Download SoloP Step-by-Step Instructions

 STEP BY STEP INSTRUCTIONS
BASIC INFORMATION
The SoloP Portable Headphone Amp Kit was designed to sound great, look cool, and be fun to build even
if this is your first kit project. Please follow these instructions carefully to ensure your safety and the best
performance of your SoloP!
WARNING
Please read this BEFORE beginning!
This kit requires soldering and the use of a soldering iron. Parts of the
soldering iron get dangerously hot—including everything forward of the
handle. You could hurt yourself or start a fire if you’re not careful. You must be
instructed in the proper and safe use of a soldering iron.
Do not use fingers to hold parts in place while soldering. You can be burned
even though you are soldering on the opposite side of the board. All materials
conduct heat, especially metal. Heat is quickly conducted through the metal
leads.
We strive to provide lead-free circuit boards and components. Everything in the
kit is compatible with lead-free solder. Solder containing lead is toxic. We
always use lead-free solder. It is readily available and no more difficult to use
than the bad stuff.
The SoloP hardware is based on a very popular design for “A Pocket Headphone Amplifier” by Chu Moy.
It’s also called a CMOY amp. For more information you can find his original article on headwize.com.
Another excellent resource is the tutorial at http://tangentsoft.net/audio/cmoy-tutorial/ by Warren
Young.
The SoloP design is open sourced and the design files are licensed for just about any use CC-BY-SA. The
project is archived at Github.
These instructions are copyright © 2014 by Boxed Kit Amps, Ltd.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 1 BEFORE YOU START
TOOLS AND SUPPLIES
Required
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Soldering iron
Solder - thin rosin core solder made specifically for electronics
Screwdriver - #00 Phillips-head
Small diagonal cutters (sprue cutters)
Pliers, regular or needle-nose
Metal file or emery cloth or sand paper
Wire strippers
Digital multimeter
Toothbrush (new is better, old ones are dirty)
Solid, stable work surface
Good lighting
Useful
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Helping hands or PCB vise (Panavise Jr.)
Poster putty
Pencil eraser
Solder sucker and solder wick
Alcohol
Heatproof pad (Silpad)
Magnifying glass or close-up reading glasses
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 2 CHECK YOUR PARTS
Refer to the parts list, schematic, parts placement diagram, and the picture to identify all the parts.
Inspect the circuit boards for damage. Check for cracks, scrapes, holes drilled in the wrong place or plugged
up.
Not shown: battery and case.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 3 PARTS LIST
Part
case
front panel
volume pot
RK09IF
knob
source & output jacks
LED
RLED
SOLOP
IC1
CS
C1, C2
C3, C4
R3, R6
R1, R2, R4, R7
R5, R8
snap clip
battery
foam spacer
rainbow ribbon wire
Description
w/battery compartment
3"x1" acrylic
10K audio w/switch
volume interface board
soft-touch, D-shaft
3.5mm stereo, panel mount
3mm
1K brn-blk-blk-brn-brn
or 10K brn-blk-blk-org-blk
main amp board
op amp, OPA2132PA
chip socket 8-pin DIP
470uF 25V electrolytic
0.47uF polypro film
100K brn-blk-blk-org-brn
4.7K yel-pur-blk-brn-brn
22K red-red-blk-red-brn
for 9V battery, with leads
9V alkaline
3/8"x3/8"x3" closed-cell
26 gauge 10 conductor
Quantity
1
1
1
1
1
2
1
1
1
1
1
2
2
2
4
2
1
1
3"
4"
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 4 PREPARATION
Read instructions first. Heed all warnings.
Work on a solid flat surface. Use something like a Silpad to protect against scratches
and burns.
Clean everything before soldering. A simple pencil eraser, followed by alcohol works well.
All the leads and the backs of the circuit boards should be shiny.
SOME GENERAL BOARD STUFFING NOTES
Prior to stuffing any components, study the schematic, circuit board, and parts list—see how the
same part is represented on each. Understanding the schematic will help you understand the circuit
and the instructions, but it isn’t absolutely required to build the kit.
Insert components from the top (printed side) of the circuit board and solder them on the bottom. As
a general rule, start with the smallest components that lie closest to the board.
The instructions start out very detailed and get less so as you get familiar with the process. Proceed
at your own pace, skim stuff you already know, refer back to stuff you haven’t quite got yet.
SOME SOLDERING TIPS FOR THIS KIT
These notes are meant to be helpful when you already know how to solder and do not substitute for
instruction in the proper and safe use of a soldering iron. Get instruction!
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Clean, clean, clean! Clean is your best friend. Clean all the parts even if they don’t look dirty.
The surface of the metal oxidizes. This oxidized layer not only makes soldering difficult, it is a
significant insulator and can interfere with the electrical connection between the part and the
circuit board. Clean the pads on the circuit board, too. Both sides! More on this below.
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The tip of the soldering iron, as well as the solder already on the tip also oxidizes. That’s why
you need to clean the tip every time you use the iron. By the way, when you’re done for the
day and you go to store the iron, clean the tip first, then coat the tip with a blob of solder. This
will keep the oxidation off the tip and the next time you use the iron, you can just wipe off the
coating of oxidized solder.
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The kit’s circuit boards are “plated through hole” (PTH), meaning that the holes in the board
are plated with metal all the way through. This plating pulls solder into the hole between the
wall of the hole and the lead. Therefore, you don’t need much solder on the surface of the
board. A good solder joint will have a tiny bit of solder showing on both sides of the board.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 5 BUILD THE MAIN AMP BOARD
Locate the SoloP main amp board.
SoloP Parts Placement Guide
The circuit boards are
manufactured in panels where
they are connected by small
sprues. These need to be
snapped off with pliers, and the
scars smoothed with a file or
emery cloth. Check all edges.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 6 INSTALL THE CHIP SOCKET
Start with the 8-pin DIP socket.
Be sure to align the socket such
that the notched end matches
the drawing on the board.
Securely hold the part in place.
Pictured is a “helping hands” —
a very useful tool.
Carefully solder all eight pins.
Start with
a corner, then move to the
opposite corner. After tacking
the chip down by the corners,
the rest of the pins can be
soldered in any order.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 7 IDENTIFY & STUFF THE RESISTORS
Eight (8) resistors go on the main board.
R1, R4 (2) 100KΩ brown-black-black-orange-brown
R2, R5, R7, R8 (4) 4.7KΩ yellow-violet-black-brown-brown
R3, R6 (2) 22KΩ red-red-black-red-brown
K stands for thousand so 4.7K is 4700 ohms. This is also written 4K7, to avoid any confusion over the
decimal point.
This will leave one (1) resistor to go on the volume interface board. You will have one of the following
two resistors in your kit depending on which front panel you have.
RLED (1) 1K brown-black-black-brown-brown
or
RLED (1) 10K brown-black-black-red-brown
Resistors are marked with their
value in colored stripes.
You can use a color chart to pick
a resistor out of the pile.
https://www.google.com/search
?q=resistor+color+code
VERIFY that you have picked the
correct resistor by measuring
with a multimeter.
The resistors supplied with the kit are manufactured to within 1%
tolerance. This means that your reading on the multimeter may be
off by a bit. There is also some error with affordable multimeters.
So, for example, the 4.7K resistors can measure anywhere from
4.65K to 4.75K ohms. In this picture, the meter reads 4.71K ohms.
That’s fine.
This is important because some
resistor color codes make
perfect sense when read
backwards. For example 120
ohms backwards is 10K ohms.
Both are common values. You
may have gotten the wrong
parts!
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 8 On each resistor bend the leads
down at each end. This should
just about match the spacing of
the mounting holes on the
board.
Insert half the resistors into the
board. Use every-other resistor
position (as pictured). You’ll see
why when you flip the board. It
get’s crowded under there.
Spread the leads under the
board to hold the resistors in
place.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 9 Flip the board and solder all the
leads, trimming as you go (if any
get in the way) or all at once
when you are finished.
Install the rest of the resistors in
the same way.
The electrolytic capacitors are
polarized and must be installed
in the correct orientation.
The positive lead is longer and
goes in the hole marked with a
plus (+) sign.
This is important! Please
double check:
The wide stripe is on the side
with the negative lead.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 10 The film caps are not polarized
and can be inserted in either
direction.
However, they have very short
leads, so the trick with spreading
the leads to hold them in won’t
work.
Poster putty works well to
secure them in place until you
can solder them.
Be careful not to melt the putty!
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 11 BUILD THE VOLUME INTERFACE
Locate the RK09IF volume interface board.
RK09IF Parts Placement Guide
The edges of the volume
interface board (RK09IF) need to
be sanded smooth just like the
main amp board.
The last remaining resistor
should be either 1K or 10K
ohms.
Install this in RLED.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 12 Now, install the volume pot,
being careful to line up all the
pins.
Install it on the top of the
board—the side with the
printing on it. It will only go in
one way. Be sure it’s fully
seated.
Friction will hold it until all the
leads are soldered.
The rainbow ribbon wire needs
to be split into groups.
Rather than tear it, which is hard
to control and ends up ragged,
use a blade to slice it apart.
Be careful not to nick the inside
colored insulation. This could
leave a bare spot.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 13 Make pieces that are 1, 2, 2, 2,
and 3 conductors wide (as
pictured).
The color groups shown in the
photo match the wiring diagram.
black
white+gray
violet+blue
green+yellow
orange+red+brown
For each group of wires, split
one end about 1/2” back.
Then, carefully strip 1/16” off
the individual ends.
For the black singleton, strip
1/2” off one end.
On each stripped wire end,
neatly twist the bare strands
together.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 14 “Tin” the wire by applying the
smallest possible amount of
solder.
The plastic insulation may shrink
back due to the heat. It’s OK.
Take the green+yellow pair and
insert the green wire into I 1 and
the yellow into I 2 .
A note about signal names
The amp handles two channels. It doesn’t actually matter which is right or left, as long as they are kept
consistent the whole way through. That’s why they’re simply marked 1 and 2 (S1, I1, O1). In this build
channel 1 is right and 2 is left.
Another point of confusion could be the difference between “source” (S1) and “input” (I1). It was
necessary to distinguish the two wires and it made sense to name the wire that comes from the jack
with the source of the music as the source (S) and the wire that goes to the input of the amp board as
the input (I).
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 15 Flip the volume board assembly,
keeping the wires inserted and
securely in place.
Solder the wires into the board.
Make a good connection, but be
quick so the plastic insulation
doesn’t shrink back too far.
Install the triple group in the
same way. These wires carry
power—brown is V-, red is V+
and orange is 0V.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 16 ASSEMBLE THE FRONT PANEL
Attach a wire pair to each jack.
Refer to the wiring diagram for
color placement.
It helps to tin the contacts on
the jacks with a tiny amount of
solder. Be careful, too much
heat here can melt and ruin
the jack.
With both the wire end and the
contact tinned, simply hold them
touching and briefly apply the
soldering iron just until
everything melts together.
Pictures below might show this better.
Carefully peel the protective
paper from the front panel. You
can do it dry, with just
fingernails.
Thread each wire pair through
the front panel from the front.
Seat the jack into the front
panel, then thread the attaching
nut up along the wire and onto
the back of the jack.
Tighten snugly, but don’t break
the front panel.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 17 The single black wire carries the
common (CMN) signal. It
attaches to the long, centered
terminal on each jack.
Solder the outboard connection
(right jack in photo), then bend
the wire down and solder the
inboard (left jack in photo)
connection.
Install the volume pot in the
front panel by inserting the
shaft from behind and placing
the washer and nut on the front.
The volume pot itself has a
locating tab that fits into a slot
in the front panel.
Lining this up ensures everything
is right side up.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 18 Measure the length of the violet
and blue wires from the source
jack to the S1 and S2 holes on
the volume interface board.
Trim to length, split, strip, and
tin.
Insert the end of the violet wire
into S2 and blue wire into S1
from the top of the board.
Be sure to keep the colors in the
correct positions.
Flip the whole assembly and
solder from below.
Attach the black common wire
to the CMN hole in the same
way.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 19 INSTALL POWER INDICATOR LED
If you have a transparent front
panel, then skip ahead two
frames.
If your front panel is opaque,
then push the LED through the
hole in the front panel from the
rear. Be sure the cathode
(shorter, negative) lead is
toward the circuit board.
This step only applies to opaque front panels with a hole next to
the volume pot. If your front panel is transparent it won’t have a
hole and you can have the LED point wherever you like.
Smash the LED leads down onto
the back of the front panel, into
the corner, and along the side of
the pot.
This get’s the leads out of the
way of one of the mounting
posts inside the case.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 20 With a transparent front panel:
you can bend the leads so the
LED points in any direction you
choose.
In the photo the LED lights up
the back of the front panel.
Be sure the leads don’t touch
each other or anything else that
could cause a short. You can use
some tape to be safe.
The anode (longer, positive) lead
goes in the last hole in the
board. The cathode (shorter,
negative) lead goes into the hole
forward of the last hole.
Trim, insert, and solder the
leads.
In the photo the short lead appears to be longer due to it being on
the inside curve.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 21 COMPLETE WIRING
Layout the front panel and main
board assemblies to match the
wiring diagram.
Note the PC board is backside up
and the long edge with the
notched corner faces the front
panel.
Measure the hookup wires for
length.
Trim the wires.
Prepare the hookup wires by
stripping 1/16” off each end,
tinning the bare leads, and
twisting the input and output
leads for each side.
This is the most important place
to get the channels consistent.
Please double check the wiring
diagram.
In the photo, the blue wire comes from the near side of the source
jack and goes to S1 on the volume interface board.
It’s difficult to see, but the yellow wire then comes out of I1 next to
S1 on the volume interface board, and connects to I1, nearest, on
the main amp board.
The white wire then connects O1, nearest, on the main amp board
As a second check, trace the wire
from one side of the source jack
(the jack with the arrow pointing
in on front panel). Make sure
that the channel number is the
same as it routes from the
source jack to the volume
interface board to the main amp
board to the same side of the
output jack.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 22 to the near side of the output jack.
Insert wires from the bottom
side of the board and solder on
the top.
Insert battery leads into volume
interface board from the top. Be
sure that red goes to B+ and
black goes to B-.
Solder in place from bottom of
board.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 23 The flux left over from soldering
can conduct electricity. It has to
be cleaned off both boards.
Use a toothbrush and water to
remove the flux. If the flux is
being stubborn, you might have
to use alcohol. Read the
instructions that came with the
solder.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 24 PREPARE ENCLOSURE
Some of the turrets (bosses,
nubs) inside the case interfere
with assembly and have to be
removed.
The turrets to remove are the 4
shorter ones closer to the
middle on both the top and
bottom pieces. Be sure to leave
the outer turrets in place.
Use stout side cutters and watch
out for flying debris.
Cut the foam spacer material at
about 2”.
The deeper half of the case is
the top. Install the foam spacers
inside this piece by simply
sticking them to the side and
rear walls.
There should be a battery-sized
space left.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 25 Test before Final Assembly
Attach the battery. It only snaps
in one way, but it’s best not to
even touch the terminals the
wrong way around.
Twist the volume switch
clockwise until it clicks on.
The LED should light.
If not, see the Troubleshooting
section.
Check for proper voltages at the
op amp chip socket.
Set your digital multimeter
(DMM) to measure DC voltage in
the range up to 20 volts.
Attach the negative lead of
DMM to the middle of the 100K
resistors just south of the chip
socket. It’s OK if this shorts them
together; they are connected
here.
Pin 4 = –V = -4.5
Pin 8 = +V = 4.5
Values to within +/-0.5V are
acceptable.
With the notch on the socket facing up, pin 1 is
at the upper-left corner. Pins are numbered
going down, 2, 3, 4, and then across to the
lower-right corner 5, then turning upward 6, 7, 8
at the upper-right corner.
Although the numbering scheme will always be consistent, the
function of each pin will vary for different types of chips.
Turn off the power.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 26 FINAL ASSEMBLY
Safe handling of integrated circuit (IC) chips
The circuits inside the chip are microscopically small and easily damaged by static electric shock. Be
sure to get rid of any static electricity you may have built up on your body. Ground yourself by touching
something large and metal – the leg of your desk, for example.
You can also be safer by touching all the pins at once. This is the idea behind the black conductive
foam. It shorts all the pins to each other, ensuring that they are all at the same voltage and no current
can flow.
Make sure the power is off.
Orient the notch in the chip with
the notch in the socket and
make sure both notches are
aligned with the picture on the
circuit board.
You may have to squeeze the
pins to get them to go into their
holes. Don’t push too hard – you
could bend the pins.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 27 Install the main amp board and
front panel assemblies into the
top half of the case. The top half
is deeper and has a slot for the
main circuit board.
The front panel also fits into a
slot at the front of the case.
Route the battery wires over the
corner notch in the main circuit
board and then behind the screw
boss (a.k.a. turret or tower).
Snug the battery into its space
next to the foam filler. The
battery terminal goes on the end
away from the corner notch.
Carefully line up the bottom half
of the case and install four
screws.
Open the battery compartment
and make sure the battery wires
are not pinched and that the
battery can be easily changed.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 28 To install the knob, find the
flattened part of the hole in the
knob, line it up with the flat on
the shaft, and push the knob
home.
You’ve done it!
Take a moment to admire your
handiwork.
Now, be brave and plug it in!
[See Hookup diagram for help
with this.]
For the first test, you probably
shouldn’t use your expensive
mp3 player as a music source or
your very best headphones to
listen.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 29 HOOKUP DIAGRAM
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 30 !
Wiring Diagram
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | %!!
Main Amp Board Schematic
Volume Interface Board Schematic
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 32 Troubleshooting
Smoke, sparks, oozing, bad smell.
***
If safe, disconnect battery!!!
***
If the electrolytic capacitors leaked and the
board looks salvageable, remove and replace
capacitors double-checking polarity. Clean
the board, of course.
If the capacitors had correct polarity, check
polarity of power supply.
Go through steps for electrical problems.
Replace any burned out components.
Check the music source plugged into the
amp, especially if chip or socket is charred.
No sound.
Check that the battery is installed correctly
and has a charge, on switch is “on”, and
volume is turned up.
Make sure music source plugged into amp is
actually sending a signal.
Make sure headphones are working.
Go through steps for electrical problems.
Case won’t shut all the way.
Make sure no wires are being pinched.
Especially check under the amp board.
Remove everything and make sure the case
closes when it’s empty. If not, see if you can’t
fix it. It may need to be replaced.
Insert front panel backwards so everything
else remains outside. Take it back apart and
trim edges with file if necessary.
Assemble with amp board in place, but front
panel hanging out the front. Disassemble
and trim edges with file if necessary.
Power voltages are wrong.
Make sure battery is good. Measure its
voltage. Should be at least 8.4 volts. Be sure
it’s snapped in all the way.
Volume switch is turned past its “on” click.
Inspect wires for pinching.
Go through steps for electrical problems.
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 33 Electrical problems.
Terrible scratchy sounds, static, buzzing,
squealing, etc.
Go through wiring diagram making sure all
components are installed in correct position,
orientation, and value. Make sure all wires
are connected properly.
Double check that the op amp is installed in
the right direction. The chip socket could be
installed backwards, so be sure to align it
according to the circuit board.
Inspect boards using an illuminated
magnifying glass.
Look for short circuited or broken traces or
leads.
The solder flux can actually conduct enough
current to cause short circuits. Remove all
flux with alcohol and toothbrush, cleanroom
swabs, and toothpicks.
Look for what’s called cold solder joints.
That’s where the solder didn’t stick properly.
A good joint is pretty. It is smooth and joins
smoothly into lead and board. Anything that
looks ugly or suspicious should simply be
remelted.
Failing everything else, melt all the joints
just to be sure.
Still doesn’t work.
Drive to coast. Huck amp into water.
Consider a new hobby, like fishing.
Just kidding. You should have a look at
Chu Moy’s original article on headwize.com
SOLOP HEADPHONE AMP KIT STEP-BY-STEP | 34