AD 797 Mic preamplifier DIY kit
Warning
This document is distributed for educational purposes only. This equipment operates at potentially lethal voltages. Only trained, qualified personnel should operate, maintain, or
service it.
www.diy-tubes.com
The kit includes: PCB OU AD797ANZ (dip8) Resistors Film Capacitors Multilayer Ceramic Capacitors Tantalum capacitors Gain potentiometer (C5k) Connectors As a bonus - stands for a PCB
Installation of components on the board starts with resistors and jumpers.
Solder a pair of matched resistors 6k8 (R1, R2)
The following jumper is connecting points A and B on the circuit board.
Two resistor 2k (R3, R4). The kit includes a matched pair.
Solder two resistors 33R (R5, R6)
And two resistors 3k (R8, R10)
Resistors 100R (R7, R9)
Move on to installation of sockets for ICs. Pay attention to how the sockets are oriented on the board.
One side of the sockets has a notch that indicates the direction in which the chip has the "key". See the picture.
Note - the resistor R26 (10k) is not included in the kit and is designed for the version with the rotary switch gain control. Since we have an option with potentiometer - this resistor we do not solder.
We now move on to a couple of 220p film capacitors in the feedback op-amp circuit - C5 and C6. Please note: The kit includes another two 220p capacitors (multilayer ceramic), do not confuse their place of soldering.
Optionally, you can use the connector for phantom power switch connection (toggle switch is not included in the kit).
Solder two 22p capacitors (C3, C4).
Next, install 4pcs 100n (0.1u) capacitors: C9, C10, C15, C16.
Next solder tantalum capacitor. Please note the capacitors are oriented on the board. Positive pole is indicated on the body and has corresponding sign. It is important not to reverse the polarity, be careful. Forming capacitor leads.
Now solder 220p ceramic capacitors (C3, C4)
And the capacitor in the phantom power circuit 100n (0.1u) - C28 (not indicated in the circuit).
Prepare connectors. Combine connector - groove and comb let us get a single 5-pin block.
Similarly, we obtain a block of 4 pins.
Mount on the board.
The remaining three-pin connector is for power supply use.
Mount two polypropylene 2u2 capacitors (C1, C2). The board allows to use capacitors with lead spacing of 7.5 mm to 15 mm.
Insert the ICs. Pay attention to how the ICs oriented on the board, the location of a "key". Optionally, before installing the ICs you can test the correct installation of the elements on the PCB, bring to the board power supply (+15 V,-15V), and measure the voltage at the terminals 7 and 4 of the sockets. After that, insert the chip.
Installation of the main board is finished. It remains to instal the gain pot.
The gain control can be organized in two ways - using the potentiometer (the most simple and cost-effective) and rotary switch (more difficult for beginners, and therefore not used in the kit). For installation we use a C5k potentiometer and a 10R resistor.
Soldered jumper between the center tap and the left tap of the potentiometer.
Bind a resistor at the right tap of the potentiometer.
Solder.
Solder the wire in similar manner.
Solder the second wire to the left tap of the potentiometer.
Isolate resistor with heat-shrinkable tubing.
After we finished the installation, it is necessary to connect the power (to power the circuit requires power supply wich provides DC voltage +15v –15v), connect gain pot and input and output XLR. After assembly, adjustment scheme is not required. Note that the scheme is fully balanced. Verify the source and the signal receiver are connected with a symmetrical line. Typical wiring diagrams are shown in the diagrams below.
AD797N
+
-
+VS
-VS OFF
OFF
CO
MP
AD797N
+
-
+VS
-VS OFF
OFF
CO
MP
6k81
6k81
2k2k
33R
33R
100R
3k
100R
3k
2u2
2u2
220p
220p
220p
220p
22p
22p
0.1u
0.1u
4u7
4u7
4u7
4u7
0.1u
0.1u
GND
GND
10R
C5k
+VS, -VS of AD797 are on pin 7 and 4 (+18v, -18v)
Note:
AD797Mic preamplifier
(Potentiometer gain)
Solder R24 (10R) on the Gain potentiometer lug (see interconnections)
XLR pin 1 goes to ground (chassis)
IC13
26
47
158
IC23
26
47
158
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
C1
C2
C3
C4C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
R24
GA
IN
12
3
+48v
XLR pin3
XLR pin2
XLR pin1 XLR pin1
XLR pin2
XLR pin3
++
++
A
B
C
D
E
1 2 3 4 5 6 7 8
A
B
C
D
E
1 2 3 4 5 6 7 8
12
34
5
43
21
1 2 3
www.diyfactory.ru
AD797
PCB v1.0© 2013
Mic Preamplifier
A
B
AD797
AD797(2)62
R
C28
48SW
+15v -15vGnd
v84+
+Out
-Out
GND
Gain
Gain
nI+nI-
dnG
R00 1
k3
R001
k3
33R
k01
k2k2
6k816k81
33R
100n
100n100n
n001n001
p2222p
4u7
4u7
4u7
4u7
220p
2u2/63v
220p2u2/63v
220p
220p
3,0
3,0
3,0
3,0
C5k
10R
+15v -15v 48v0v
12
3
XLR male
1 2
3
XLR female
Chassis
in +
out +
in -out -
AD797 Mic Preinterconnections
R12 - 2k7
R14 - 330RR15 - 180RR16 - 91RR17 - 43RR18 - 27RR19 - 16RR20 - 8R2R21 - 6R2R22 - 4R2R23 - 10R
AD797N
+
-
+VS
-VS OFF
OFF
CO
MP
AD797N
+
-
+VS
-VS OFF
OFF
CO
MP
6k81
6k81
2k2k
33R
33R
100R
3k
100R
3k10k
2u2
2u2
220p
220p
220p
220p
22p
22p
0.1u
0.1u
4u7
4u7
4u7
4u7
0.1u
0.1u
GND
GND
XLR pin1 goes to ground
R13 - 910R
+VS, -VS of AD797 are on pin 7 and 4 (+18v, -18v)
Note:
AD797Mic preamplifier
(Rotary switch gain)
IC13
26
47
158
IC23
26
47
158
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R26
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
C1
C2C3
C4C5
C6
C7
C8
C9
C10
SW
1
1A
23456789101112
C11
C12
C13
C14
C15
C16
+48v
XLR pin3
XLR pin2
XLR pin1 XLR pin1
XLR pin2
XLR pin3
123456789101112
++
++
A
B
C
D
E
1 2 3 4 5 6 7 8
A
B
C
D
E
1 2 3 4 5 6 7 8
12
34
5
43
21
1 2 3
www.diyfactory.ru
AD797
PCB v1.0© 2013
Mic Preamplifier
A
B
AD797
AD797(2)62
R
C28
48SW
+15v -15vGnd
v84+
+Out
-Out
GND
Gain
Gain
nI+nI-
dnG
R00 1
k3
R001
k3
33R
k01
k2k2
6k816k81
33R
100n
100n100n
n001n001
p2222p
4u7
4u7
4u7
4u7
220p
2u2/63v
220p2u2/63v
220p
220p
3,0
3,0
3,0
3,0
+15v -15v 48v0v
12
3
XLR male
1 2
3
XLR female
Front view
R0 is the same resistor as R26 (10k)Don't solder R0 (10k) when using R26,and vice versa.
Chassis
in +
out +
in -out -
AD797 Mic PreinterconnectionsGain Switch Version
R1 - 2k7
R3 - 330RR4 - 180RR5 - 91RR6 - 43RR7 - 27RR8 - 16RR9 - 8R2R10 - 6R2R11 - 4R2R12 - 10R
R0 - 10k (Use R0 OR R26 on AD797 Mic Pre main board)
Example for AD797 preamp:
10k
R2- 910R
Gain Switch v.1.0
R0
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
SW
1
1A
23456789101112
123456789101112
A
B
C
D
E
1 2 3 4 5 6 7 8
A
B
C
D
E
1 2 3 4 5 6 7 8
46.9
mm
87mm
12
34
5
12
34
1 2 3
www.diyfactory.ru
AD797
PCB v1.0© 2013
Mic Preamplifier
A
B
AD797
AD797(2)
R26
C28
48SW
+15v -15vGnd
+48v
+Out
-Out
GND
Gain
Gain
+In
-InG
nd
100R3k
100R3k
33R
10k 2k
2k
6k816k81
33R
100n
100n100n
100n
100n
22p
22p
4u7
4u7
4u7
4u7
220p
2u2/63v
220p2u2/63v
220p
220p
3,0
3,0
3,0
3,0
