mikroElektronika BassBoy User manual
tm
assBoyB
Monophonic digital MIDI controlled bass synthesizer
Manual
MIDI Device
POWERED BY:
CREATED BY:
Aleksandar Krsti @ć
BassBoy
BassBoy is a monophonic digital MIDI controlled bass synthesizer. Device receives all information via MIDI input ( connector).
Sampling frequency is 31.25KHz which generates audio range up to 15.625Khz. Although it's based on 8-bit processor, the signal
processing inside the unit is 16-bit. The unit consists of oscillator which generates SAW & SQUARE WAVE using 16-bit band-limited
wavetables, thus making the number of harmonics limited. After that, the signal itself goes through a simple implementation of MOOG
filter, whose frequency range is chosen by MIDI commands and which is affected by the level of the envelope. The filtered signal then
comes to the controlled amplifier, which creates the signal shape, and in the end through DAC (WM8762) and pre-amp circuit goes to the
audio jack 6.35mm. The unit is mono, and 6.35mm jack is also used as carrier for the circuit board itself.
MIDI IN
It is crucial that the power supply unit connected to the BassBoy ( connector) is within specifications : +10V to +13V max. MIDI
channel and the note interpretation mode (from now on, refered to as connector) must be chosen before turning on the
unit. The location of the jumpers for choosing MIDI channel and the note interpretation mode is shown on the fig1-3.
PS
CH&MODE
IMPORTANT!!!
BassBoy
MikroElektronika
Figure 1-1: BassBoy
Figure 1-2: Wiring diagram
Low Current LEDS or
LEDS with mcd>200
AACC
POWER
ON
MIDI
RECEIVE
-
+
POWER SUPPLY
INPUT, DC
+10V ... +13V max
MIDI INPUT
DIN5 Female Connector
Front View
45
Audio Output
MIDI control
Selection of SAW or SQUARE wave is done via Program Change, where Program 1 is SAW wave and Program 2 is SQUARE wave, then
sequentially repeats SAW wave as Program 3, SQUARE wave as Program 4 and so on until Program 128. The unit has two ways of
interpretation of received MIDI notes: SEQUENCER MODE and LIVE MODE. Interepretation mode is selected via jumper located on
connector labeled as “CH&MODE”, while reproduced notes are within range from MIDI note 24 to MIDI note 72 (C1 – C5). The unit
doesn't support MIDI pitch change control. Duration and level of envelope only affects the filter. In case that note has accent, then it also
affects the controlled amplifier.
SEQUENCER MODE is mode in which the way of playing current note depends on the way the last note was played. The way of
playing the note is defined by it's velocity, which is shown in this table:
Velocity 0 = NOTE OFF . It has the same meaning as a standard MIDI message $80 note $00. This defines end of duration of
audibility (GATE) of the same note.
Velocity 1 - 16 = NOTE OFF. Note is being turned off, unless the previous note had a SLIDE function, in which case it lasts as long as the
GATE of the same note.
Velocity 17 - 32 = NOTE OFF + SLIDE. Similar to the previous case, but this time note stays on until the next note.
Velocity 33 - 48 = NOTE ON. Duration of the note is defined by the GATE. It turns the note on and triggers the envelope, but it is
applied only if the previous note doesn't have SLIDE turned on ( portamento, gradual slide from previous note to current note). If the
previous note had SLIDE turned on, then envelope wouldn't be triggered and only SLIDE effect would be executed. Duration of the
envelope is defined by MIDI command CC 57.
Velocity 49 - 64 = NOTE ON + SLIDE. Duration of the note is until next note and is not defined by GATE. It turns the note on and
triggers the envelope, but it is applied only if the previous note doesn't have the SLIDE turned on. If the previous note had the SLIDE
turned on, then envelope wouldn't be triggered and only the SLIDE effect would be executed. Duration of the envelope is defined by
MIDI command CC 57.
Velocity 65 - 80 = NOTE OFF + ACCENT. Same as NOTE OFF. Left for compatibility reasons.
Velocity 81 - 96 = NOTE OFF + ACCENT + SLIDE. Same as NOTE OFF + SLIDE. Left for compatibility reasons.
Velocity 97 – 112 = NOTE ON + ACCENT. Duration of the note is defined by the GATE. It turns the note on and triggers the
envelope, but it is applied only if the previous note doesn't have SLIDE turned on. If the previous note had SLIDE turned on, then
envelope wouldn't be triggered and only SLIDE effect would be executed. Duration of an envelope is a constant ~250mS. Value of
the accent is added to the level value of the note. Accent is defined by the MIDI command CC 58.
Velocity 113 - 127 = NOTE ON + ACCENT +SLIDE. Duration of the note is until next note and is not defined by the GATE. It turns
the note on and triggers the envelope, but it is applied only if the previous note doesn't have the SLIDE turned on. If the previous
note had SLIDE turned on, then envelope wouldn't be triggered and only SLIDE effect would be executed.Duration of the envelope
is a constant ~250mS. Value of the accent is added to the level value of the note. Accent is defined by the MIDI command CC 58.
BassBoy
MikroElektronika
Figure 1-3: CHANNEL & MODE JUMPER POSITION
LEGEND: JUMPER FREE
MIDI CH1
MIDI CH2
MIDI CH3
MIDI CH4
MIDI CH5
MIDI CH6
MIDI CH7
MIDI CH8
MIDI CH9
MIDI CH10
MIDI CH11
MIDI CH12
MIDI CH13
MIDI CH14
MIDI CH15
MIDI CH16
MIDI CH1
MIDI CH2
MIDI CH3
MIDI CH4
MIDI CH5
MIDI CH6
MIDI CH7
MIDI CH8
MIDI CH9
MIDI CH10
MIDI CH11
MIDI CH12
MIDI CH13
MIDI CH14
MIDI CH15
MIDI CH16
LIVE MODE with CHANNEL SELECTION SEQ MODE with CHANNEL SELECTION
LIVE MODE is a mode in which the duration of the note is defined by the GATE. VELOCITY defines the way notes are being played:
Velocity 0 – 100 = NOTE ON. Triggers the envelope. Duration of the envelope is defined by the MIDI command CC 57.
Velocity 101 – 127 = NOTE ON + ACCENT.Triggers the envelope. Duration of the envelope is constant ~250mS. Value of the accent is
added to the level value of the note.Accent is defined by the MIDI command CC 58.
FunctionAUTO-SLIDE is constantly turned on only in this mode and is triggered when notes overlap.
This mode is more suitable for playing over MIDI keyboard, as well as controlling the unit via MIDI file, while sequencer mode is more
suitable for work with older sequencers that don't have note overlap function, but can also be used for work with MIDI files (easier input of
sequences from other bass lines).
MIDI CONTROL CHANGE MESSAGES
Midi CC 7 Volume.
idi CC 53 Filter Pre-Gain.
Midi CC 54 Cut-Off.
Midi CC 55 Resonance.
Midi CC 56 Envelope modulation.
Midi CC 57 Envelope Decay.
Midi CC 58 Accent.
Midi CC 59 Distort Gain.
Midi CC 60 Cut-Off step.
Midi CC 123 ALL NOTES OFF.
(default value = 127).A standard defined CC message – output volume level. In 127 steps of 0.5dB, where value 0 is
value for MUTE, and value 127 = 0db (relative) maximum output level. Steps are logarithmic, and transition between the steps is linear for
a smooth transition.
(default value = 0). Controls input signal level into the filter. Low value, hard resonance, but soft sound.
Higher value, lower resonance, but harder sound. Values from 0 to 127.
(default value = 0). Controls cutting frequency of the filter. Works in conjunction with command CC 56. Values from 0
to 127.
(default value = 0). Controls the signal level brought from output to input of the filter. Feedback. Values from 0 to
127. Value 112 is optimal, while 127 is near the self oscillation of the filter.
(default value = 0). Controls the signal envelope level brought to the control level of the filter and
affects the cutting frequency of the filter. Envelope is logarithmic. Values from 0 to 127.
(default value = 0). Controls duration of the note without accent. Values from 0 to 127. Duration from
~250mS to ~2s.
(default value = 0). Controls intensity of the accent on notes with accent. Values from 0 to 127. When in CC 55
resonance is minimum value, envelope which comes to filter is logarithmic, but when CC 55 resonance is at maximum value, envelope is
softened logarithmic and sounds like a little ducky effect.
(default value = 4, gain x2). Controls level of the sound coming out of the controlled amplifier. Values from 0 to
127. Where values from 0 – 3 mean direct throughput without amplification, and rest of the values are MIDI Value 4 – 127 / 2 =
amplification 2x to 63x. It leads to hard cutting off of top of the signal, depending on the value (HARD CLIPPING DISTORTION) and
makes distortion of the sound.
(default value = 30) Controls fluency of the change to the cut-off filter, that is speed of step change to the MIDI
command CC 54. Values 0 to 127.
Used as PANIC command. In case the note didn't get turned off , sending this command
note is turned off instantly. Value doesn't affect execution of the command.
M
for some reason
Electrical data:
Power supply : +10V to +13V max, DC
Current consumption: max. 100mA
MIDI input separated by opto-coupler.
Maximum output voltage: approx. 2.2VRMS = 6.2V peak-to-peak output impedance 1MOhm, approx. 1.95VRMS = 5.5V peak-to-peak
output impedance 10kOhm (measured with generated SINE wave directly towards DAC, measured on the 6.35mm jack). Output
impedance > 10KOhm.
Notes are in range from 32.70Hz to 523.25Hz, that is MIDI note 24 to MIDI note 72 (C1 – C5) (maximum deviation +/-1.5 cents).
BassBoy
MikroElektronika
1K
R2
GND
10uF
C6
tant 16V
GND
MIDI CHANNEL & MODE
100K
R8
1K
R7
GND
10K
R4
+3.3V
220
R3
1
2
CN3
MIDI IN
1
2
3
6
5
4
OPTO1
CNY17-3
330u
C11
330u
C14
100nF
C12
100nF
C13
GND
ADC1/PA1 41
ADC0/PA0 40
ADC2/PA2 42
ADC3/PA3 43
ADC4/PA4 44
ADC5/PA5 1
ADC6/PA6 2
ADC7/PA7 3
(SPI)SCK/PC7 17
(SPI)MISO/PC6 16
(SPI)MOSI/PC5 15
(SPI)SS/PC4 14
TXD0/PC3 13
RXD0/PC2 12
(TWIC)SCL/XCK0/PC1 11
(TWIC)SDA/PC0 10
PB3/ADC11
7
PB2/ADC10
6
PB1/ADC9
5
PB0/ADC8
4
PD7/CLKOUT/SCK(SPID)
27
PD6/MISO(SPID)
26
PD5/MOSI(SPID)
25
PD4/SS(SPID)
24
PD3/TXD1
23
PD2/RXD1
22
PD1/XCK1
21
PD0
20
PE3
33
PE2
32
PE1/SCL(TWIE)
29
PE0/SDA(TWIE)
28
GND
8
GND
18
GND
30
GND
38
VCC 9
VCC 19
VCC 31
AV C C 39
RESET/PDI_CLK 35
PDI_DATA 34
PR1/XTAL1
37 PR0/XTAL2
36
U1 ATXMEGA32D4
Gnd
+3.3V
GND
100nF
C1
100nF
C8
GND
+3.3V
100nF
C7
GND
+3.3V +3.3V
10K
R1
MIDI RX
DAC CLK
DAC DATA
DAC WS
MIDI RX
1
2
3
CN2
GND
CLOCK
32.000MHz
SELECT
GND
1IN
3OUT 2
OUT 4
U4
TLV1117-3.3
GNDGND GND GND
+3.3V
PDI_PGM
GND
DC POWER
SUPPLY
1
2
CN4
PS
OUT
WT
TN
RN
WR
WS
SN
J1
6.35mm JACK
10K
R6
3K3
R5
1K5
R9
+3.3V
GND
15pF
C16
15pF
C15
GND GND
12
CR1
8.000MHz
1
2
3
CN5
LEDS
MIDI DATA
MIDI DATA
+V 4
OUT 3
NC
1
GND
2
OSC1
8.000MHz
GND
OPTIONAL EXTERNAL CLOCK
+3.3V
DAC DATA DIN
1
BCKIN
2
LRCIN
3
MCLK
4
VOUTR 8
VDD 7
GND
6
VOUTL 5
U3
WM8762
DAC CLK
DAC WS
GND
GND
100nF
C3
+3.3V
10uF
C4
tant 16V
GND
CLOCK
4
CLK
3
D
2
1
Q5
Q6
VDD 14
GND 7
CLR
PR
U2A
MC74HC74AD
VDD 14
GND 7
10
CLK
11
D
12
13
Q9
Q8
CLR
PR
U2B
GND
16.000MHz
32.000MHz
+3.3V
GND
+3.3V
Q1
BC550C
Q2
BC560C
3K3
R10
100
R11
10uF
C5
tant 16V
+3.3V
+VCC
10K
R12
GND
100K
R13
1K
R14
10uF
C9
tant 16V
GND
D3
+VCC
100nF
C2
GND
D1
1N4148
D4 D5 D6 D7
D2
D2 ... D7 = 1N4007
100K
R15
GND
GND
GND
1 2
3 4
5 6
7 8
910
CN1
100nF
C10
GND
+3.3V
GND
100nF
C17
2SC2240
or
or
2SA970
AUDIO OUTPUT
BassBoy
MikroElektronika
Figure 1-4: BassBoy MIDI device schematic
Table of contents
