OSKITONE OKAY Synth User manual
© 2018 Oskitone
For
OKAY Synth DIY Kit
Version 1.1.1
http://www.oskitone.com/product/okay-synth-diy-kit
OKAY 2 Synth DIY Kit Version 2.1
http://www.oskitone.com/product/okay-2-synth-diy-kit
Last updated 2018-02-18
All rights reserved. This book or any portion thereof may not be reproduced
or used in any manner whatsoever without the express written permission
of the publisher except for the use of brief quotations in a book review.
http://www.oskitone.com/
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Hello!
Thank you and congrats on your new OKAY DIY Kit!
Please let me know how it goes, what you think, and/or if you run
into any trouble. Reach me at [email protected].
You can also find last minute guide updates, extra assembly
information, and videos at http://www.oskitone.com/guides
Otherwise, good luck, take your time, and have fun!
-Tommy
Hey, OKAY!
The OKAY is a monophonic, analog, square-wave synthesizer.
It is intentionally minimal.
●Monophonic: Only one note at a time can be played.
This is opposed to “polyphonic,” where multiple
simultaneous notes can be played.
●Analog: There are no computers, microcontrollers,
sound samplers, or anything digital involved. The sound
you hear is the sound of a speaker being abused by
discrete electronic components like capacitors and
resistors and logic chips.
●Square-wave: When its output is viewed on an
oscilloscope, its wave resembles a square. It’s a “hard”
sounding wave type, great for bass lines, and
commonly associated with chiptune music and old
video games
OKAY versions
There are two versions of the OKAY:
●OKAY 1
(Also just called “OKAY” since it came out first)
One octave of keys (13 keys)
●OKAY 2
Two octaves of keys (25 keys) and ¼” audio out jack
This assembly guide is for both versions. Instructions that are
specific to one version and not the other will be noted.
Table of Contents
1. 3D-Printing instructions
a. Slicing
b. Post-printing
2. What’s in the box
a. Inventory
b. Tools (not in the box)
3. Enclosure assembly
4. PCB assembly
a. General tips
b. Connecting wires
c. Wiring diagram
d. 386 0.1.1
i. Wiring the ¼” jack (for OKAY 2 only)
e. 555_4040 01.1.1
i. Wiring the rotary switch
f. bus 0.1.1
i. Polarity on middle pads
g. SPST_VR 0.2.2
i. Wiring for OKAY 2
5. Putting it all together
a. Testing and debugging
b. Final assembly
c. Tuning
d. Care
6. Appendix: Circuit schematics
3D-Printing instructions
If you bought the kit with the 3D-printed parts included, you
can skip this part!
Slicing
Normal .2mm layer height is fine.
Part
Supports
Infill
Color change
Bottom
Build plate only
Normal
n/a
Top
No
Normal
n/a
Hinge parts
No
Normal
n/a
OKAY hold-in
No
Normal
n/a
Keys
No
Light
12.8 / 13.8 ***
Key plungers
No
Normal
n/a *
Speaker
No
Normal
5.4
Labels
No
Normal
6.4
OKAY text
No
Light
9.8 / 9.4 ***
Knobs
No
Normal
18.4
Key cradle
No
Normal
n/a **
* key plungers are only for OKAY 1
** key cradle is only for OKAY 2
** first value is for OKAY 1, second is for OKAY 2
Refer to http://oskitone.com/guides for additional instructions.
Printing
●The enclosure models are pretty big and so can be
prone to warping or curling up from the print bed over
time. Minimize that risk by using a filament with low
shrinkage like PLA and ensuring good bed adhesion.
●The keys have hinges that fragile. Remove them gently
with a scraper tool if they’re stuck to the bed.
Post-printing
1. Clean up strings
a. Cut or melt away any stringing. Be careful not to
scratch dark filament underneath text
embossing
2. Remove built-in supports
a. Break built-in bridge supports from each PCB
post with a small screwdriver or other stabby
object
b. For the OKAY 2, do the same for the key cradle
3. Knobs
a. Cut built-in bridge support from bottom to
expose shaft cavity
b. One knob has a hole in its side. This is a cavity
for the brass threaded insert, which you’ll lock
into place by inserting with a hot soldering iron
What’s in the box
Inventory
●PCB kits
○bus 0.1.1
○555_4040 0.1.1
○386 0.1.1
○SPST_VR 0.2.2 15
○
OKAY 2 upgrade parts (only if OKAY 2)
●3D-printed parts
○Bottom
○Top
○Hinge links (4)
○Latches (2)
○Key overlays
○Key plungers (13)
(OKAY 1 only)
○OKAY text
○OKAY text hold-in tab
○Speaker grill
○Knobs (2: 1 w/ tension screw, 1 w/o)
○Knob labels
○
Key cradle (OKAY 2 only)
○Filament (7”)
●Miscellaneous
○4-40 ¼” screws
■
OKAY 1: 16 / 17*
■
OKAY 2: 6 / 7*
○4-40 ⅜” screws
■
OKAY 1: 0
■
OKAY 2: 23
○4-40 hex nuts
■
OKAY 1: 16
■
OKAY 2: 29
○Twisted 2-conductor wire
■
OKAY 1: 33”
■
OKAY 2: 38”
○
Threaded brass insert *
* If you’re 3D-printing the parts yourself, your kit will come with an extra ¼”
screw and one threaded brass insert.
Tools (not in the box)
You’ll also want to confirm you have these tools
●Required
○Soldering iron and solder
○Wire cutters or diagonal cutters
○Needle-nose pliers
○Philips screwdriver
○Precision flathead screwdriver
○Chromatic instrument tuner
○Elmer’s glue
○9v battery
○Ruler for measuring wire
●Recommended
○Multimeter for debugging
○Wire stripper
○PCB vice or “helping hands” holder
○“Solder sucker” or desoldering braid
○Tweezers or “dentist’s tools” for working with
small components
○Hot glue
○Zip ties for tidying up wires
○Utility knife
○Jumper wires, alligator clips, and an assortment
of different resistors, capacitors, and
potentiometers for experimentation
Enclosure assembly
1. Back hinges
a. With one hand, hold an anchor link into its
cavity on the enclosure bottom
b. With the other hand, thread filament through
holes
c. Repeat for all hinge links, cutting filament with a
small amount of slack (maybe 1/16”)
d. Put the enclosure top on, and repeat
2. Front clasps
a. Just like you did for the hinges on the back,
thread the clasps onto the front with filament.
There are no separate link parts
3. OKAY text
a. Place the OKAY text into its place on the
enclosure top
b. Secure its underside with the hold-in tab
4. Keys
a. For the OKAY 1:
i. Pull the key overlays in through the top
of the enclosure and affix onto the row
of dovetails. Gently push into place
ii. Using a smalls screwdriver in its holed
tabs, pull the keys more securely onto
the enclosure top
b. For the OKAY 2:
i. You’ll first need to solder the SPST_VR
PCBs, so skip this part for now and
follow assembly instructions later.
5. Key plunger pegs
(for OKAY 1 only)
a. With the lid open and the key underside facing
up, carefully drop a small amount of glue into
each of the peg cavities
b. Gently twist each peg into its cavity
(The plastic on these pegs is thin and fragile. If
you break one, the glue will still hold it in place,
but still try not to!)
6. Secure hinge and clasp filament
a. Optionally, secure the hinge and clasp filament
in place with either a dab of glue or by melting it
in place with a soldering iron. (Do the latter in a
well-ventilated space, please.)
7. Finish OKAY text
a. With the enclosure closed and the OKAY text
secured by both its hold-in tab and the key
overlays, put a small amount of glue in the
cavities in its “O” and “A” letters
b. Place the corresponding filler pieces into each
cavity
c. Wipe up any residue glue and leave to dry
PCB assembly
General tips
●Soldering
This guide assumes you already know how to solder. If
you don’t, don’t worry! There are plenty of really good
guides online; I recommend the “Adafruit Guide To
Excellent Soldering”.
●IC chips are static-sensitive
The included IC chips, especially the CD4040, can be
damaged by static electricity. Leave them in their
packaging until ready to install. Before handling,
discharge any static electricity on your body by
touching a large piece of metal
●Ceramic and electrolytic capacitors
There are two kinds of “caps” used in this kit. Ceramic
capacitors are small, circular, and have no polarity;
they can be placed in either direction. Electrolytic caps
are bigger, cylindrical, and have marked +/- polarities.
●Component naming conventions
For these PCBS, C = capacitor, R = resistor. Headers are
typically labelled what they are.
●Vertical resistors
To save space, all the resistors stand vertically instead
of lay flat on the PCB
●Capacitor footprints are small
Also to save space, the capacitors all have soldering
holes that are just slightly too close. You’ll have to pull
them through from the PCB’s underside with pliers. I’ll
fix this in future iterations.
●Component polarities
Some components like LEDs, batteries, and electrolytic
capacitors have positive and negative leads. The PCB
will be labeled where each lead goes, if applicable.
●Wire polarity
This kit includes 2 conductor twisted wire, which you’ll
use to connect the various boards together. To ensure
polarities match between connections, a good
convention is to have the lighter wire be positive and
the darker wire negative.
●Resistor and capacitor labeling
Resistors use a color code to denote their value and
ceramic capacitors have a number system. Where
appropriate, the color or number will be noted for your
reference so you can choose the right one.
●Bypass capacitors
All the ICs use what’s called a bypass or decoupling
capacitor to prevent noise from other parts of the
circuit or even from the power itself from affecting its
IC.
●ICs in sockets
Each IC chip comes with a corresponding socket with
the same number of pins. You will solder the socket to
the PCB, not the chip itself. This prevents overheating
the IC with the soldering iron and makes it easier to
switch a faulty one out.
●Stripping and twisting stranded wire
All wires in this kit are stranded (instead of solid core)
to bend more easily without fatigue. To make inserting
into PCB holes easier, twist the strands together
immediately after stripping off the plastic coating.
Connecting wires
The boards and enclosure-mounted components connect
together with the included hook-up wire and ribbon cable.
Use a ruler and wire cutters to cut the bulk collection of wire
down to the required individual lengths.
* denotes measurements for the OKAY 2.
Description
Connecting points
Length / type
Octave
selection
555_4040 output pins to
rotary switch and back
to 386 input
8” rainbow with 7
conductors
Power
S1 on bus PCB to switch
on back of volume pot
6” twisted 2-wire
LED
Bus PCB slot to LED on
volume label
8” (or 6” *) twisted
2-wire
Speaker
Speaker header on 386
to speaker
6” (or 8” *) twisted
2-wire
Volume
VOL header on 386 to
volume pot
7” rainbow with 3
conductors
386 power
386 power header from
bus slot
3” twisted 2-wire
555_4040
power
555_4040 power header
from bus slot
4” (or 9” *) twisted
2-wire
Keybed
555_4040 R2 and
SPST_VR right A#,B
6” twisted 2-wire
Wiring diagram
386 0.1.1
This board uses an LM386 chip to make a very simple
amplifier.
Name
Value
Explanation
C1
10uF
capacitor
Used for distortion.
Should be
omitted for the OKAY.
C2
.1uF (104)
Bypass capacitor
C3
220uF
For speaker amplification
C4
47nF (473)
C4 and R1 create a “snubber circuit”
to suppress self-oscillation noise
R1
10 (brown
black
black)
Part of snubber
POW
Power
Connects to bus PCB
INP
Audio input
The + pin will connect to the rotary
switch. The - pin can be omitted for
the OKAY because all boards share
the same ground.
DIST
Distortion
switch
Should be omitted for the OKAY.
VR1 /
VOL
Volume
potentiom
eter
VR1 and and the VOL header
redundantly expose the same three
points used to control the audio
volume before it gets amplified.
The configuration for VR1 is for an
on-board trimming potentiometer.
The okay’s volume potentiometer is
off-board, so VR1 can go unused.
To determine polarity, view the
potentiometer from the top with its
shaft pointed at you and the leads
pointing down. The left pot lead will
connect to the left VOL header pad,
labeled as ground. The other two
connect in order; middle to middle
and right to right.
SPK
Speaker
Connects to speaker or output jack.
The pin touching ground is labelled as
negative; the other is positive.
IC1
LM386
Amp IC chip, in socket
Wiring the ¼” jack (for OKAY 2 only)
The 386 PCB has one SPK output, and the jack is wired
between it and the actual speaker. Note that the jack’s
ground pin is connected to both the PCB’s and speaker’s
ground.
This jack has a switch in it, so the audio goes to the jack
only when something is plugged in but otherwise to the
speaker. Cool, huh?
The switch is mechanically simple but can sometimes
break in transit. Luckily, fixing it is also simple. There are
two extending contact limbs, and they should touch by
default and not touch when the something is inserted. If
that’s not the case, gently bend into the correct position.
Experiments to try:
●Try a higher value capacitor for C3 for a beefier sound
●Connect the input to a different sound source like
another small instrument or your phone
●Put a 10uF capacitor in C1 and connect the DIST
headers to a toggle switch. Instant fuzz distortion!
●If you have one, try connecting to a different speaker.
The 386 is low power, so there’s no real risk of
damage.
●The included potentiometer is linear but would actually
be better if it were logarithmic, due to the way humans
interpret volume. Luckily, it’s easy to to approximate a
logarithmic response by connecting the ground and
output pins (left and middle, when viewed from the
top) with a smaller resistor. Further investigation is left
as an exercise for the reader. (Hint: google “fake log
pot”)
555_4040 0.1.1
The 555_4040 board uses two ICs:
1. LM555: timer wired as an astable mutlivabratory
(oscillator)
2. CD4040: ripple-carry binary counter/divider (frequency
divider)
The 555 (IC1) is the heart of the OKAY. It oscillates at a
frequency determined by R1, R2, and C1. Its output is piped to
the input of the 4040 (IC2), where it’s divided 12 times to
make 12 different octaves.
The 12 octaves are exposed on the right side of the board,
grouped in halves from 1-6 and 7-12. The raw output of the
555 (octave 0) is accessible by the unlabeled, single header
pin to the bottom right of IC1.
Name
Value
Explanation
C1
10nF (103)
Sets oscillator frequency on IC1
C2
10nF (103)
Ties “Control voltage” IC pin on IC1 to
stable power, minimizing spurious
noise
C3
.1uF (104)
Bypass capacitor for IC1
C4
.1uF (104)
Bypass capacitor for IC2
R1
1k (brown
black red)
Sets oscillator frequency
R2
N/A
This connects to SPST_VR PCB
IC1
LM555
Timer IC chip, in socket
This manual suits for next models
1
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