GRP Synthesizer A4 User manual

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Grp!A4!Synthesizer!
Owner’s!Manual!
V.!1.09!
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S
VC LOW FREQUENCY OSCILLATOR 1
MIXER
EXT IN - ENV FOLL
CV OUT 0/+8V
CONNECTIONS
CLK IN 0/+5V CLK OUT 0/+5V
LEFT/24db RIGHT/12db
PHONES
GATEIN 0/+5VCV IN 1V/Oct
CV OUT 1V/Oct CV IN 24db
AMT
2
56
7
8
9
10
4
3
1
0
0+1
+2
+3
+4
-1
-2
-3
-4
PW
-5 +5
SOURCE CV
VOLTAGE CONTROLLED AMPLIFIER
RELEASEDECAY SUSTAIN
LEVEL
ATTACK
GATE
SEQ
ENVELOPE GENERATOR 2
AM LFO1
OFF
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
STEREO MAIN
MASTER VOLUME
56
7
8
9
10
4
3
2
1
0
GATE AUTO
10
CV VCA
EG2 HOLD
EXT CV
SAMPLE & HOLD - NOISE
RUN/STOP RESET LOOP ON/OFF
GATE OUT 0/+5V
Grp Synthesizer A4
®
KYBD
VOLTAGE CONTROLLED FILTER
12 db STATE VARIABLE FILTER24 db LOW PASS FILTER
RESONANCE
56
7
8
9
10
4
3
2
1
0
FREQUENCY
56
7
8
9
10
4
3
2
1
0
ROUTING
24db
12db SER
PAR
DIST/LEVEL
AMT
RESONANCE
56
7
8
9
10
4
3
2
1
0
AMT FM3
AMT
MODE
12db HP
6db BP
NOTCH
12db LP
AMT FM3
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
AMOUNT EG
OVERLOAD
6db
12db
24db
18db
SLOPE
FM2 LFO1
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
ATTACK
GATE AUTO
SUSTAINDECAYHOLD RELEASE
LEVEL
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
AMOUNT EG
56
7
8
9
10
4
3
2
1
0
VELOCITY EG
OVERLOAD
KYBD TRK
REVNOR
SEQ
ON
FREQUENCY
56
7
8
9
10
4
3
2
1
0
10
ENVELOPE GENERATOR 1
NOR REV
REV
NOR
REV
NOR
SEQ
KYBD/S&H
EXT IN
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
PHASEPHASE
FM1 FM1
AUDIO PATH
DIROUT
OFF
DIST/LEVEL
DIST DIST
FM2 LFO1
LOOP
ROW ATRNP
CVIN CLK MOD AUDIOEXTIN
OFF
ROW BROW A ROW A + B
TIME
GATE LOOP
KYBD/S&H
EXT IN
INPUT GAIN
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
FREQUENCY
NOISE
56
7
8
9
10
4
3
2
1
0
RING MOD
VCO2 x VCO3/EXT IN
56
7
8
9
10
4
3
2
1
0
VCO 3 EXT INPUT
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
SUB 2VCO 2
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
VCO 1 SUB 1
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
AUTO PAN
GATE
THRESHOLD
56
7
8
9
10
4
3
2
1
0
INT LFO1
OFF
WHITE
PINK
INT
LFO 1
OFF
GATE SEQ
MIDI
SYNC
CLOCK
2
56
7
8
9
10
4
3
1
0
GLIDE
2
56
7
8
9
10
4
3
1
0
OFF
GATE
CLOCK EG
AUTO
VCO 1
NOISE
AFT T
S&H
EG 2
LFO 1
VCO 2
LFO 2
VCO 3
SOURCE
MOD W
ENV FOLL
VCO 1
NOISE
AFT T
S&H
EG 2
LFO 1
VCO 2
LFO 2
VCO 3
SOURCE
MOD W
ENV FOLL
CVIN 12db
NOR
PHASE
REV
WAVEFORM
ENV FOLL
SHAPING SELECT
EG 1
EG 2
SEQ A+B
AFT T
SEQ A
SEQ B
HOLD
MOD W
S&H
LFO 2
ENV FOLL
LFO 2 SEQ A
MOD W
EG 1
S&HAFT T
KYBD
EG 2
SEQ A+B
SEQ B
LOW FREQUENCY OSCILLATOR 2
VCO PWM VCF 24db/12db
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
FREQUENCY WAVEFORM
ENV
FOLL
NGEG 1
EG 2
VCO 1 VCO 2 VCO3
S&H
EXT IN
SHAPING SELECT
AFT T
MOD W
HOLD
T
TUNING - MIDI
RTRGHOLD
MASTER TUNE
0+1
+2
+3
+4
-1
-2
-3
-4
5
b-5
+#
0+1
+2
+3
+4
-1
-2
-3
-4
TUNE 5
+#
5
b-
OCTAVE
64'
32'
16' 8' 4'
2'
WAVEFORM
0+1
+2
+3
+4
-1
-2
-3
-4
FINE 5
+#
5
b-
VOLTAGE CONTROLLED OSCILLATOR 1
OCTAVE
64'
32'
16' 8' 4'
2'
WAVEFORM
VOLTAGE CONTROLLED OSCILLATOR 2
LFO 1
2
56
7
8
9
10
4
3
1
0
AMT
2
56
7
8
9
10
4
3
1
0
VOLTAGE CONTROLLED OSCILLATOR 3
0+1
+2
+3
+4
-1
-2
-3
-4
TUNE 5
+#
5
b-
OCTAVE
64'
32'
16' 8' 4'
2'
0+1
+2
+3
+4
-1
-2
-3
-4
FINE 5
+#
5
b-AMT
2
56
7
8
9
10
4
3
1
0
LFO 1
2
56
7
8
9
10
4
3
1
0
WAVEFORM
AMT
2
56
7
8
9
10
4
3
1
0
LFO 1
2
56
7
8
9
10
4
3
1
0
SUB -2
SUB -1
LIN
EXP
SYNC VCO1
ON
KYBD
OFF
SUB -2
SUB -1
LIN
EXP
LIN
EXP
RM IN SEL
EXT IN
FM1 SOURCE
VCO 2
NOISE
VCO 3
EG 1
AFT T
LFO 1
LFO 2
S&H
VEL
EG 2
MOD W
PW
2
56
7
8
9
10
4
3
1
0
PWM
2
56
7
8
9
10
4
3
1
0
PWM
2
56
7
8
9
10
4
3
1
0
PW
2
56
7
8
9
10
4
3
1
0
LFO 1
LFO 2
56
7
8
9
10
4
3
2
1
0
PORTAMENTO BEND AMOUNT
56
7
8
9
10
4
3
2
1
0
ON
REV
NOR
SYNC VCO1
ON
PHASE
PHASE
REV
NOR
PHASE
VCO1 OFF
KYBD
OFF
MANUALPROGR
EDIT GATE ON
KYBD
OFF
MIDI ACT
VCO 3
REV
NOR
PW
2
56
7
8
9
10
4
3
1
0
PWM
2
56
7
8
9
10
4
3
1
0
LFO1
LFO 2
LFO1
LFO 2
+3
0+1
+2
+4
-1
-2
-3
-4
TUNE 5
+#
5
b-
0+1
+2
+3
+4
-1
-2
-3
-4
FINE 5
+#
5
b-
440Hz
56
7
8
9
10
4
3
2
1
0RANGE
MID
SLOW
FAST
VCA
56
7
8
9
10
4
3
2
1
0
RUN/STOP
SEQUENCER 8 x 2
56
7
8
9
10
4
3
2
1
0
X4
X2
QNT B
OFF
ON
QNT A
OFF
ON
RANGE A
X8
RANGE B
X4
X2
X8
GLIDE A
GLIDE B
16X1 8X2
MODE
56
7
8
9
10
4
3
2
1
0
STEP REPEAT
N,N,N+1,N
OFF
X2
X3 X4 N,N+1
N,N+1,N
CLOCK
OFF
RESETSTEP ADV
56
7
8
9
10
4
3
2
1
0
INT
LFO 1 EXT
CLOCK SELECT
A
1 2 3
PWM SEQ ENABLE
A+B
BB
FLT SEQ ENABLE
BB
AA+B
24db 12db
SEQUENCER MODE
FW
BW
FW/BW
PNDL
ALT
RND
TRG
56
7
8
9
10
4
3
2
1
0PW
123
VCO SEQ ENABLECV SEQ CLOCK
HOLD
OFF ON
LOOP
OFF ON
OFF OFF
A
B
LEVEL LEVEL
TIME
SEND MODULATION
NOISE
INPUT SOURCE
VCO 2
VCO 1
LFO 1
LFO 2
EXT IN
OVERLOAD
FREQUENCY
56
7
8
9
10
4
3
2
1
0
GATE
CLOCK / TRNP SEQ
B
A
GATE
ON
GATE
ON
END STEP
01
SKIP
NOR
GATE END STEP
ON SKIP
NOR
GATE END STEP
ON
03
SKIP
NOR
GATE END STEP
ON
04
SKIP
NOR
GATE END STEP
ON
05
SKIP
NOR
GATE END STEP
ON
06
SKIP
NOR
GATE END STEP
ON
07
SKIP
NOR
GATE END STEP
ON
08
SKIP
NOR
END STEP
09
SKIP
NOR
GATE END STEP
ON
10
b#
SKIP
NOR
GATE END STEP
ON
11
SKIP
NOR
GATE END STEP
ON
12
SKIP
NOR
GATE END STEP
ON
13
SKIP
NOR
GATE END STEP
ON
14
SKIP
NOR
GATE END STEP
ON
15
SKIP
NOR
GATE END STEP
ON
16
SKIP
NOR
#
00 0 0
0
0
0
0
0
0
bb#
0
02
b#b#b#
0
b#b#
0
b#
0
b#
0
b#b#
0
b#
0
b#b#b#
CLOCK DIVIDER
/3
/2
/1
1/1
/4
1/2T
1/2
/6
/8
1/4T
1/81/4
/12
1/8T
/16
/32
MONO
FM1 SOURCE
VCO 1
NOISE
VCO 3
EG 1
AFT T
LFO 1
LFO 2
S&H
VEL
EG 2
MOD W
FM1 SOURCE
VCO 1
NOISE
VCO 2
EG 1
AFT T
LFO 1
LFO 2
S&H
VEL
EG 2
MOD W
FLT
VCO 3
MAIN
CVIN VCA/AFTT
MIDI
GATEOUT 0/+5V
1/16
1/32
ROWA+ BTRNP
MIDI
BA+B
AA
!
!
!

Grp A4 Synthesizer – Owner’s Manual
!
!"

Grp A4 Synthesizer – Owner’s Manual
!
#"
CONTENTS!
"
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"
31'(')"0+-15,6"0(-("
" 417"0+-15,"0(-("('3,&*%2,"
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"
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"
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" 417"0+-15,"9!"=7"43%3,"8%&(%75,"*(53,&"
" 417"0+-15,",'8,5+.,"),',&%3+&"9"
"
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" 417"0+-15,",'8,5+.,"),',&%3+&"!"
"
0+-15,"%13+".%'"
"
0+-15,"43,&,+"0%('"
"
0+-15,"82"5+$"*&,>1,'2?"+42(55%3+&"9"
"
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"
0+-15,"4%0.5,";"@+5-"
"
0+-15,",<3"('"6",'8"*+55"
"
0+-15,"43,."4,>1,'2,&"AB!"
" 43,.".%&%0,3,&4"
" &+$"%";"7".%&%0,3,&4"
" &+$"%";"7"&+13(')4"
"4,>1,'2,&".%&%0,3,&4"
"
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"
&,%&".%',5"2+'',23(+'4"
!
!

Grp A4 Synthesizer – Owner’s Manual
!
/"
!"#$%&%'()*+),+#)*,)&-('.+
+
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"#!$%&&'('!"'((%))*+
+&!,-.',!/-0/-&-()')*1-!%2!3'(*2'4)5/-/+/&0+1.*'2"1(3"&+++
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+
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+
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#7N:M+/&0+%D+
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1Q*M!!&--!/-'/!0'(-,!,':-,!
+
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+
"
!
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^?57?I69:8:+:++
#69:8:+N5+#799:8I57<+%K@785@_+!7T6?6;5<+'85SK?6;5!
!

Grp A4 Synthesizer – Owner’s Manual
!
C"
Warranty
F=-! .5'/'()--! )-/3&! ,*&)-6! *(! 25,,! *(! )=-! 05/4='&-! './--3-()#! '/-! 1',*6! %(,E! *2! )=-! &E()=-&*>-/! *&!
5&-6!*(!)=-!4%(6*)*%(&!%2!*()-(6-6!5&-@!
F=-!%(,E!-G4-0)*%(&!)%!)=-!3'*()-('(4-!6-&4/*:-6!*(!)=-!4='0)-/@!H+"IFJI+IAJ!'(6!0-/2%/3-6!
K*)=! )=-! 0/%4-65/-&#! '(E! /-0'*/&! %/! 3%6*2*4')*%(&! )%! )=-! 35&*4',! *(&)/53-()! %/! 4%30'(*-&! (%)!
'5)=%/*>-6!:E!)=-!5&-/!6-)-/3*(-&!)=-!6-4'E!%2!)=-!K'//'()E@!
F=-! K'//'()E! 6%-&! (%)! -G)-(6! )%! 6'3'.-! 4'5&-6! :E! 3',0/'4)*4-! %/! (-.,*.-(4-! *(! )=-! 5&-! %2! )=-!
&E()=-&*>-/#!%/!:E!0%%/!3'*()-('(4-!%/!2'*,5/-@!
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F=-!0/%654)&!K-!&-,,!'/-!4%1-/-6!:E!K'//'()E!'&!)%!)=-!&E()=-&*>-/!)%!)=-!2%,,%K*(.!4%(6*)*%(&9!
L!
F=-!K'//'()E!*&!1',*6!2%/!'!0-/*%6!%2!M!N)K%O!E-'/&@!
M!
LO F=-! 3'(52'4)5/-/! 5(6-/)'P-&! )%! /-0,'4-#! ')! *)&! 6*&4/-)*%(! 0'/)&! 3',25(4)*%(*(.! %/! *(4%//-4),E!
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SO F=-! 3'(52'4)5/-/! '&&53-&! (%! /-&0%(&*:*,*)E! 2%/! '(E! 6*22*45,)*-&! )=')! 3'E! '/*&-! *(! )=-! 5&-! %/!
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V!
DO +/-! -G4,56-6! 2/%3! )=-! K'//'()E! 4%1-/! 0'/)&! &5:W-4)! )%! K-'/#! &54=! '&! 4%((-4)%/&#!
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F=-! 3'(52'4)5/-/! *&! (%)! ,*':,-! 2%/! '(E! 6'3'.-! )%! 0-/&%(&#! '(*3',&! %/! 0/%0-/)E! /-&5,)*(.! 2/%3!
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8*'![%/3-,,%#!LV!!H%()-0%/>*%!A')%(-!\\\S\!]!$H!
7@"8+!L\UXLUQL\\V!!
*(2%^./0&E()=-&*>-/@*)!=))09RR=))09RRKKK@./0&E()=-&*>-/@*)!
!
!
!

Grp A4 Synthesizer – Owner’s Manual
!
D"
T5-!)%!)=-!4%()*(5%5&!-1%,5)*%(!%2!0/%654)&#!2-')5/-&!'(6!6-&*.(!%2!)=*&!3%6-,!3'E!
4='(.-!K*)=%5)!(%)*4-@!
!
ID Labels
F=-! Y$7! ZE()=-&*>-/! +S! *&! -_5*00-6! K*)=! '(! *6-()*2*4')*%(! 0,')-! %(! K=*4=! )=-E!
/-0%/)-6! )=-! *6-()*2*4')*%(! %2! )=-! 6-1*4-! '(6! )=-! 3'*(! )-4=(*4',! 6')'! /-,')*(.! )%!
0%K-/!&500,*-&@!
!
!
+
+
`%&*(*/a+
+
+
')+-%(*'%(*+'2"+(*'"/&('.+b),+%$$+#)-0)*"*'1+
!"4(#"+(1+"11"*'(%$+#)-0$.+
10"#(,(#%'()*1+$(1'"!+)*+'2"+$%c"$[+
+
!
!
!
+
+
!%*/"&+
+
+
%##"11+')+0&)'"#'"!+)&+0%&'1+),+'2"+#$)1"!+
/&0+1.*'2"1(3"&+%D+-^1'+c"+-%!"+)*$.+
,)&+)0"&%'()*1+%*!+-%(*'"*%*#"+)*$.+
%^'2)&(3"!+0"&1)**"$[+
+
!
!

Grp A4 Synthesizer – Owner’s Manual
!
E"
Operation
A%((-4)!)=-!0%K-/!4%/6!*()%!)=-!"JA!&%4P-)!%(!)=-!/-'/!0'(-,#!3'P*(.!&5/-!)=')!)=-!
1%,)'.-!'(6!2/-_5-(4E!4%//-&0%(6!)%!)=-!,':-,@!
"(&-/)!)=-!0,5.!*()%!)=-!K',,!%5),-)@!
F=-!0%K-/!;JT!%(!)=-!2/%()!0'(-,!*(6*4')-&!)=-!4%//-4)!25(4)*%(*(.!%2!*(6*1*65',!
&-4)*%(&!%2!)=-!7Z`@!
!
Handling and cleaning
F=-!Y$7!+S!6%-&!(%)!(--6!'(E!3'*()-('(4-!)%!)=-!*()-/(',!4*/45*)&@!
F%!4,-'(!)=-!4%()'*(-/!*&!&*30,E!'!4,-'(!4%))%(!4,%)=!'(6!&,*.=),E!6'30@!F=-!0'*()!*&!
/-&*&)'()! )%! (%/3',! 4,-'(*(.! 0/%654)&#! K*)=! )=-! -G4-0)*%(! %2! &)/%(.! &%,1-()&!
N:-(>-(-#!'4-)%(-#!6*,5-()&!*(!.-(-/',#!-)4@@O@!
Troubleshooting
a-/-!'/-!&%3-!0/%:,-3&!E%5!3*.=)!-(4%5()-/!K=*,-!5&*(.!)=-!Y$7!ZE()=-&*>-/!+S@!
Z%3-!4'&-&!'/-!-'&E!)%!&%,1-#!K=*,-!%)=-/&!/-_5*/-!)=-!*()-/1-()*%(!%2!&0-4*',*>-6!
0-/&%((-,!%/! )=-!3'(52'4)5/-/@!T%! (%)!=-&*)')-!)%!4%()'4)!5&! K*)=!'(E!_5-&)*%(&@!
b-!'/-!=-/-!)%.-)=-/!)%!&%,1-!-1-/E!0/%:,-3@!
c:O78:+ I7??:I@5?T+ @J:+ /&0+ %D<+ 96d:+ LK8:+ @J6@+ @J:+ U7;@6T:+ 6?N+ IK88:?@+
?:I:LL68]+@7+S:+I79A6@5S;:+R5@J+@J:+IJ686I@:85L@5IL+7O+@J:+N:U5I:[+
Y$7! ZE()=-&*>-/! 6*&4,'*3&! '(E! ,*':*,*)E! 2%/! 3*&5&-! %2! )=-! Y$7! ZE()=-&*>-/!
&E()=-&*>-/!+S@+
!'J:+/&0+%D+N7:L+?7@+I79:+7?+X6;;+$"!L+68:+7OOY[+A=-4P!2%/!'(E!(-)K%/P!
*(! )=-! &%4P-)@! A=-4P! )=-! 0%K-/! 4%/6@! A=-4P! )=-! 25&-! *(&-/)-6! *()%! )=-! "JA!
&%4P-)! %(! )=-! /-'/! 0'(-,@! "2! )=-! Y$7! +S! &)*,,! 6%-&! (%)! ,*.=)#! 4%()'4)! Y$7!
ZE()=-&*>-/@!
!)?:+78+978:+$"!L+7?+@J:+O87?@+N7:L+?7@+;5TJ@+KA+6?N+@J:+L]?@J+N7:L?e@+
L7K?NL[!A%()'4)!Y$7!ZE()=-&*>-/@!
Fuse change
F=-!%(,E!5&-/c'44-&&*:,-!25&-!*&!4%()'*(-6!*(!)=-!'00/%0/*')-!0,'4-!*(!25&-!=%,6-/&!
"JA!0%K-/!&%4P-)!%(!)=-!/-'/!0'(-,@!F%!/-0,'4-#!2*/&)!6*&4%((-4)!)=-!0%K-/!4%/6#!
)=-(!/-3%1-!)=-!25&-!=%,6-/!5&*(.!'!&4/-K6/*1-/@!
!
+
+
`%&*(*/+
+
+
#2%*/"+'2"+"f'"&*%$+,^1"+)*$.+`('2+%*)'2"&+),+'2"++
1%-"+'.0"<+#^&&"*'<+!(-"*1()*+%*!+c"2%4()&[+(,<++
%,'"&+%+,(&1'+1^c1'('^'()*<+,^1"+c$)`1+%/%(*<+!)+*)'+%''"-0'+
%+1"#)*!+1^c1'('^'()*g+(*1'"%!<+!(1#)**"#'+'2"+1.*'2"1(3"&+
,&)-+%#+0)`"&+%*!+#)*'%#'+/&0+1.*'2"1(3"&[+
+
+
!
!
!

Grp A4 Synthesizer – Owner’s Manual
!
A"
!
+
+
!%*/"&+
+
+
*"4"&+%''"-0'+')+#2%*/"+,^1"+`('2+!"4(#"+#)**"#'"!++
')+%#+0)`"&+$(*"+
+
+
Important safety warnings
F=-! -(1*/%(3-()',! 0%,*4E! %2! Y$7! ZE()=-&*>-/! ,*3*)&! )%! )=-! 3*(*353! )=-! 5&-! %2!
0%,,5)*(.! 3')-/*',&! N,-'6#! &%,1-()&#! -)4@@O@! `(6-/! 45//-()! ,-.*&,')*%(#! E%5! 35&)!
6*&0%&-!%2!)=-!Y$7!ZE()=-&*>-/!+S!*(!'44%/6'(4-!K*)=!,%4',!/-.5,')*%(&!/-.'/6*(.!
6*&0%&',! %2! K'&)-! -,-4)/*4',! '(6! -,-4)/%(*4! -_5*03-()@! [%/! (%! /-'&%(! )%! ':'(6%(!
)=-! 0/%654)! *(! )=-! -(1*/%(3-()9! '4)*%(#! )=*&#! '! 4/*3*(',! %22-(&-#! '(6! '! &%5/4-! %2!
,%(.!)-/3!0%,,5)*%(@!
"(!%/6-/!(%)!)%!*(45/!)=-!/*&P!%2!-,-4)/*4!&=%4P!'(6!R!%/!*(W5/*-&!E%5!35&)!4'/-25,,E!
2%,,%K!)=-!*(&)/54)*%(&!*(!)=-!3'(5',!'(6!*(!)=-!(%)-&!:-,%K@!
+
+
`%&*(*/+
+
+
')+%4)(!+&(1h+),+"$"#'&(#+12)#h+
%*!+Q+)&+(*\^&.+.)^+-^1'+,)$$)`+
'2"+(*1'&^#'()*1+(*+'2"+-%*^%$+%*!+'2"+*)'"1+c"$)`[+
+
!
F!7+ ?7@+ 7A:?+ @J:+ L]?@J:L5B:8g+ ?:U:8+ 7A:?+ 5@[+ 'J:+ 8:97U6;+ 78+
N5L6LL:9S;]+ 7O+ 6?]+ A6?:;+ 5?U7;U:L+ @J:+ 7A:86@78+ :iA7LK8:+ @7+
A7@:?@56;;]+ J6B68N7KL+ U7;@6T:L[+ ,78+ R78d5?T+ 5?L5N:<+ /&0+ 1]?@J:L5B:8+
6?N+ I7?@6I@+ 7?;]+ jK6;5O5:N+ A:8L7??:;[*7?+ 859K7U:8:+ 6;IK?6+ U5@:+ LK5+
A6??:;;5+:L@:8?5+N:;;e6AA686@7[+
Fk+ !7+ ?7@+ :iA7L:+ @J5L+ 6AA686@KL+ @7+ 865?<+ R6@:8+ LA86]<+ :iI:LL5U:+
975L@K8:<+ U6A78<+ NKL@<+ 9:@6;+ A68@5I;:L+ 78+ 6?]+ 7@J:8+ 96@:856;+ @J6@+ I6?+
A:?:@86@:+5?@7+@J:+U:?@5;6@57?+J7;:L[+
F!7+?7@+AK@+ 7@J:8+7Sl:I@L+5?+ @J:+%#+ A;KT+ 7?+@J:+ 8:68+ A6?:;<+:iI:A@+ @J:+
6AA87A856@:+A7R:8+I6S;:[+
F!7+?7@+:iA7L:+@J5L+6AA;56?I:+@7+J:6@[+
F!7+ ?7@+ :iA7L:+ @J:+ K?5@+ @7+ :iI:LL5U:+ LJ7Id+ 78+ U5S86@57?+ NK85?T+
7A:86@57?[+
Fk+ `J:?+ 5?L@6;;5?T<+ 78+ KL5?T+ 5?+ @J:+ ;7I6;+ J7@+ 6?N+ JK95N+ 6L+ 6+ 8:LK;@+ 7O+
L@786T:+ 78+ @86?LA78@+ 6@+ U:8]+ ;7R+ @:9A:86@K8:L<+ 5@+ 5L+ A7LL5S;:+ @J:+
O7896@57?+ 7O+ I7?N:?L6@57?+ 7?+ @J:+ 7K@L5N:+ 6?N+ 5?L5N:+ @J:+ N:U5I:[+ (@+ 5L+
@J:8:O78:+ ?:I:LL68]+ @7+ R65@+ O78+ @J:+ I7?N:?L6@57?+ N5L6AA:68L+ S:O78:+
@K8?5?T+]7K8+K?5@[+

Grp A4 Synthesizer – Owner’s Manual
!
G"
F%;R6]L+KL:+@J:+A87A:8+6?N+K?N696T:N+A7R:8+I6S;:L[+"LA:I56;;]<+?:U:8++
S8:6d+@J:+I:?@:8+I7?NKI@78+7O+@J:+A5?L+78+L7Id:@L+I7??:I@5?T+@7+:68@J+
@J:+A87@:I@5U:+9:@6;+I6L5?T[+
Fk+%;R6]L+IJ:Id+@J6@+@J:+965?L+A7R:8+5L+I7?L5L@:?@+R5@J+@J6@+8:A78@:N+
5?+@J:+S6Id+7O+@J:+N:U5I:[+
Fk+!7+?7@+7SL@8KI@+@J:+U:?@5;6@57?+J7;:L+7O+@J:+K?5@[+
F(?+ I6L:+ 7O+ L:U:8:+ @JK?N:8L@789L<+ 6U75N+ KL5?T+ @J:+ N:U5I:+ 6?N+
N5LI7??:I@+5@+O879+965?L+6?N+7@J:8+:jK5A9:?@[+
F(O+ @J:+ OKL:+ 5L+ ?7@+ 6+ 8:LK;@+ 7O+ :i@8678N5?68]+ :i@:8?6;+ :U:?@L<+ LKIJ+ 6L+
LKNN:?+ 78+ U57;:?@+ ?:@R78d+ 7K@6T:L<+ L@789L+ :@I[[<+ N7+ ?7@+ @8]+
8:A;6I:9:?@<+SK@+N7+IJ:Id+@J:+K?5@+S]+6+jK6;5O5:N+@:IJ?5I56?[+
F!7+?7@+O78I:+@J:+8K?+7O+@J:+8:TK;6@57?L+S:]7?N+@J:+;595@L[++
!
Notes
!
!
!

Grp A4 Synthesizer – Owner’s Manual
!
9H"
!
FOREWORD!
Thank you for purchasing the Grp Synthesizer A4: this machine will rewards you with
years of sonic satisfactions and, to ensure your instrument will functions properly,
please read this manual.
SOME!WORDS!OF!WISDOM!
Read the following safely tips carefully! You should always observe some basic
precautions when dealing with electronic equipment, for you safety and for safety of
your own equipment.
OPERATING!CONDITIONS!
•Never use the synthesizer under potentially damp/wet conditions such
bathrooms, swimming pools, etc.
•Do not use the instrument in extremely dusty and dirty environments.
•Do not place the instrument near heat sources like radiators.
•Do not expose the instrument to direct sunlight; the wooden cabinet is
varnished with a traditional and trusted procedure, but ultraviolet rays from
sunlight can quickly fade the original wooden colour.
•Do not expose the device to extreme vibrations.
•Save the original crate and boxing for future shipping of the instrument.
POWER!SUPPLY!
•Your Grp A4 Synthesizer is already set for the correct AC powering for your
area. You can read it on the label in the rear panel.
•Unplug the device when you are not using it for longer periods.
•Never touch the plug with wet hands.
•When unplugging the instrument, always grab and pull the plug, never the cable.
OPERATION!
•Although you are a rockstar, NEVER place cans of beer, coke, water (?) or
other potentially spilling liquids on or near the instrument.
•The Grp A4 Synthesizer is an heavy synthesizer: place it on a suitable solid
surface or table.
•The Grp A4 Synthesizer can be very LOUD: please, be careful with the big
volume knob on the lower right of the front panel.
MAINTENANCE!
•Do not open the instrument; do not unscrew the front/rear panels. Inside the
instrument, there aren’t user’s serviciable parts.
PROPER!USE!
•This synthesizer is designed exclusively to produce audio rate frequency signals
for musical purpose. Any other use is prohibited and voids the warranty
extended by Grp Synthesizer. Grp Synthesizer is non liable for damanges due
to incorrect use.

Grp A4 Synthesizer – Owner’s Manual
!
99"
S
VC LOW FREQUENCY OSCILLATOR 1
MIXER
EXT IN - ENV FOLL
CV OUT 0/+8V
CONNECTIONS
CLK IN 0/+5V CLK OUT 0/+5V
LEFT/24db RIGHT/12db
PHONES
GATE IN0/+5VCV IN 1V/Oct
CV OUT 1V/Oct CV IN 24db
AMT
2
56
7
8
9
10
4
3
1
0
0+1
+2
+3
+4
-1
-2
-3
-4
PW
-5 +5
SOURCE CV
VOLTAGE CONTROLLED AMPLIFIER
RELEASEDECAY SUSTAIN
LEVEL
ATTACK
GATE
SEQ
ENVELOPE GENERATOR 2
AM LFO1
OFF
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
STEREO MAIN
MASTER VOLUME
56
7
8
9
10
4
3
2
1
0
GATE AUTO
10
CV VCA
EG2 HOLD
EXT CV
SAMPLE & HOLD - NOISE
RUN/STOP RESET LOOP ON/OFF
GATE OUT 0/+5V
!"#$%&'()*+,-*" ./
0
KYBD
VOLTAGE CONTROLLED FILTER
12 db STATE VARIABLE FILTER24 db LOW PASS FILTER
RESONANCE
56
7
8
9
10
4
3
2
1
0
FREQUENCY
56
7
8
9
10
4
3
2
1
0
ROUTING
24db
12db SER
PAR
DIST/LEVEL
AMT
RESONANCE
56
7
8
9
10
4
3
2
1
0
AMT FM3
AMT
MODE
12db HP
6db BP
NOTCH
12db LP
AMT FM3
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
AMOUNT EG
OVERLOAD
6db
12db
24db
18db
SLOPE
FM2 LFO1
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
ATTACK
GATE AUTO
SUSTAINDECAYHOLD RELEASE
LEVEL
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
AMOUNT EG
56
7
8
9
10
4
3
2
1
0
VELOCITY EG
OVERLOAD
KYBD TRK
REVNOR
SEQ
ON
FREQUENCY
56
7
8
9
10
4
3
2
1
0
10
ENVELOPE GENERATOR 1
NOR REV
REV
NOR
REV
NOR
SEQ
KYBD/S&H
EXT IN
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
PHASEPHASE
FM1 FM1
AUDIO PATH
DIROUT
OFF
DIST/LEVEL
DIST DIST
FM2 LFO1
LOOP
ROW ATRNP
CV IN CLKMOD AUDIOEXT IN
OFF
ROW BROW A ROW A + B
TIME
GATE LOOP
KYBD/S&H
EXT IN
INPUT GAIN
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
FREQUENCY
NOISE
56
7
8
9
10
4
3
2
1
0
RING MOD
VCO2 x VCO3/EXT IN
56
7
8
9
10
4
3
2
1
0
VCO 3 EXT INPUT
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
SUB 2VCO 2
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
VCO 1 SUB 1
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
AUTO PAN
GATE
THRESHOLD
56
7
8
9
10
4
3
2
1
0
INT LFO 1
OFF
WHITE
PINK
INT
LFO 1
OFF
GATE SEQ
MIDI
SYNC
CLOCK
2
56
7
8
9
10
4
3
1
0
GLIDE
2
56
7
8
9
10
4
3
1
0
OFF
GATE
CLOCK EG
AUTO
VCO 1
NOISE
AFT T
S&H
EG 2
LFO 1
VCO 2
LFO 2
VCO 3
SOURCE
MOD W
ENV FOLL
VCO 1
NOISE
AFT T
S&H
EG 2
LFO 1
VCO 2
LFO 2
VCO 3
SOURCE
MOD W
ENV FOLL
CV IN12db
NOR
PHASE
REV
WAVEFORM
ENV FOLL
SHAPING SELECT
EG 1
EG 2
SEQ A+B
AFT T
SEQ A
SEQ B
HOLD
MOD W
S&H
LFO 2
ENV FOLL
LFO 2 SEQ A
MOD W
EG 1
S&HAFT T
KYBD
EG 2
SEQ A+B
SEQ B
LOW FREQUENCY OSCILLATOR 2
VCO PWM VCF 24db/12db
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
56
7
8
9
10
4
3
2
1
0
FREQUENCY WAVEFORM
ENV
FOLL
NGEG 1
EG 2
VCO 1 VCO 2 VCO 3
S&H
EXT IN
SHAPING SELECT
AFT T
MOD W
HOLD
T
TUNING - MIDI
RTRGHOLD
MASTER TUNE
0+1
+2
+3
+4
-1
-2
-3
-4
5
b-5
+#
0+1
+2
+3
+4
-1
-2
-3
-4
TUNE 5
+#
5
b-
OCTAVE
64'
32'
16' 8' 4'
2'
WAVEFORM
0+1
+2
+3
+4
-1
-2
-3
-4
FINE 5
+#
5
b-
VOLTAGE CONTROLLED OSCILLATOR 1
OCTAVE
64'
32'
16' 8' 4'
2'
WAVEFORM
VOLTAGE CONTROLLED OSCILLATOR 2
LFO 1
2
56
7
8
9
10
4
3
1
0
AMT
2
56
7
8
9
10
4
3
1
0
VOLTAGE CONTROLLED OSCILLATOR 3
0+1
+2
+3
+4
-1
-2
-3
-4
TUNE 5
+#
5
b-
OCTAVE
64'
32'
16' 8' 4'
2'
0+1
+2
+3
+4
-1
-2
-3
-4
FINE 5
+#
5
b-AMT
2
56
7
8
9
10
4
3
1
0
LFO 1
2
56
7
8
9
10
4
3
1
0
WAVEFORM
AMT
2
56
7
8
9
10
4
3
1
0
LFO 1
2
56
7
8
9
10
4
3
1
0
SUB -2 SUB -1
LIN
EXP
SYNC VCO1
ON
KYBD
OFF
SUB -2 SUB -1
LIN
EXP
LIN
EXP
RM IN SEL
EXT IN
FM1 SOURCE
VCO 2
NOISE
VCO 3
EG 1
AFT T
LFO 1
LFO 2
S&H
VEL
EG 2
MOD W
PW
2
56
7
8
9
10
4
3
1
0
PWM
2
56
7
8
9
10
4
3
1
0
PWM
2
56
7
8
9
10
4
3
1
0
PW
2
56
7
8
9
10
4
3
1
0
LFO 1 LFO 2
56
7
8
9
10
4
3
2
1
0
PORTAMENTO BEND AMOUNT
56
7
8
9
10
4
3
2
1
0
ON
REV
NOR
SYNC VCO1
ON
PHASE PHASE
REV
NOR
PHASE
VCO1 OFF
KYBD
OFF
MANUALPROGR
EDIT GATE ON
KYBD
OFF
MIDI ACT
VCO 3
REV
NOR
PW
2
56
7
8
9
10
4
3
1
0
PWM
2
56
7
8
9
10
4
3
1
0
LFO1
LFO 2
LFO1
LFO 2
+3
0+1
+2
+4
-1
-2
-3
-4
TUNE 5
+#
5
b-
0+1
+2
+3
+4
-1
-2
-3
-4
FINE 5
+#
5
b-
440Hz
56
7
8
9
10
4
3
2
1
0RANGE
MID
SLOW
FAST
VCA
56
7
8
9
10
4
3
2
1
0
RUN/STOP
SEQUENCER 8 x 2
56
7
8
9
10
4
3
2
1
0
X4
X2
QNT B
OFF
ON
QNT A
OFF
ON
RANGE A
X8
RANGE B
X4
X2 X8
GLIDE A GLIDE B
16X1 8X2
MODE
56
7
8
9
10
4
3
2
1
0
STEP REPEAT
N,N,N+1,N
OFF
X2
X3 X4 N,N+1
N,N+1,N
CLOCK
OFF
RESETSTEP ADV
56
7
8
9
10
4
3
2
1
0
INT
LFO 1 EXT
CLOCK SELECT
A
1 2 3
PWM SEQ ENABLE
A+B
BB
FLT SEQ ENABLE
BB
AA+B
24db 12db
SEQUENCER MODE
FW
BW
FW/BW
PNDL
ALT
RND
TRG
56
7
8
9
10
4
3
2
1
0PW
123
VCO SEQ ENABLECV SEQ CLOCK
HOLD
OFF ON
LOOP
OFF ON
OFF OFF
A B
LEVEL LEVEL
TIME
SEND MODULATION
NOISE
INPUT SOURCE
VCO 2
VCO 1
LFO 1
LFO 2
EXT IN
OVERLOAD
FREQUENCY
56
7
8
9
10
4
3
2
1
0
GATE
CLOCK / TRNP SEQ
B
A
GATE
ON
GATE
ON
END STEP
01
SKIP
NOR
GATE END STEP
ON SKIP
NOR
GATE END STEP
ON
03
SKIP
NOR
GATE END STEP
ON
04
SKIP
NOR
GATE END STEP
ON
05
SKIP
NOR
GATE END STEP
ON
06
SKIP
NOR
GATE END STEP
ON
07
SKIP
NOR
GATE END STEP
ON
08
SKIP
NOR
END STEP
09
SKIP
NOR
GATE END STEP
ON
10
b#
SKIP
NOR
GATE END STEP
ON
11
SKIP
NOR
GATE END STEP
ON
12
SKIP
NOR
GATE END STEP
ON
13
SKIP
NOR
GATE END STEP
ON
14
SKIP
NOR
GATE END STEP
ON
15
SKIP
NOR
GATE END STEP
ON
16
SKIP
NOR
#
00 0 0
0
0
0
0
0
0
bb#
0
02
b#b#b#
0
b#b#
0
b#
0
b#
0
b#b#
0
b#
0
b#b#b#
CLOCK DIVIDER
/3
/2
/1
1/1
/4
1/2T
1/2
/6
/8
1/4T
1/81/4
/12
1/8T
/16
/32
MONO
FM1 SOURCE
VCO 1
NOISE
VCO 3
EG 1
AFT T
LFO 1
LFO 2
S&H
VEL
EG 2
MOD W
FM1 SOURCE
VCO 1
NOISE
VCO 2
EG 1
AFT T
LFO 1
LFO 2
S&H
VEL
EG 2
MOD W
FLT
VCO 3
MAIN
CV INVCA/AFT T
MIDI
GATE OUT 0/+5V
1/16
1/32
ROW A+ BTRNP
MIDI
BA+B
AA

Grp A4 Synthesizer – Owner’s Manual
!
9!"

Grp A4 Synthesizer – Owner’s Manual
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9#"
Grp!A4!!
MAIN!FUNCTIONS!
!
MODULE!TUNING!–!MIDI!
!
This module manages numerous functions related to intonation
of the synthesizer Grp A4, the configuration of MIDI parameters
(through the two-digit display and menu .&+)&), the audio
reference signal generation for tuning.
MASTER!TUNE!CONTROl!
Sets the overall pitch of the synthesizer Grp A4, within a range
of min/max +/-5 semitones.
Due to the analog circuitry of the instrument before adjusting
the tuning it is best to wait about ten minutes with power on,
intil the instrument will reach a stable temperature.
!
VCO!1!PORTAMENTO!ON/OFF!SWITCH!
Allows to release the VCO 1 from the action of .+&3%0,'3+
applied to the voltage of the keyboard; in this way, it is possible
to obtain a different reaction between 82+"9 and the remaining
82+" !:" # (under control Portamento) during the execution of
musical intervals on the keyboard.
VCO!1!BEND!ON/OFF!SWITCH!
With this switch, you can prevent the 82+" 9 from receiving the MIDI Pitch Bend
control and, whe using 82+"9"as Master Hard Sync for 82+"! and #as a slave, mantain
the correct pitch, while the other two slave oscillators will produce interesting
harmonic sweepts under bending.
PORTAMENTO!CONTROL!
Defines the portamento time applied to oscillators under control from analog ports or
MIDI keyboard. You can disable the 82+"9 from portamento with the switch described
above. The portamento time is between a minimum of 0 and a maximum of 3 sec.
Keep in mind that the .+&3%0,'3+ control works only on the Keyboard CV from
the analog 28" (' 1V/Oct, and on MIDI codes Note On from 0(-(" ('. Pitches
programmed in Step 4,>1,'2,& A"B"!"are under control from a pair of independent of
Glide generators, GLIDE GLIDE A and B.
BEND!AMOUNT!CONTROL!
Defines the maximum frequency interval allowed to pitch bend applied to all VCOs or,
with the switch +**" 82+" 9, only on 82+" ! and #. The bend range is between a
minimum of 0 and a maximum of one octave.

Grp A4 Synthesizer – Owner’s Manual
!
9/"
MIDI!ACT(IVITY)!LED!
LED flashes when Grp A4 synthesizer receives MIDI codes on 0(-("('"IJKL.
HOLD!SWITCH!
Permits to artificially prolong the Gate On (if there is enough Sustain Level
programmed in the two Envelope Generators). In this way, with appropriate
programming of the envelopes, it is possible to “freeze” the playing the synthesizer
Grp A4 for producing drones of indefinite duration.
Remember that, in the 82"%0.5(*(,& module, is it possible to put in Hold the amplifier
with the switch 28" 82%; with this control, unlike the previous, musician does not
undertake the two envelope generators (which remains available as modulation
sources), but it keeps always open the amplifier gain in order to simplify filtering for
any external audio signals connected to the ,<3"%1-(+"(' of the synthesizer.
440!Hz!SWITCH!
Triggers the generation of a square wave output at 440 Hz, as a useful reference for
tuning.
RTRG!SWITCH!
Enables or removes multiple trigger from MIDI Note On received at the MIDI IN port
on the rear panel of the synthesizer Grp A4 and used by the two Envelope
Generators. The switch is not active on the gate voltages presented to an analog )%3,"
('"HMNC"8 on the front panel.
EDIT!LED!
Lights when the unit enters .&)&",-(3 mode to access and modify the parameters to
display.
GATE!ON!LED!
Lights up when the instrument receives a MIDI Note On code to the 0(-("(' on the
rear panel or to an analog voltage Gate )%3,"('"HMNC8 on the front panel, or –still- a
Gate extracted from any external signals connected to the gate %1-(+" ,<3,&'%5"
('.13. Obviously, the LED also lights up when the player uses the 0%'1%5" )%3,
button on the front panel.
DISPLAY!
Displays the values associated with the parameters contained in the ,-(3".&+) mode.
MANUAL!BUTTON!
Manually generates the Gate needed for engage the two Envelope Generators; can be
used to play the synthesizer Grp A4 (on a single note…) in the absence of external
controllers and for verify the correct connections between instruments and
amplification.
BOTTONE!PROGR!BUTTON!
Sets the instrument in .&+)&",-(3"OJ=P (see below).

Grp A4 Synthesizer – Owner’s Manual
!
9C"
INCREASE!e!DECREASE!BUTTONS!
For navigating between available display parameters and increase/decrease of their
parameter values.
SUB!MODULE!MIDI!INTERFACE!
It allows access and modification of parameters relating to the operation of the MIDI
interface built into the instrument. With the .&+)&%0 button you’ll see/choose
parameters in rotation (with the first digit of the display) and, with the two switches
('2&,%4, (upward arrow) and -,2&,%4, (arrow down), you select the desired value
(second digit of the display) for the choosen parameter. The condition of EDIT is
displayed via dedicated LED lights.
These parameters are available:
•Program 0. Values Off, 1 ... 1: defines without entering the programming mode the
MIDI receiving channel. This is the only case in which the two digit display
shows the value parameter. In the first position, value = Off, turns off the MIDI
interface. In this condition, the synthesizer can be controlled only by voltage
analog CV/Gate Step or from internal Sequencer.
•Program 1. Values 0 - 1 - 2 - 3 – 4; sets the octave offset value applies on
instrument tuning only when the three oscillators are decoupled from the
control keyboard, with switch Q?7-"+'M+**. The display shows the reading 1.x
(with x equal to the specified value). When the keyboard is reconnected to the
oscillators, the parameter has no value.
•Program 2. Values 0 - 1 - 2 - 3 - 4 - 5; adjusts the octave offset value applied
over the the three oscillators tuning when the MIDI interface is set to OFF. (In
that condition, VCOs are only under control of analog voltages received at the
input on the front panel).
•• Program 3. Values 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9; sets the dividing factor
applied to the 0(-(" position of the 4?'2 selector in module 82" 5+$"
*&,>1,'2?"+42(55%3+&"9.
These are the coefficients corresponding to the nine possible values on the display:
•3.1 = the cycle of the 5*+ lasts 4/4 ie 96 ppq;
•3.2 = the cycle of the 5*+ lasts 2/4 ie 48 ppq;
•3.3 = the cycle of the 5*+ lasts 1/3 of 4/4 bar, ie 32 ppq;
•3.4 = the cycle of the 5*+ lasts 1/4 ie 24 ppq;
•3.5 = the cycle of the 5*+ lasts a 1/4 triplet, ie 16 ppq;
•3.6 = the cycle of the 5*+ lasts 1/8 ie 12 ppq;
•3.7 = the cycle of the 5*+ lasts a 1/8 triplet, ie 8 ppq
•3.8 = the cycle of the 5*+ lasts 1/16 ie 6 ppq;
•3.9 = the cycle of the 5*+ lasts 1/32 ie 23 ppq.
These coefficients are identical to those used in the Step Sequencer on the Clock
Divider switch for positions lebeled RS"RSTPKUP.

Grp A4 Synthesizer – Owner’s Manual
!
9D"
!
!
!
VOLTAGE!CONTROLLED!OSCILLATOR!1,!2,!&!3!MODULE!
!
The three analog oscillators are the main source of the sound synthesizer Grp A4;
their structure is almost identical, with small differences in the choice of modulation
sources and functions. Each oscillator can choose from six different waveforms (with
variable symmetry on square wave), can adjust the frequency in octaves, semitones and
cents tone, has two busses dedicated to the modulation frequency (one switchable in
Linear and Exponential FM, equipped with a reverse phase selectable). In addition, the
first two 82+ have a square wave suboscillator circuit at one or two octaves below;
the 82+"! and #may be placed in Hard Sync under control from 82+"9. All 82+s can
be individually detached from keyboard voltage (CV analog or MIDI notes) and left at
complete disposal of Step 4,>1,'2,&"A"B"! (it is possible, however, to transpose the
sequence using the analog connections &+$" %M%N7" 3&'.). Finally, in the adjacent
module 31'(')"V"0(-(, you can disable the receipt of Portamento (switch +**"82+9"
.+&3%0,'3+) and Pitch Bend (switch +**"82+"7,'-"9) to differentiate between the
harmonic oscillators under Hard Sync Master / Slave and their behavior frequency.
In addition, the frequency of the oscillators can be placed individually under control of
the rows A, B, A + B of Step 4,>1,'2,&" A" B" !, acting on the switches 82+" 4,>"
,'%75,.
OCTAVE!(VCO!1,!2!e!3)!SELECTOR!
Used to set the pitch of the oscillator on the desired octave values; available range
from a minimum of 64 'and a maximum of 2'.

Grp A4 Synthesizer – Owner’s Manual
!
9E"
TUNE!CONTROL!(VCO!1,!2!e!3)!!
Defines the coarse deviation of pitch (against the nominal value for the entire
instrument previously set with the 0%43,&"31',"31'(') inside the module 31'(')"-
MIDI); parameter range is +/- 1 octave.
FINE!CONTROL!(VCO!1,!2!e!3)!!
Defines the fine deviation of pitch (against the nominal value for the entire instrument
previously set with the 0%43,&" 31'," 31'(') inside the module 31'(')" - MIDI);
parameter range is +/- 1 tone.
WAVEFORM!CONTROL!(VCO!1,!2!e!3)!
Allows selection of the six available analog waveforms in the synthesizer Grp A4. The
selection includes:
•Sine wave, composed of sole energy on fundamental harmonic, it is important to
achieving pure tonal timbre, not very flashy, but suitable for reinforcing other
waves.
•Triangular wave; composed of only odd harmonics, alternately in phase and in
antiphase, with exponential energy decay. It is suitable for making soft sounds,
with a strong presence on the fundamental and a minimum opening on trebles.
•Triangular + Sawtooth wave; is the sum of triangular and sawtooth, and is based
on greater energy over the fundamental and good opening on odd and even
harmonics.
•Sawtooth wave; composed of odd and even harmonics, with linear energy decay
and alternately in phase and antiphase; is equipped with a are rich, full bodied
sound particularly suitable for the realization of brass, strings and “synth”
tones.
•Square + sawtooth wave; is the sum of the two waves and offers a significant
reinforcement portion of the odd harmonics (from square wave). The square
wave content is adjustable in symmetry with the .$ command.
•Square wave; composed of only odd harmonics, alternately in phase and in
antiphase with linear energy decay. It is suitable for the production of woody
timbre, very different and complementary to those typical sawtooth wave. Its
symmetry can be varied with the command .$, with a strong variation the
harmonic content.
PW!CONTROL!(VCO!1,!2!e!3)!
Allows you to adjust the symmetry of the square wave generated in the oscillator, to
reach all possible variations of wave and rectangular pulse. The harmonic content of
the waveform will vary in a manner connected to the relation of symmetry with the
control set: in the resulting sound, all of the harmonics whose number is a multiple of
the ratio obtained will be missing; in this way, a rectangular wave to 30% will contain
only harmonics 1, 2, 4, 5, 7, 8, 10, 11, 13, 14 ...
PWM!CONTROL!(VCO!1,!2!e!3)!
It sets the amount of the modulating signal received into the oscillator for automate
the symmetry variation of Pulse Width. The Pulse Width Modulation, when entrusted
to a cyclical source control, produces a regular sequence of narrowing and widening
symmetry, giving the resulting audio signal a characteristic timbre that recalls - even

Grp A4 Synthesizer – Owner’s Manual
!
9A"
with a single sound source - the presence of multiple oscillators not perfectly
frequency matched to each other.
LFO!1/LFO!2!SWITCH!(VCO!1,!2!e!3)!
It allows the choice between two modulation sources provided for the Pulse Width
Modulation. Although, apparently, the availability seems limited to 82"5+$"*&,>1,'2?"
+42(55%3+&"9 and 5+$"*&,>1,'2?"+42(55%3+&"!, you can use for the pulse width
control all sources connected at the $%8,*+&0 selector in 5*+"!, thus ensuring access
at PWM for transient signals coming from different parts of the synthesizer Grp A4 or
from external world.
In addition to the sources listed, you can directly use the values programmed in Row
A, B and A+B of Step 4,>1,'2,&"A"B"! using the three switches .$0",'%75,"4,>.
FM!1!SOURCE!SELECTOR!(VCO!1,!2!e!3)!
For choose the source applied to the first buss for the frequency modulation. The
eleven possible sources available on each selector varies slightly from oscillator to
oscillator. Here is a list of all the sources available:
•5*+"9"W82+"9:"!"XS="#Y; signal from 82"5+$"*&,>1,'2?"+42(55%3+&"9 choosed
after its $%8,*+&0"UPZP[LJK."
•5*+"!"W82+"9:"!"XS="#Y; one of the signals on $%8,*+&0"UPZP[LJK in the 5+$"
*&,>1,'2?"+42(55%3+&"!"OJ=\ZP. Keep in mind that with this selector, you
can use either triangle and square wave, or audio signals from 82+" 9:" !:" # e
Noise White/Pink and, still, the transient controls from ,)"9:"!"P"4;@, and still
,<3"(' signal. All these sources can be used proficiently for driving the 82+s
frequencies. "
•82+"9"W82+"!"XS="#Y; the audio signal from 82+"9 for driving 82+"!"XS="#. "
•82+"!"W82+"9"XS="#Y; the audio signal from 82+"! for driving 82+"9"XS="#."
•82+"#"W82+"9"XS="!Y; the audio signal from 82+"# for driving 82+"9"XS="#."
•'+(4," W82+" 9:" !" XS=" #Y; is the aperiodic audio signal from Noise Generator,
after the switch .('QM$@(3, into the module 4%0.5,";"@+5-"6"'+(4,."
•4;@"W82+"9:"!"XS="#Y; signal from module 4%0.5,";"@+5-"6"'+(4,."
•,)"9"W82+"9:"!"XS="#Y; the envelope curve from ,'8,5+.,"),',&%3+&"9 sub
module, located into 8+53%),"2+'3&+55,-"*(53,&. "
•,)"!"W82+"9:"!"XS="#Y; the envelope curve from ,'8,5+.,"),',&%3+&"!"U\]"
OJ=\ZP, located into 82"%0.5(*(,&."
•%*3"3"W82+"9:"!"XS="#Y; the Channel Aftertouch control received at 0(-("('."
•0+-"$"W82+"9:"!"XS="#Y; the Modulation Wheel control received at 0(-("('."
•8,5"W82+"9:"!"XS="#Y; the Key Velocity value read at 0(-("('."
"

Grp A4 Synthesizer – Owner’s Manual
!
9G"
"
FM!1!AMT!CONTROL!(VCO!1,!2!e!3)!!
-P^RSPU" L_P" XOJ\SL" J^" L_P" OJ=\ZXLRS`" UR`SXZ:" [_JJUP=" aRL_" L_P" UPZP[LJK" =PU[KR]P="
X]JTP:"XS="XIIZRP="LJ"L_P"[JSLKJZ"J^"L_P"JU[RZZXLJK"^KPb\PS[cd"
"
FM!1!EXP/LIN!SWITCH!(VCO!1,!2!e!3)!!
%ZZJaU" cJ\" LJ" [_JJUP" L_P" ZRSPXK" JK" PBIJSPSLRXZ" OJ=\ZXLRJS" XIIZRP=" XL" L_P" JU[RZZXLJK"
^KPb\PS[cd"(^"L_P"JU[RZZXLJK"RU"\S=PK"ZRSPXK"*0"^KJO"XSJL_PK"JU[RZZXLJK"XL"X\=RJ"KXLP:"RL"
aRZZ" ]P" IJUUR]ZP" LJ" [_XS`P" L_P" _XKOJSR[" [JSLPSL" L_P" JU[RZZXLJK" aRL_J\L" ZJURS`" L_P"
OPZJ=R["b\XZRLcd"$RL_"PBIJSPSLRXZ"*0"XL"X\=RJ"KXLP:"cJ\eZZ"ZJJUP"L_P"SJORSXZ"IRL[_:"]\L"
RL"aRZZ"PXURPK"LJ"`PL"]P_XTRJKU"_XKOJSR[XZZc"^XRKZc"[JOIZPBd"
"
FM!1!PHASE!REV/NOR!SWITCH!(VCO!1,!2!e!3)!
Allows the phase inversion for the modulating signal choosed with the selector switch
SOURCE FM 1 and applied to the oscillator frequency.
FM!2!LFO!1!CONTROL(VCO!1,!2!e!3)!
Chooses the amount of signal received by the module 82" 5+$" *&,>1,'2?"
+42(55%3+&"9 and applied, on the dedicated bus, at the modulation frequency of the
oscillator.
KYBD/OFF!SWITCH!(VCO!1,!2!e!3)!
Allows you to detach the Keyboard Control Voltage (both in its analog format, the
received at input connection IN 1V/Oct CV, and in its digital form, received at the
0(-("(' port) from the frequency control of the oscillator. If the switch is off, you’ll
can control the pitch of the oscillator only through the programmed values in Step
4,>1,'2,&"A"B"!d"
On the oscillator with the OFF Keyboard, you can still apply a pitch offset with the
software menu options available into .&+)& menu on the display (in the module
31'(')"V"0(-().
"
SUB!1/SUB!2!SWITCH!(VCO!1!e!2)!
Allows you to choose the square wave sub oscillation produced at lowest octaves by
frequency dividing the audio signal; the sub oscillator frequency will be equal to -1
octave (417"9) or -2 octaves (417"!). The level of the sub oscillator signals can be
adjusted individually in the 0(<,& module (see below).
SYNC!VCO!1!SWITCH!(VCO!2!e!3)!
Puts individually the 82+"! and #under Hard Sync control from 82+"9, which acts as
the Master. Remember that, in the 31'(')"V"0(-( module, you can detach 82+"9 from
receiving the Pitch Bend and Portamento, allowing interesting differences in behavior
between VCO 1 (Master) and VCO 2, 3 (Slave) under external modulation.
"
RM!IN!SEL!SWITCH!(VCO!3)!
Although it is housed into the 8+53%)," 2+'3&+55,-" +42(55%3+&" # module, this
switch is about the the Ring Modulator circuit. It makes possible to choose whether,
within the Ring Mod, the signal produced by the VCO 2 will be processed along with
that generated by the 8+53%),"2+'3&+55,-"+42(55%3+&"# (switch in position 82+"#)

Grp A4 Synthesizer – Owner’s Manual
!
!H"
or the external one, coming from other equipments connected to the port ('"%1-(+"
,<3 (switch to ,<3"(')."