twisted electrons MegaFM Manuel utilisateur
USER MANUAL
June 2nd 2020
We always value feedback and ideas, so feel free to reach out.
Please check the website for the latest firmware!
THANK-YOU!
Thank-you for adopting MEGAfm, the product of several years of work &
play. We are particularly fond of the YM2612 as they offer a unique gritty
texture that is uncommon in the FM word, plus hands-on FM experience
that is unprecedented in the hardware FM synthesiser world.
We hope that you will enjoy making music with MEGAfm as much as we
have enjoyed and continue to enjoy developing it!
YM2612 Overview
“The Yamaha 2612 Frequency Modulation (FM) sound synthesis IC
resembles the Yamaha 2151 (used in Sega’s coin-op machines) and the
chips used in Yamaha’s synthesisers.
It is famously known as the Sega Megadrive’s voice.
An FM channel is capable of expressing, with a high degree of realism, a
single note in almost any instrument’s voice. Chords are generally created
by using multiple FM channels.
The standard FM channels each have a single overall frequency and data
for how to turn this frequency into the complex final wave form (the
voice). This conversion process uses four dedicated channel components
called ‘operators’, each possessing a frequency (a variant of the overall
frequency), an envelope, and the capability to modulate its input using
the frequency and envelope. The operator frequencies are offsets of
integral multiples of the overall frequency.
There are 6 FM channels. Channels 3 and 6, have the capability to use a
totally separate frequency for each operator rather than offsets of integral
multiples (ch3 special mode). This works well for sound effects and
experimental instruments.!“
Operators
There are four dedicated operators per voice which may be arranged in
eight different configurations, called “algorithms”. Following is a diagram
of the algorithms.
Slots are indicated by shading.
!!!
Envelope Specification
The sound starts when the key is depressed, a process called ‘key on’.
The sound has an attack, a strong primary decay, followed by a slow
secondary decay. The sound continues this secondary decay until the key
is released, a process called ‘key off’. The sound then begins a rapid final
decay, representing for example a piano note after the key has been
released and the damper has come down on the strings.
The envelope is represented by the above amplitudes and angles, used
in the above diagram are:
!
Thanks MAXIM for the above excerpts: !
https://www.smspower.org/maxim/Documents/YM2612
TL
Total level, the highest amplitude of the waveform.
AR
Attack rate, the angle of initial amplitude increase. This can be made
very steep if desired. The problem with slow attack rates is that if the
notes are short, the release (called ‘key off’) occurs before the note has
reached a reasonable level.
DR
The angle of initial amplitude decrease.
SL
The amplitude at which the slower amplitude decrease starts.
SR
The angle of secondary amplitude decrease. This will continue
indefinitely unless ‘key off’ occurs.
RR
The final angle of amplitude decrease, after ‘key off’.
Voicing
MEGAfm offers up to 12 voice polyphony.!
The 12 voices are spread across two YM2612 chips.
In all modes you can use the fat knob to detune the voices.
Hold voicing mode button and the fat knob becomes glide.
Glide knob determines the time it takes for each voice to change pitch
when a new note is played.
Mono Mode:
When a single TS 6.35mm jack is plugged into output1, both chips are
summed to output1.
Stereo Mode:
When a second TS 6.35mm jack is plugged into output2, the 2 chips will
be split between outputs 1 and 2 (6 voices per chip/output)
There are 4 Voicing modes available. Press the voicing button to change
the current voice Voicing mode.
Poly12
12 voice polyphony scattered between both chips in a!Left/right/left/
right etc manner
Wide6
Both chips play the same 6 notes but can be detuned with the fat knob
Dual ch3
YM2612 offers a special mode where the 4 operators of channel3 can be
individually detuned to arbitrary frequencies as described above in the
YM2612 Overview. Recommended for experimental / percussive sounds.
Unison
All voices are played at once in unison and detuned using the fat knob.
Turn the fat knob clockwise to gradually detune all 12 voices. At
maximum fat, the 12 voices are arranged in a chord.
Fat
Use the fat knob to detune the 12 voices in any voice mode. In Unison
mode you can detune the voices from slightly detuned (aka fat) all the
way to a grand chord, THX style!
In all other modes, you can detune the voices either by 1 semitone or 1
octave. See setup to choose between the 2 options.
Glide
When you hold the voicing button the fat knob becomes glide. Adding
glide increases the time it takes each voice to reach its new pitch.
Volume
Use the volume knob to set the volume of the current preset.
Note about volume: A digital potentiometer is used to set the volume so
that it can be recalled between presets. Digital potentiometers can make
a click noise known as zipper noise when changing values, in order to
reduce this noise the volume is only updated after the knob has been
adjusted, not during so please allow a quarter second for the volume to
change.
Preset tuning!
Hold voicing and use the VOL knob to tune your preset within a 1 octave
range.
Algorithms & Feedback
Use the algorithm knob to select any of the 8 algorithms and the
feedback knob to set the amount of operator1 feedback.
Note: both parameters can be modulated by LFO!
Vibrato
Use the depth knob to add vibrato to the overall pitch of MEGAfm.
Use the vibrato rate knob to set the vibrato’s speed.
The vibrato can be configured to sync to incoming MIDI clock at 8
different speeds, please refer to SETUP instructions for more details.
Arpeggiator and Sequencer
When unison voice mode is active the arpeggiator can be used.
The arpeggiator has 7 modes:
Up (shown as “UP” on the numeric display)
Down (shown as “dn” on the numeric display)
Up/Down aka pendulum (shown as “Ud” on the numeric display)
Random1 (shown as “r1” on the numeric display)
The arpeggiator chooses and plays any of the held keys at random.
!Random2 (shown as “r2” on the numeric display)
The arpeggiator chooses and plays any notes at random.
Sequencer1 and 2 (shown as “S1” and “S2” on the numeric display)
The arpeggiator acts as a sequencer playing up to 16 notes that can be
recorded via!MIDI.
In S2 mode, the sequencer avances a step every time a key is pressed
and not in S1 Similarly to a Casio VL Tone.
Reminder: The Arp is only active when in unison mode
Recording a sequence
To record a sequence press rec to activate recording mode. The rec LED
will flash.
Now play up to 16 notes via MIDI. Each preset can store up to 16 notes.
Every time you input a note, the step recorder will advance and the
numeric display will show the current step.
You can use the preset up button to skip a step. No note will be played.
You can also go back a step with the preset down button if you wish to
correct a note.
The arpeggiator can be set to sync to incoming MIDI clock at 8 different
speeds defined by the rate knob. Please refer to Setup for details.
Modulators ( Lfo 1 to 3)
Any knob or fader can be modulated by up to 3 lfo modulators at once.
To link a knob or fader to an lfo
move a knob or fader and press a chain link button. Click the
chain button a second time to unlink a knob or fader from an lfo.
The LED above the chain button indicates whether the
modulator is linked or not. Each knob or fader can link to up to
3 LFOs at once.
To unlink all the knobs/faders from an lfo!
hold the chain button for 4 seconds, until the letters CL appear on the
numeric display.
Table des matières
Autres manuels twisted electrons Synthétiseur
