Alto MINI-TUBE Service Manual
Service Manual
Model: MINI-TUBE
NONO TUBE PREAMP
www.altoproaudio.com
Version: 1.1
CONTENTS
1. Specification ――――――――――― 1
2. Block Diagram ――――――――――― 1
3. Schematic Diagram ――――――――――― 3
4. Printed Circuit Board ――――――――――― 3
5. Wiring Diagram ――――――――――― 1
6. Test Procedure ――――――――――― 0
7. Electrical Parts List ――――――――――― 10
8. Exploded Views & Mechanical Parts List ――― 2
9. Troubleshooting ――――――――――― 0
10. Notes ――――――――――― 0
MINI-TUBE TECHNICIAL SPECIFICATIONS：
1. Specification
Preamp Bandwidth： 20Hz~50KHz/±2dB
Number of Channels：One
Performance：
THD+Noise：0.05% @ GAIN +0dBu (A-Weighting)
OUTPUT LEVEL(MAX)：+22dBu
Noise Floor：-88dBu(±2 dBu)
Signal to Noise：>108dBu
Input：
Connectors：XLR and 1/4”
Input Impedance, XLR：1.3K Ohms
Input Impedance, High Z 1/4： 1Meg Ohms
Output：
Output Impedance, XLR Balanced： 51Ohms
Output Impedance, High Z 1/4”TRS Unbalanced：51Ohms
Panel Controls：
Tube Drive：0dB~+40dB
Gain：0dB~+30dB
Phase Reversal
-20dB Pad
+48V Phantom Power
Metering：
VU Meter：-20dBu~+5dBu
Clip LED：+20dBu
Power Supply：
Input：18VAC/1000mA
Power：12 WATT
Physical：
Weight：0.7Kg
Size： 1U Rack
Dimension：W*D*H 210*93*44
D
2.Black Diagram
6
C
213
4
B
OUTPUT
213
4
A
54321
M
A
VU
LOW-CUT
+20dB
R
DRIVE +40dB
G
+20dB
A
I
D
TUBE-12AX7
K
GAIN +20dB
A
O
L
B
PHASE PAD(20dB)
213
4
MICROPHONE INPUT
D
C
213
4
1 2 3 4 56
B
A
+15V
3. Schematic Diagram
FUSE
LOW-CUT
+48V+15V
+15V +15V
TR2
1A
PJ3
CLIP
OUT+
IC6C
IC5C
IC4C
IC3C
IC2C
IC1C
7815
AC18V
OUT-
4580
4580
4580
4580
4580
4580
C22
D12
104P
1N4004
A
CON7
CN4
7
6
5
4
3
2
1
6
5
4
3
2
1
TO FP-BOARD TO FP-BOARD
CN3
CON6
LED6
LED
LED7
LED
4 8
-15V
4 8
4 8
4 8
4 8
4 8
R47
C46
47u/25V
C45
1000u/25V
C43
100u/100V
TP2
A
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R49
1K 1/2W
R50
1K1/2W
-15V -15V
+15V
C35
104P
C34
104P
C33
104P
C32
104P
C31
104P
C30
104P
C29
104P
C28
104P
C27
104P
C26
104P
C24
104P
C25
104P
0R
C23
104P
-15V
C47
47u/25V
TR3
7915
C44
1000u/25V
D11
1N4004
1 2 3 4 5 6 78
GND
B
IN
OUT
CON8
CN5
8
7
1
2
R48
+15V
TO VU-METER
VU
IN-
IN+
123
CN7
CON3
6
20R
5
4
3
+48V
2
1
R51
0R
TUBE-BOARD
-15V
CUT-OUT
PHOTOM
FROM CN8
IN-
IN+
CN-BAL-MALE
213
4
C49
104P
C48
104P
R46
49K9
R45
49K9
C38
47u/50V NP
R17
51R1
C14
CLIP
7IC6B
33P
R43
10K
4580
5
6
R42
10K
VU
R32
12K
C15
104P
C53
D5
5D
4580
6
10u/25V
C4
47P
R12
1K15
R11
1K
D8
1N4004
TR1
LM317
D6
1N4004
C10
47u/63V
+48V
C21
104P
D9
IN4004
R40
2
OUT
ADJ
IN
3
270R
C9
1
47u/63V
R39
10K
C42
100u/100V
D10
1N4004
1N4004
C41
100u/100V
1 2
D7
7IC5B
5
CN9
R6
820P
CON3
1K5
C
CN6
CON2
CN2
PJ2
PHONEJACK3
213
4
R18
51R1
R44
49K9
C37
47u/50V NP
R16
51R1
FROM CN10
47P
C17
123
CN10
CON3
213
4
LOW-CUT
CUT-OUT
TO CN9
PJ1
PHONEJACK3
2
C36
47u/50V NP
R15
51R1
1IC6A
R33
4K99
C13
33P
4580
3
2
R41
10K
1IC5A
4580
3
R38
20K
104P
C11
D
8
R28
100R
R20
1M
VR2B
C1K
R35
301K
7654321
R19
1M
PHOTOM
R7
162R
C1
100u/63V
R3
6K81
R4
6K81
213
4
CN1
CN-BAL-FEMALE
1IC4A
C6
1.0u
4580
3
2
R26
100R
VR2A
C1K
R34
301K
1IC3A
1.0u
C5
4580
3
2
VR1
A10K
R14
51R1
D1
H2Y
123
CN8
CON3
7
150P
C40
R30
100R
IC4B
4580
5
6
R27
100R
R37
301R
R24
1M
C19
56P
7IC3B
C39
150P
4580
R29
100R
5
6
R25
100R
R36
301R
R23
1M00
C20
104P
R22
1M
C18
56P
IN OUT
7IC2B
47P
C3
4580
R21
1M
5
6
C12
C52
R10
C2
47P
R13
3K16
R8
1K
3
D2
H2Y
R5
1K5
C7
47u/63V
OUT+
104P
47u/25V
1K
SGAND
3
1IC1A
4580
2
R1
10R
C50
820P
R52
0R
3
2
1
1IC2A
3K16
R31
4580
2
R9
1K
7IC1B
4580
5
6
D3
332P
H2YD4H2Y
R2
10R
C8
47u/63V
C51
OUT-
C16
TO CN7
D
C
B
D
C
B
A
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-15V
LED1
PHASE
LED2
PAD
LED3
PHOTOM
LED4
LOW- CUT
Date:
C1
680P
123
SW1:1
IN+
R1
1K8
456
SW2:2
456
SW1:2
R2
1K8
123
PHASE
SW2:1
R7
619R
PAD
R8
169R
P
PAD
SW2:4
P
PHASE
IN-
OUT+
C2
123
101112
PAD
101112
SW1:4
R3
1K8
680P
SW3:1
PHOTOM
R9
619R
P
P
PHASE
OUT-
C3
680P
123
R4
1K8
SW4:1
LOW- CUT
456
456
LOW- CUT
C4
680P
+15V
+48V
PHOTOM
P
SW3:2
PHOTOM
P
SW4:2
LOW- CUT
CUT-OUT
CLIP
LED5
CLIP
R5
1K
R6
1K
PHOTOM
CUT-OUT
LOW- CUT
7
6
5
4
+48V+15V
3
2
1
CN4
CON7
6
5
-15V
4
3
2
1
CN3
CON6
IN-
IN+
OUT-
OUT+ CLIP
1 2 3 4 56
D
C
B
A
D
4
C
B
A
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321
PT1
6
HT1
5
4
HT2
R2
10K
GT1
7
3
KT2
R1
10K
1234567
CN5
KT1
GT2
+48V
8
HM
9
TB1
TUBE-12AX7
TB1
1
2
PT2
OUT
IN
8
CON8
1 2 34
D
C
B
A
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