L.O.1 – Device is locked out at level 1.
You may recall a Stored Memory, but you cannot
change it.
L.O.2 L.O.2
– Device is locked out at level 2.
All keypad entries are disallowed, except the
proper unlock procedure.
Appendix B: Ramp Details
(For advanced users only, not necessary for
normal operation)
Any instantaneous change to the level of a band-
limited audio signal is accompanied by a small
overshoot. Aurally, this reveals itself as a “pop”.
This is a fact of life, as dependable as taxes and
death.
When an equalizer creates a rapid level change a
small pop is emitted. The bigger or more rapid the
change, the bigger the bang. This is not a problem
with manually adjusted analog equalizers since it is
unlikely that anybody could move a slider fast
enough to cause an instantaneous change of level.
However, a programmable equalizer changes curves
in a matter of microseconds—plenty quick enough
to generate an onslaught of thundering snaps, crack-
les and pops.
The MPE’s provide a special control to combat
this nemesis, the EQ Ramp. The EQ Ramp con-
strains curves to change in small increments, pro-
grammable in decibel step sizes. This causes the
instantaneous curve changes to be small, reducing
the magnitude of any overshoots to inaudibility.
Although the EQ Ramp is adjusted in terms of
decibel step size, you may wish to determine how
much time a curve transition requires. This is not
entirely straightforward. The ramp operates in the
“decibel step size domain”, rather than the “time
domain”. This appendix delineates the process of
translating from the decibel domain to the time
domain.
The software internal to the MPE is “multitask-
ing”. Concurrent tasks include; scanning the keypad
and processing user input, refreshing the LED
displays, watching for MIDI, and changing EQ
curves. The MPE’s CPU is time shared among these
tasks. Changes to EQ curves are scheduled in this
multitasking environment. Consequently, while a
curve changes it must share the MPE’s CPU with
other active tasks. The result is a variation in the
time a curve transition requires. What all this means
is the calculations that ensue have a small error
tolerance of several milliseconds.