AkitikA PR-101 User manual

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PR-101STEREOPREAMPLIFIER
PhonoPreamp
ASSEMBLYMANUAL
© 2015 AkitikA LLC
All rights reserved
Revision 1p15 July 4, 2015

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Table of Contents
Table of Contents................................................................................................................ 2
Table of Figures.................................................................................................................. 2
Section 1: About This Manual............................................................................................ 4
Who Should Attempt this Project? ................................................................................. 4
Tools you’ll need ............................................................................................................ 4
Helpful Tools.................................................................................................................. 4
Project Overview ............................................................................................................ 4
Important Safety Notes................................................................................................... 5
About Components ......................................................................................................... 5
Recommended Solder..................................................................................................... 5
Warranty ......................................................................................................................... 5
Section 2: Kit Building Hints.............................................................................................. 6
Section 3: Building the Phono Preamp............................................................................... 7
Component Order............................................................................................................ 7
Install the Resistors......................................................................................................... 8
Install the small non-polarized capacitors....................................................................... 9
Install the bypass capacitors............................................................................................ 9
Install the Integrated Circuits........................................................................................ 10
Install film capacitors.................................................................................................... 10
Install the Electrolytic (polarized) Capacitors .............................................................. 11
Install the Selector Jumpers.......................................................................................... 11
Install the Power Wires................................................................................................. 12
Install the Signal Wires................................................................................................. 13
Install Connectors and Front Panel............................................................................... 14
Install Mounting Brackets............................................................................................. 15
Section 5: Configure the Options...................................................................................... 16
Cartridge Loading......................................................................................................... 16
High-Pass Filter Setting................................................................................................ 17
Gain Setting .................................................................................................................. 18
Section 5 – Installing the Phono Preamp into the PR-101................................................ 19
Mechanical Installation................................................................................................. 19
Power Connections ....................................................................................................... 19
Signal Connections ....................................................................................................... 20
Section 6: Tests and Final Assembly................................................................................ 21
Section 7: Hooking Up a Turntable.................................................................................. 21
Section 8: About the Phono Preamp................................................................................. 22
Specifications................................................................................................................ 22
Appendix 1 – Shielded Cable Preparation........................................................................ 23
Table of Figures
Figure 1-Empty the power supply components into a soup bowl....................................... 7
Figure 2-Silk screen shows phono preamp component locations....................................... 7
Figure 3-Prepare 12" length of Red/Black Zip cord (drawing not to scale)..................... 12
Figure 4-Close-up showing installation of power, ground and signal wires .................... 12

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Figure 5-Hardware detail for installing the RCA Jacks and insulating washers into the
faceplate............................................................................................................................ 14
Figure 6-Install both jacks, noting orientation of ground lugs, color stripes, and solder
terminal............................................................................................................................. 14
Figure 7-Install the mounting brackets............................................................................. 15
Figure 8-No additional capacitive loading is selected with the short plugs as shown here
........................................................................................................................................... 16
Figure 9-Left Channel and Right Channel High Pass Jumpers........................................ 17
Figure 10-P6 sends left channel gain, P5 sets right channel gain..................................... 18
Figure 11-Phono stage installed but power and signal not yet routed and connected...... 19

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Section 1: About This Manual
This manual gives the information needed to build and use the moving magnet phono
preamplifier for Akitika LLC’s PR-101 Stereo Preamplifier.
Who Should Attempt this Project?
You can build this kit if you can:
1. Solder (using normal rosin core solder and a soldering iron).
2. Use simple hand tools like screwdrivers, wire cutters, and pliers.
3. Read and follow directions.
It helps if you:
1. know a bit about electronics, or
2. have a friend who knows a bit about electronics
3. can get to YouTube to watch a few helpful videos about the assembly process
(none are posted as of this version of the manual).
Tools you’ll need
You’ll need the following tools:
1. Phillips screwdriver (#1 and #2)
2. Pliers or nut drivers suitable for #4 and #6 hardware
3. needle nose pliers (helpful, but not strictly necessary)
4. pencil type soldering iron of 25 to 50 Watts (no huge honking soldering guns or
blowtorches)
5. wire cutters and strippers
6. multi-meter to measure power supply voltages and confirm resistor values
(strongly recommended)!
Helpful Tools
These tools aren’t strictly necessary, but make building the kit easier.
1. magnifying glass, if you’re over 42!
2. lead bending jig to form axial component leads to the correct span for insertion in
the PCB.
Project Overview
The project consists of the following steps:
1. Building the phono preamp circuit board.
2. Configuring the loading, gain, and highpass options.
3. Installing the phono preamp into a PR-101 preamplifier.

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Important Safety Notes
By purchasing, using, or assembling this kit, you have agreed to hold Akitika LLC
harmless for any injuries you may receive in its assembly and/or use. To prevent injuries:
Wear safety glasses when soldering or clipping wires to prevent eye injuries.
Always unplug the power before working on the amplifier.
Large capacitors hold lots of energy for a long time. Before you put your hands
into the amplifier:
oPull the AC plug!
oWait 2 full minutes for the capacitors to discharge!
Remove jewelry and rings from your hands and wrists, or anything that might
dangle into the amplifier.
If working one the equipment with the power on, keep one hand in your pocket,
especially if you’re near the power supply or power supply wires. This can
prevent serious shocks.
Build with a buddy nearby. If you’ve ignored all the previous advice, they can
dial 911 or get you to the hospital.
Read and understand the safety manuals of all the tools you use.
About Components
We reserve the right to make design/or component changes at any time without prior
notification.
Recommended Solder
The kit must be assembled with 60/40 Rosin Core solder. The recommended diameter is
0.032 inches. Among many such sources of solder, I have used Radio Shack part number
64-009. It contains 8 oz. of solder, which is much more than you’ll need to assemble the
PR-101 kit.
Warranty
With the exception of fuses, Akitika will replace for free any parts of a correctly
assembled product that fails within one year of the date of purchase when the equipment
has been used in home stereo applications. It is the responsibility of the kit builder to
install the replacement part(s). This warranty applies to the original purchaser only. It
does not apply to units that have been physically or electrically abused, modified without
prior factory authorization, or assembled with other than 60/40 Rosin Core solder.
Akitika LLC’s liability shall in no event exceed the cost paid to Akitika LLC for the kit.

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Section 2: Kit Building Hints
Yes, I know you want to ignore this section, and jump right into building the kit.
However, please take a minute and read the advice of this section. I’ve condensed it into
bullets so that even you guys who are in a hurry can benefit.
Stop any time you’re feeling confused, tired, or anxious. Taking breaks at those
strategic times will keep the build enjoyable and greatly enhance your chances of
first-time success.
A soup bowl is your friend. Before you build a board, carefully empty the parts
into a broad, flat, light colored soup bowl. That makes it easy to find the parts,
and keeps them from getting lost.
A digital ohm-meter is an easy way to make sure that you’ve picked the right
resistor. It’s a great cross-check on the resistor color code. Measure twice and
solder once!
A lead-bending jig can make for quicker, neater assembly. It’s certainly not
necessary.
Is something in this manual confusing? Does something look wrong? Send your
questions by email to [email protected]om. You’ll help yourself and everyone who
builds the kit.

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Section 3: Building the Phono Preamp
This section details the process of building the phono preamp circuit board. Begin by
carefully emptying the contents of the parts envelope into a broad soup bowl, as shown
below. In general, you’ll start with the components that lay closest to the board, working
your way towards the taller components.
Figure 1-Empty the power supply components into a soup bowl
Figure 2-Silk screen shows phono preamp component locations
Component Order
You’ll notice that the component designations in the directions don’t go exactly in order.
We have grouped them so that all components with the same value appear together. This
makes assembly easier. You’ll find in the parts kit that similar parts, e.g. 3 1K resistors,
are typically (though not always) taped together.

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Install the Resistors
In general, you install axial leaded components (like the resistors) by placing the body on
the silk screen side of the board, and the leads through the indicated holes. Bend the leads
over on the back of the board to keep the resistors from falling out until your solder them
in place. Try to bend the leads in a direction that won’t lead to solder bridges between
traces that should remain disconnected.
We recommend the following procedure:
1. Insert all components of the same value or type
2. Bend the leads as described above.
3. Solder the leads on the back of the board.
4. Clip the leads.
Track your progress by placing a check-mark in the done column as you install each
component. Bend resistor leads to 0.45” width
Designation Value Color Code Done

R43 1K Brown, Black, Black, Brown, Brown
R44 1K Brown, Black, Black, Brown, Brown
R45 1K Brown, Black, Black, Brown, Brown
R46 1K Brown, Black, Black, Brown, Brown
R6 1K18 Brown, Brown, Grey, Brown, Brown
R19 1K18 Brown, Brown, Grey, Brown, Brown
R31 1K18 Brown, Brown, Grey, Brown, Brown
R32 1K18 Brown, Brown, Grey, Brown, Brown
R15 1M00 Brown, Black, Black, Yellow, Brown
R16 1M00 Brown, Black, Black, Yellow, Brown
R3 221 Red, Red, Brown, Black, Brown
R20 221 Red, Red, Brown, Black, Brown
R21 221 Red, Red, Brown, Black, Brown
R30 221 Red, Red, Brown, Black, Brown
R37 23K2 Red, Orange, Red, Red, Brown
R38 23K2 Red, Orange, Red, Red, Brown
R39 24K9 Red, Yellow, White, Red, Brown
R40 24K9 Red, Yellow, White, Red, Brown
R22 2K00 Red, Black, Black, Brown, Brown
R12 2K00 Red, Black, Black, Brown, Brown
R13 2K00 Red, Black, Black, Brown, Brown
R26 2K00 Red, Black, Black, Brown, Brown
R9 31K6 Orange, Brown, Blue, Red, Brown
R29 31K6 Orange, Brown, Blue, Red, Brown
R41 412 Yellow, Brown, Red, Black, Brown
R42 412 Yellow, Brown, Red, Black, Brown
R5 4K22 Yellow, Red, Red, Brown, Brown
R14 4K22 Yellow, Red, Red, Brown, Brown

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R35 590 Green, White, Black, Black, Brown
R36 590 Green, White, Black, Black, Brown
R2 5K23 Green, Red, Orange, Brown, Brown
R25 5K23 Green, Red, Orange, Brown, Brown
R10 5K62 Green, Blue, Red, Brown, Brown
R27 5K62 Green, Blue, Red, Brown, Brown
R1 63K4 Blue, Orange, Yellow, Red, Brown
R23 63K4 Blue, Orange, Yellow, Red, Brown
R33 825 Grey, Red, Green, Black, Brown
R34 825 Grey, Red, Green, Black, Brown
R8 8K06 Grey, Black, Blue, Brown, Brown
R28 8K06 Grey, Black, Blue, Brown, Brown
R4 68K1 No load
R18 68K1 No load
R7 150K No load
R24 150K No load
R11 Not present
R17 Not present
Note: save some of the longer cut resistor leads. You’ll use them in one of the final
assembly steps to connect the RCA jacks to the PCB.
Install the small non-polarized capacitors
The capacitors you’ll install in this section can be installed in either orientation. Please
leave C22 and C40 for last in this section.
Small Value COG dielectric Capacitors
Designation Value Rating, Marking, Description Done? ()
C2 100 pF COG, 101K, axial leads
C5 100 pF COG, 101K, axial leads
C50 100 pF COG, 101K, axial leads
C57 100 pF COG, 101K, axial leads
C13 27 pF COG, 270K, axial leads
C1 27 pF COG, 270K, axial leads
C4 47 pF COG, 47J, axial leads
C12 47 pF COG, 47J, axial leads
C22 10 pF COG, 100, blue radial leaded package
C40 10 pF COG, 100, blue radial leaded package
Install the bypass capacitors
The 0.1 uF bypass capacitors a not polarized, and can be inserted with either orientation.
Non Polarized Bypass Capacitors (Location Hint: a pair of these surrounds each IC)
Designation Value Rating, Marking Done? ()
C14 0.1 uF Bypass, 104, radial leads
C15 0.1 uF Bypass, 104, radial leads
C16 0.1 uF Bypass, 104, radial leads

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C17 0.1 uF Bypass, 104, radial leads
C28 0.1 uF Bypass, 104, radial leads
C29 0.1 uF Bypass, 104, radial leads
C31 0.1 uF Bypass, 104, radial leads
C33 0.1 uF Bypass, 104, radial leads
C42 0.1 uF Bypass, 104, radial leads
C44 0.1 uF Bypass, 104, radial leads
C45 0.1 uF Bypass, 104, radial leads
C47 0.1 uF Bypass, 104, radial leads
Install the Integrated Circuits
Integrated Circuits (watch pin 1 location)
Designation Description Done? ()
U1 NE5534 single opamp, 8 pin dip package
U2 NE5534 single opamp, 8 pin dip package
U3 NE5532 dual opamp, 8 pin dip package
U4 NE5532 dual opamp, 8 pin dip package
U5 NE5532 dual opamp, 8 pin dip package
U6 NE5532 dual opamp, 8 pin dip package
Install film capacitors Nonpolar Film Capacitors
Designation Value Rating, Marking, Description Done? ()
C51 0.1 uF Film, 100n, small box, radial leads
C49 0.1 uF Film, 100n, small box, radial leads
C38 0.33 uF Film, .33J63, radial leads
C10 0.33 uF Film, .33J63, radial leads
C7 1 uF Film, 1J63, radial leads
C8 1 uF Film, 1J63, radial leads
C9 1 uF Film, 1J63, radial leads
C20 1 uF Film, 1J63, radial leads
C26 1 uF Film, 1J63, radial leads
C27 1 uF Film, 1J63, radial leads
C37 1 uF Film, 1J63, radial leads
C39 1 uF Film, 1J63, radial leads
C21 10 nF Film, 10nJ100, radial leads
C32 100 nF Big Film cap, µ10F400, radial leads
C36 100 nF Big Film cap, µ10F400, radial leads
C41 100 nF Big Film cap, µ10F400, radial leads
C43 100 nF Big Film cap, µ10F400, radial leads
C56 2.2 nF Film, 2n2, radial leads
C48 2.2 nF Film, 2n2, radial leads
C55 2.2 uF Film, 2.2J63, radial leads
C25 2.2 uF Film, 2.2J63, radial leads

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C34 22 nF Film, 22n, radial leads
C53 22 nF Film, 22n, radial leads
C35 3.3 nF Film 3n3J100, radial leads
C52 3.3 nF Film 3n3J100, radial leads
C54 33 nF Film, 33nF, radial leads
C30 33 nF Film, 33nF, radial leads
Install the Electrolytic (polarized) Capacitors
Polarized Capacitors (watch polarity)
Designation Value Rating, Marking Done? ()
C3 220 uF Electrolytic capacitor, 220 uF 35 V, radial leads
C11 220 uF Electrolytic capacitor, 220 uF 35 V, radial leads
C6 220 uF Electrolytic capacitor, 220 uF 35 V, radial leads
C23 220 uF Electrolytic capacitor, 220 uF 35 V, radial leads
C24 220 uF Electrolytic capacitor, 220 uF 35 V, radial leads
C46 220 uF Electrolytic capacitor, 220 uF 35 V, radial leads
C18 22 uF Electrolytic capacitor, 22 uF 35 V, radial leads
C19 22 uF Electrolytic capacitor, 22 uF 35 V, radial leads
Install the Selector Jumpers
Install the selector pin fields using the following check-list. Hint: Begin by soldering just
one corner pin to make sure the pin-field sits straight and level. That makes it easy to re-
heat and adjust the pin-fields if they’re a bit crooked. Once the pin fields are straight,
solder the remainder of the pins.
Selector Pin Fields
Designation Description Done? ()
P2 3x2 pin field for left channel cartridge loading. Insert the
short side into the PCB.
P3 3x2 pin field for right channel cartridge loading. Insert the
short side into the PCB.
P1 2x2 pin field. Insert the short side into the PCB.
P4 2x2 pin field. Insert the short side into the PCB.
P7 2x2 pin field. Insert the short side into the PCB.
P8 2x2 pin field. Insert the short side into the PCB.

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P5 2x5 pin field. Insert the short side into the PCB.
P6 2x5 pin field. Insert the short side into the PCB.
Install the Power Wires
Prepare a 12” length of red/black zip cord as shown below. Twist the ends tightly, and tin
them.
Figure 3-Prepare 12" length of Red/Black Zip cord (drawing not to scale)
Prepare a 12” length of 18 AWG Green wire. Twist and tin the ends as shown here:
Power Wiring
Task Done? ()
Insert Red wire of Red/black pair into component side of PCB hole marked
POS12V in TB1. Solder on the solder side.
Insert black wire of Red/black pair into component side of PCB hole
marked NEG12V in TB1. Solder on the solder side.
Insert green wire into component side of PCB hole marked GND in TB1.
Solder on the solder side.
Figure 4-Close-up showing installation of power, ground and signal wires

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Install the Signal Wires
Signal Wiring (Right Channel Connections)
Task Done? ()
Cut a 6” length of shielded cable that will be used for the right channel
connections.
Prepare the ends as shown in Appendix 1. Reserve the outer jacket removed
when you exposed the ends.
Cut the black wire at both ends of the shielded cable.
Strip, twist and tin the remaining red ends (2 places)
Twist and tin the drain wire at both ends.
Cut a ½” length of the outer jacket and slip it over the drain wire.
Insert the red wire into the component side of the PCB, into the Right
Output terminal of TB2.
Insert the drain wire (with the outer jacket covering) into the component
side of the PCB, into the Ground of TB2.
Signal Wiring (Left Channel Connections)
Task Done? ()
Cut a 6” length of shielded cable that will be used for the left channel
connections.
Prepare the ends as shown in Appendix 1. Reserve the outer jacket removed
when you exposed the ends.
Cut the red wire at both ends of the shielded cable.
Strip, twist and tin the remaining black ends (2 places)
Twist and tin the drain wire at both ends.
Cut a ½” length of the outer jacket and slip it over the drain wire.
Insert the black wire into the component side of the PCB, into the Left
Output terminal of TB5.
Insert the drain wire (with the outer jacket covering) into the component
side of the PCB, into the Ground of TB5.

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Install Connectors and Front Panel
Install the RCA jacks into the faceplate using the details of Figure 5 and Figure 6.
Figure 5-Hardware detail for installing the RCA Jacks and insulating washers into the faceplate
Jack Installation
Task Done? ()
Install the jacks using insulating washers as shown in Figure 5 and Figure 6.
Note that the locations of the RED and BLACK rings on the RCA jacks.
Fasten the faceplate to the PCB using two 4-40x1/4” sem screws (they have
a built-in lockwasher) as shown in Figure 6.
Complete the jack wiring as shown in Figure 6, a total of 4 wires. Use spare
ends from resistor and capacitor leads to make the connections.
Figure 6-Install both jacks, noting orientation of ground lugs, color stripes, and solder terminal

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Install Mounting Brackets
Install the two mounting brackets using 6-32x1/4” sem screws as shown in Figure 7.
Figure 7-Install the mounting brackets

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Section 5: Configure the Options
Cartridge Loading
Capacitive loading of the cartridge changes its frequency response. Typical RCA phono
cables have a capacitance of about 17 pF/foot. You can add to this capacitance by
selecting jumpers on P2 and P3.
As an example, the Shure M97E is said to have improved sound with 200 pF of loading.
Given 3 foot cables, there would be 51 pF of loading from the cables. You’d then add
another 147 pF, for a total of 198 pF to optimize its loading.
Figure 8-No additional capacitive loading is selected with the short plugs as shown here
The additional capacitive loading is the sum of the selected values:
100 pF 47 pF 27 pF Total Additional
Loading (pF)
Not selected Not selected Not selected 0
Not selected Not selected selected 27
Not selected selected Not selected 47
Not selected selected selected 74
selected Not selected Not selected 100
selected Not selected selected 127
selected selected Not selected 147
selected selected selected 174
Notes:
1. To select a capacitor, install the shorting plug to bridge both terminals on a line
with the capacitance designation.
2. Recommended default: 100 pF
3. To not select a capacitor, install the shorting plug to only contact one terminal on
a line with the capacitance designation, that terminal being the one farthest from
the capacitance designation. See Figure 8.
All the shorting plugs will be used, even if some of the shorting plugs for capacitor
loading are in the storage position (described in 3 above) rather that the active position.

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High-Pass Filter Setting
A turntable can generate extreme low frequency signals that really aren’t part of the
music. Depending on your turntable, amp, and speakers, it may be beneficial to reduce
some of this extreme low frequency information. The following table shows the jumper
settings and the various low frequency responses that they produce.
Figure 9-Left Channel and Right Channel High Pass Jumpers
P7 (and P8) give a highpass response that is:
-3 dB at 20 Hz when pins 1 and 2 are connected by a shorting plug.
-3 dB at 2.5 Hz when pins 4 and 3 are connected by a shorting plug.
P4 and P1 further modify the highpass response:
Not at all, e.g. this filter is flat, when pins 1 and 2 are connected by a shorting
plug.
By adding a 3rd order Bessel Filter that is -3 dB at 20 Hz (and quite a bit farther
down at the critical warp region below 10 Hz).
You must install one shorting plug in each of P1, P8, P4, and P7 for proper operation.
Recommended Defaults:
P7 join pins 3 and 4
P4 join pins 3 and 4
P8 join pins 3 and 4
P1 join pins 3 and 4

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Gain Setting
This phono preamp was made to use with moving magnet cartridges. Moving magnet
cartridges provide around 5 mV at 5 cm/sec at 1 kHz, and are meant to be loaded by 47 K
Ohms.
Figure 10-P6 sends left channel gain, P5 sets right channel gain
It’s hard to say what gain setting will be best for your system in advance. In general, it’s
best to use the lowest gain setting that provides adequate volume for your equipment and
listening situation.
You must install one shorting plug in each of P5 and P6 for proper operation.
Recommended Defaults:
P5 in the 3 dB position
P6 in the 3 dB position
We recommend using the 3 dB setting of P5 and P6 as a starting point. If, with this
setting, you find that the volume control is cramped toward the low-end, you can change
to the 0 dB setting. If the volume control is too far toward the high end, you can change
to gain settings of 6, 9, or 12 dB.
It is possible to access and change all of the options after the phono preamp has been
installed without removing the phono preamp.

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Section 5 – Installing the Phono Preamp into the PR-101
Make sure that the power is disconnected from the PR-101 before proceeding with the
installation.
Figure 11-Phono stage installed but power and signal not yet routed and connected
Mechanical Installation
Please protect the paint finish on your PR101. Be sure to put a towel onto your work
surface prior to laying your PR101 on your work bench.
Remove the cover plate from the Exp 1 Slot and save the two mounting screws.
Butt the phono preamp faceplate to the inside of the front panel. Line up the two
mounting holes in the back panel with those in the phono preamp faceplate. Hold the
phono preamp in place using the two mounting screws that previously held the cover
plate.
Fasten the two mounting brackets to the bottom of the chassis using two 6-32x1/4” sem
screws, inserted from the bottom of the chassis into the mounting brackets.
Power Connections
Connecting +/-12V power to the phono preamp can be done without removing the power
supply board from the PR-101. In a previous step, you tinned the power wires. This
makes it easy to solder them into the power supply PCB. Insert the wires from the
component side, leaving about 1/8” of un-insulated wire above the PCB. This leaves
room to apply the tip of the soldering iron simultaneously to the PCB lands and the wire,
so the solder will melt and a good connection formed.
You can select any of the unused +/-12 terminal sets on the power supply board. We
recommend using TB1. If you followed the PR-101 Assembly instructions, TB3 and TB4
are already used.

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Please note the following
1. Use the recommended order, installing green wire first to minimize damage to
adjacent power wires as you solder them in place.
2. Remove the end of the control cable where it connects to the tone volume board
and fold it out of the way to avoid damaging it with your soldering iron.
3. While soldering, keep the wires straight as they approach the board. This will
keep the insulation from peeling back as you solder.
Power Wiring
Task Done? ()
Insert the green wire into component side of the power supply PCB into the
PCB hole marked AGD on TB1. Solder from the component side.
Route the Red/Black pair and the green wire from the phono preamp power
connector (TB1) along the chassis floor, next to the stand-offs for the
tone/volume board, on the front panel side of the stand-offs.
Insert Red wire of Red/black pair into component side of the power supply
PCB into the PCB hole marked P12 on TB1. Solder from the component
side.
Insert black wire of Red/black pair into component side of the power supply
PCB into the PCB hole marked N12 on TB1. Solder from the component
side.
Signal Connections Right Channel Signal Wiring
Task Done? ()
Locate the shielded cable coming from the right channel output of the phono
preamp. It has a red wire and a drain wire.
Cover the drain wire with a ½” length of the previously reserved outer
jacket. Insert the bare end of the drain wire into the component side of
TB6’s GND pin on the input selector board and solder it in place from the
component side.
Insert the bare end of the red wire into the component side of TB6’s RT pin
on the input selector board and solder it in place from the component side.
Left Channel Signal Wiring
Task Done? ()
Locate the shielded cable coming from the left channel output of the phono
preamp. It has a black wire and a drain wire.
Cover the drain wire with a ½” length of the previously reserved outer
jacket. Insert the bare end of the drain wire into the component side of
TB5’s GND pin on the input selector board and solder it in place from the
component side.
Insert the bare end of the black wire into the component side of TB5’s LT
pin on the input selector board and solder it in place from the component
side.