KautenjaDSP Mini Boss User manual

KautenjaDSP

KautenjaDSP Mini Boss v2.0.0
Overview
Mini Boss is an emulation and re-envisioning of the Yamaha YM2612 audio processing unit from
the Sega Mega Drive and Sega Genesis. Mini Boss provides the key functionality of a single
operator from the Yamaha YM2612, in addition to some hacks, omissions, and re-envisioned
features, namely,
•16-bit Audio: It’s 8 bits better than the previous generation of chips! This is marketing! We’re
actually lying though – the YM2612 produced a 14-bit stream, and so does BossFight. You’re
not getting those 2 bits back; go cry about it.
•Single Operator FM Synthesis: Full control over the parameters including envelopes,
multipliers, rate scalings, tunings, gates, and internal LFO modulation.
•Feedback: Feedback into the operator one for interesting timbres or total wave destruction
and noise.
•Looping Envelopes: Transform the one-shot envelope generator into a looping AD envelope.
•Low-Frequency Oscillator: A shared low-frequency sine oscillator controls amplitude mod-
ulation and frequency modulation of each operator.
•Mono Output: The original YM2612 was stereo, but only because it had six channels of
synthesis. Mini Boss is a monophonic voice so there is no built-in stereo processing.
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KautenjaDSP Mini Boss v2.0.0
Panel Layout
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1 Envelope Generator
The envelope generator section provides control over the envelope generator parameters for
each of the four operators on the module. Figure 1 depicts the stages in the envelope generator,
where
•Total Level (TL) is the highest amplitude of the envelope generator. A change of one unit is
about 0.75dB;
•Attack Rate (AR) is 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;
•Decay Rate (D1R) is the angle of initial amplitude decrease from the highest point in the
envelope generator;
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KautenjaDSP Mini Boss v2.0.0
•Total Level 1 (T1L): The amplitude where the second decay stage starts;
•Sustain Rate (D2R) is the angle of secondary amplitude decrease. This will continue indefi-
nitely unless key off occurs; and
•Release Rate (RR)is the final angle of amplitude decrease, after key off.
Figure 1: An illustration of the stages in the envelope generator.
The Rate Scale parameter controls the amount of key-scaling that occurs for the envelope
generator parameters ∈ [0 , 3], i.e., the degree to which envelopes become shorter as frequen-
cies become higher. For example, high pitched notes on a piano fade much more quickly than
the low pitched notes.
The Loop switch causes the envelope generator to enter a looping LFO mode when pointing
up. When pointing down, the envelope generator is triggered by gate signals to the GATE port.
The envelope generator can be re-triggered (i.e., triggered during a sustained note) using the
TRIG port.
2 Operator Control
The operator control section provides control over the synthesis parameters of the operator,
namely,
•Frequency is the frequency offset for the operator. For standard FM sounds, all operators
should be tuned to harmonically related frequencies. Individual operators with different
frequencies is a special mode of the 3rd voice on the Yamaha YM2612 that can produce
some weird and bizarre sounds;
•LFO is the rate of the internal low frequency oscillator ∈ [0 , 7] with frequency values mapped
by Table 1. The LFO is used for both amplitude and frequency modulation of the individual
oscillators. When an input is patched to the LFO input, LFO frequencies can be selected in
increments of 1V;
Table 1: Frequencies of the low-frequency oscillator.
Knob Position 01234567
Frequency (Hz)3.98 5.56 6.02 6.37 6.88 9.63 48.1 72.2
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KautenjaDSP Mini Boss v2.0.0
•LFO Frequency Modulation determines the amount of frequency modulation applied to the
operator by the global LFO ∈[0,7];
•LFO Amplitude Modulation determines the amount of amplitude modulation applied to the
operator by the global LFO ∈[0,3];
•FM polarizes and attenuates inputs to the FM port;
•Multiplier is an integer multiplier for the frequency of the operator. MUL ranges from 0to 15,
and multiplies the overall frequency, with the exception that 0results in multiplication by 1
2;
•Feedback controls the amount of feedback for operator 1 ∈ [0 , 7]. When an input is patched
to the FB input, feedback levels can be selected in increments of 1V; and
•Volume controls the output volume level from the synthesizer as an unsigned 7-bit multiplier.
3 Envelope Generator Ports
Each envelope generator parameter has an associated input port. The CV to each port is
quantized uniformly from [ − 8 , 8] V continuous voltage to the discrete range of the associated
parameter. Control voltages are indicated by the LED lights on the slider for the associated
parameter. Positive (negative) voltages result in a green (red) light that increases in brightness
as the voltage increases in magnitude.
4 Voice Ports
•GATE input goes high at 2 V and triggers the envelope generator on the operator. Figure 1
illustrates how the envelope generator interprets key on and key off events in the gate
signal;
•RTRG input goes high at 2 V and re-triggers the envelope generator on the operator if the
gate is high;
•VOCT input provides exponential control for the oscillator’s frequency offset from the base
frequency determined by the Frequency knob;
•FM input allows for an external frequency modulation signal to be applied to the operator in
addition to the feedback;
•VOL input controls the volume level output from the module. When an input is patched to the
port, the VOL knob acts as an attenuator for the signal on the port; and
•OUT provides the monophonic output from the synthesizer ∈[−5,5]V.
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KautenjaDSP Mini Boss v2.0.0
Data Sheet
Type Oscillator / Synth voice
Size 16 HP Eurorack
Depth NA
Power NA
+12Vdraw (mA) 0 mA
−12Vdraw (mA) 0 mA
+5Vdraw (mA) 0 mA
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KautenjaDSP Mini Boss v2.0.0
References
Various (1992). Genesis Sound Software Manual. Sega Corporation.
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