Owner’s Manual

Manuel d’utilisation

Bedienungsanleitung

Manual de Usuario

2S JGFE

AD30VT modification for FX insert and return

signal

Even though the AD30VT is a great tone little amp, it lacks a simple feature that it doesn´t necessarily adds a lot of production cost to Vox. And this feature is very useful for all guitar players: the effects in and out jacks for external signal processing.

I asked myself if this could be simply added. And having the Service Manual, where there are the schematics and block diagrams, I started analyzing where this mod could be done. So I called my father who is an electronic engineer, analyzed the schematic, and spotted the place where we would bypass the signal. That is near the LINE OUT jack. So the ob-jective was to get a LINE OUT signal without cutting the speaker output and without mess-ing with the LINE OUT jack itself.

As you can see in this schematic, the LINE OUT signal comes after the MASTER VOL-UME, passes through resistors and capacitors to level de signal and goes straight to the jack. As this jack is a switching one (it cuts when a plug is inserted), we needed to make the bypass just before the jack pins. We need two bypasses, one for the signal going out ( that would be the TO FX UNIT) and one for the signal going in to the Valve Reactor circuit ( FROM FX UNIT).

As you can see, the LINE OUT signal is split in two for stereo reasons. We only need to cut on one point of the split signal, where the green arrow is pointing. The other point is where the return signal goes directly to the VR circuit, the red arrow. So we need to break the circuit in these two points.

After breaking the circuit, we will have four points, A, B, C, D, as you can see in the follow-ing figure. In this figure I added the two new mono jacks so you can understand the mod-ded signal flow. The wires make the connections to the jacks.

1 2 3 4 5 6 7 8

A

B

C

D

87654321

D

C

B

A

Q1KTC3198GR

Q2KTC3198GR

SP18ohm

C1100uF/35V

C3247uF/25V

C9

1uF/50V

C11

NU

+15V

C350.22uF

C2622uF/35V

C2722uF/35V

C29

220uF/35V

C30

220uF/35V

+Vcc(+30V)

-Vss(-30V)

C43

10uF/25V

+15V

C42

10uF/25V-15V

C16

0.1uF

C17

0.1uF

Q3KTC3198

A/AB

C31

10uF/16V

C8

1uF/50V

C10

1uF/50V

Max

Max

Min

Min

2

3 4 51

BK

BG

BP

9B

H

AH

CH

V1A12AX7

7

8

6

AG

AP

AK V1B

12AX7

-15V

-15V

-15V

-15V

-15V

+15V

Q4KTA1266

12

3

4

8

IC2ANJM2082D

5

67

IC2BNJM2082D

12

3

4

8

IC3ANJM2082D

5

67

IC3BNJM2082D

R14

2.2k

+3VD

R9

22k

R4047k

-15V

+3VD

R2210k

R10

10k

C410.01uF

PHONE / LINE OUT123456

J2

PHONE_JACK_SW

C120.001uF

C1347pF

R19

470k

R30

68k

R21k

C30.1uF

KLM-2464 1.61

VOX

AGNDDGND

J1

PHONE_JACK STEREO

FOOT SW

R6910k

C500.1uF

HEATER1HEATER2

2004.2.6

9

10 11

IN3

D3 S3

IC1CDG211

IN1

D1 S1

1

2 3

IC1ADG211

16

15 14

IN2

D2 S2

IC1BDG211

8

76

IN4

D4S4

IC1DDG211

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

CN1

EH-9

RES_FRQ

POWER LEVEL

0 : ON1 : OFF

0 : ON1 : OFF

0 : ON1 : OFF

0 : ON1 : OFF

V+

V-

GND

13

5

4

12

DG211

IC1

C150.1uF

C14

0.1uF

R722k

-15V

+15V

C60.1uF

C50.1uF

11

22

CN2

VH-210 INCH

R11k

R54.7k

R64.7k

R38

47k

R3

4.7k

R3933k R4

4.7k

R20

220

R23

47k R2433k

R27

47k R2833k

R26

2.2k R810k

R41330

R425.6k

R32

330k

R31

330k

R33

330k

R34

330k

R35

3.3k

R36

3.3k

R434.7k

R15

2.2k

R18

2.2k

R17

2.2k

R48

0.47(3W)

R4610 (1W)

+3VD

3

2

1

VR1A100kB

3

2

1

VR1B100kB

R21

220

R2510k

R441.8k

R452.2k

R29 22k

+

C34 NU

+ C3347uF/35V

Title

Size Number Revision

Date Sheet of2/2

A2

AD30VT POWER PCB

+3VD

3

1

2D1KBP206G

3

4

5

C36

2200uF/50V

C37

2200uF/50V

C180.1uF

C190.1uF

1 3

2

V V

GNDIN OUT

IC57815

C200.1uF

C210.1uF

C220.1uF

C230.1uF

D21N4002

D51N4002

C38100uF/25V

C39100uF/25V

4

D7SHSW04M

6

7

C452200uF/16V

1 3

2

V V

GNDIN OUT

IC7BA033T

C240.1uF

C250.1uF

D61N4002

C40100uF/6.3V

5

8

9

HEATER1

HEATER2

1

10

2

R49

330(1W)

R50

330(1W)

R51

100(1W)

R52

100(1W)

1 2

SW1SW-SPST

F1

FUSE

F2

FUSE

1

OUT 3IN2GND

IC67915

R54470

LED1RED(5mm)

11

22

33

CN4

EH-3

1 1

2 2

3 3

CN5

EH-3

POWER

POWER 11

22

33

44

55

66

77

88

CN3

EH-8

R47 10 (1W)

C44 0.22uF

D4 1N4002

D3 1N4002

Chassis GND Circuit GND

Chassis GND

NC FOOT_ SW_R

+VCC(+30V)

-VSS(-30V)-15V

+15V

+3VD

R55

0

AGND

DGND

NC : No Connect

D141N4148

D151N4148

D81N4148

D91N4148

FB1

FB-M C4622pF

LINE OUT

PRE OUT

PHONE_DT

PHONE_DT

LINE OUT

PRE OUT

FOOT_SW_LFOOT_SW_L

PHONE_DT

LINE OUT

PRE OUT

LINE OUT

PRE OUT

PHONE_DT

FOOT_ SW_R

R5610k

HEATER1

HEATER2

HEATER1HEATER2

From MAIN PCB

To MAIN PCB

Q5KTC2874

R57

1k

C47 NU

R58470

R591k

POWER SUPPLY BLOCK

POWER BLOCK

C48100uF/25V

R6147(1W)

Q7KTA1266

Q6KTC3198

R6010k

+3VD

R37100k

R5310k

D121N4002

D131N4002

C490.22uF/50V

Q8

KTC3198

R64

22k R6222k

R65

10k

+3VD

Q9KTC3198

R632.2k

R6716k

0 : A1 : AB

VL

+3VD

R7047k

C53

47uF/35V

-15V

+15V

C2810uF/35V

R66220k

R683.3k

ADJUSTMENT RESISTOR

R1110k

C70.1uF

+3VD

D101N4148

D111N4148

FOOT_SW_L FOOT_SW_L

FOOT_SW_RFOOT_SW_R

FB2

FB-M C5522pF

C54100uF/25V

R7347(1W)

-15V

C24.7uF/50V

C410uF/16V

C56

10uF/16V

3

14

10

9

7

8

IC4 LM3886

R1222k

C630.1uF ceramic

C640.1uF ceramic

Shassis GND

Shassis GND

C570.1uF

C580.1uF

C590.1uF

C600.1uF

C610.1uF

C620.1uF

Shassis GND

Shassis GND

Shassis GND

Shassis GND

ceramic ceramic ceramic ceramic

ceramic ceramic

ceramic

ceramic

ceramic

ceramicceramic

ceramic

ceramic ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

ceramic

C65NU

C51

3pF ceramic

NU : No Use

R16

0

R130

1,5

C520.1uF

C6610pF

ceramic

ceramic

C67

3.3uF/50V

C68

3.3uF/50V

Vishay Siliconix

R71 47k_F(1%)

R72

47k_F(1%)

(Delete=6dB up)

If the output power is not high enough, please delete both R67 and R68.

Even doing above modify, if the output power is not go to correct level, please exchange the TUBE itself.

Case 1: nothing is plugged

The signal goes to point A, then to point JA. As no plug is inserted, the jack is closing the circuit, so the signal passes to point JB, returns to point B, passes through point C, then jumps to JC, goes to point JD and returns to point D, which then goes to VR circuit.

Case 2: we connect the IN and OUT jacks for FX unit

The signal goes to point A, then to point JA. Now we are breaking the circuit, so the signal goes out TO FX unit input and no signal is getting to point JB and B. So, we are getting a return signal FROM FX unit output into point JD (avoiding the signal to JC and C) and from JD to point D which goes to VR circuit with the processed signal. Got that? Easy...

Case 3: we plug LINE OUT or a headphone only

Similar to case 1, but the the LINE OUT is breaking the VR circuit, so we get a signal from point B (JA and JB are closing the circuit) and other part of the stereo signal.

Case 4: we plug the FROM FX unit jack

In this case we are getting the signal directly from de fx unit, so we can bypass the AD30VT preamp section and feed the VR directly.

So, to end the theory, four possible scenarios are taken into account with just breaking the circuit at two points.

MATERIALS NEEDED

Ok, all we need is the following:

• 2 mono 1/4 phone switch jacks

• 4 shielded cables (I got them from old headphones)

• Cutter

• Tin

• Solder iron. Drill.

• A bench or desk with good lighting

PROCEDURE

Note 1: If you are unsure of this, just don´t do it! If you know someone with a background in electronic/electric engineer or technician, ask him if he can do it for you. If you feel sure about this, let´s go on with the steps!

Note 2: Obviously, I am not responsible for whatever happens to you and your amp. Take this procedure at your own risk.

1. Unplug all cables and unscrew all screws. First the ones on the back then the ones on the sides.

2. Remove the back panel and unplug the speaker cables. Remember or mark their insert positions.

3. Remove the amp chassis.

4. Remove screws from the bottom of the chassis. There are four plated ones and two black ones (that hold the black heat sink).

5. Remove the nuts from the LINE OUT and FOOT SW jacks. Remove de AMP LEVEL knob and nut.

6. Cut the plastic tie that holds the transformer colored wires with a bunch of white wires that go into the main PCB.

7. Carefully pull out the PCB while holding the heat sink in place (because it is screwed to the LM3886 amp chip) and turn it so that you can see the green side of the PCB. Be-careful with the tube not to touch the top PCB.

8. Locate the LINE OUT jack pins. See photo:

9. With a sharp cutter, cut between the labeled points A-B and C-D. In the photo these are marked in blue. You need to cut enough to break the PCB copper path.

A

BCUT

G

CUT

DG

C

10.Once cut, test connectivity with a tester, between points A-B and C-D to see if you did a good cut.

11.Get four shielded cables. I used them from a headphone cable and got one cable with a red wire plus the shield and a black wire with the shield. So you will end having one pair red/shield and one pair black/shield (or whatever other color). Twist the ends of the wires and “paint” them with tin with a well heated solder iron.

12.Solder the red wires to the tip of each of the mono phone jacks. These are points JA and JD in the schematic. Solder the shields to the ground tip. Next, solder the black wires to the switch of each of the mono phone jacks. These are the points JB and JC.

13.Ok, get one of the jacks and label it TO FX. Then solder the red wire end to pin A (it is easier to use the adjacent upper pin on that same copper path) on the PCB. Then sol-der the shield wire to point G (ground). Next, solder the black wire to pin B and the shield wire to point G.Get the other jack and label it FROM FX. Then solder the red wire end to pin D on the PCB. Then solder the shield wire to point G (above D). Next, solder the black wire to pin C and the shield wire to point G. See photo:

14.Test connectivity with a tester between point A-B and C-D. As the circuit is closed, there should be connectivity.

15.Plug in guitar cables to both TO FX and FROM FX jacks to see it there is connectivity. When we plug we are bypassing so there shouldn´t be connectivity.

16. If everything is OK, you can run a real test to see if it works. Just put the PCB back into the chassis. Only screw the heat sink. Put the chassis in the box but the other way round. Plug speaker cables and power cord. Turn on the amp and see if it is OK. If there is no fire is because everything is OK!! Plug your FX unit to the TO FX jack and FROM FX jack on the amp. Now the signal should be going to your FX unit without cut-ting the speaker! Test it!

17. If everything is OK, unplug everything and pull out the chassis again. Screw the plated screws back to the chassis again.

18.Now you need to drill 2 holes on the chassis for the new jacks. See photo! Make them apart enough so the jacks don´t overlap ( I wasn´t careful enough! I recommend drilling both on the vertical line of the LINE OUT jack). Blow away any metal and plastic parti-cles after you drill de holes. Mount the jacks.

Red Wire

Black WireShield Wire

Red Wire

Black Wire

Shield Wire

19. Now you can mount the rest of the nuts and knob from the rear panel. Insert the chas-sis again in the box. Connect the speaker cables. Position first the back lid. Then screw everything and close the box.

20.GOOD JOB SHAGGY!

If everything went OK and I didn´t make mistakes on the steps described, you would now have an AD30VT with an FX send and return. So you can have the amp´s FXs plus your external FXs unit. Pretty cool! This was a cheap and quick solution. My testings so far yielded good results. Have FUN!

The Ech

See other pictures after pulling out the chassis: