Thonk AT-AT-AT User manual

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October 7th 2012 www.thonk.co.uk 1
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
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OVERVIEW
For the most recent version of this
document please visit www.thonk.co.uk
For all technical support please visit
http://bit.ly/R0nqyt on Muffwiggler.
The Thonk AT-AT-AT Triple Passive
Attenuator is a simple module comprised
of three identical and separate
attenuators. It requires no connection
behind the panel to your Eurorack power
supply.
The simplest description of an attenuator
is a ʻvolume knobʼ; you can use an
attenuator to control the volume of an
oscillator before it is fed to a filter for
example. Or, you might use an attenuator
to control the depth of LFO modulation
patched to filter cutoff CV.
On a modular synthesizer, attenuators are an important building block in
pretty much every part of your patch for both CV and audio duties.
Each attenuator has an input jack, a linear potentiometer to control
attenuation amount and an output jack. The AT-AT-AT is not a mixer.
DIY INSTRUCTIONS
This document gives detailed instructions which assume you have purchased
a complete kit from www.thonk.co.uk. It also assumes no previous knowledge
of electronics. To learn to solder try http://youtu.be/I_NU2ruzyc4
All individual components used can be purchased from www.Mouser.com, for
specific details see the Bill Of Materials (BOM) overleaf.
TOOLS REQUIRED
Soldering iron, pliers, wire strippers, small flat head screwdriver.
For this kit you can substitute scissors for wire strippers if you are careful. You
are likely to blunt the scissors if you donʼt take care however.

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October 7th 2012 www.thonk.co.uk 2
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
BILL OF MATERIALS
# inclʼ
Description
Info
1
Thonk AT-AT-AT Aluminium Panel
3
50K Linear Potentiometers (Solder Lug)
P160KNP-0QC15B50K
3
Black ʻDavies 1900hʼclone knobs
3
Plastic Washers
Fit behind panel
3
M7 Metal Washers
Fit on front panel
3
M7 Nuts
Fit on front panel
6
3.5mm Jack sockets (Kobiconn)
16PJ138
Hookup Wire
Var. colours, solid core or stranded
Tinned Copper Wire
26 SWG
Solder
Contains lead – wash hands before eating
18SWG 60/40
I have provided approx 50% more wire than you should require for a single
build. However, do take care to use it efficiently.
PJ-301BM jacks, known also as ʻFlight of Harmonyʼor ʻErthenvarʼjacks will
also fit this panel. Note that the solder pins have a different configuration.
Also, any pot rated 47k-100k will work fine as a direct substitute. You could
choose to replace with ʻAudioʼtaper pots.
Panel
Pots
Knobs
Plastic
Washers
Jacks x6
Screws
Metal
Washers Nuts
Hookup
Wire
Tinned
Wire
Solder
Warning :Solder
contains Lead

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October 7th 2012 www.thonk.co.uk 3
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
WIRING DIAGRAM
If you donʼt understand this, DONʼTPANIC
Continue onto page 4 for beginner friendly instructions.
VIEW FROM REAR OF PANEL
Ground
Attenuator 1
Attenuator 2
Attenuator 3
Ground
Tip
Switch
(not used)

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October 7th 2012 www.thonk.co.uk 4
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
BUILD INSTRUCTIONS
TIP – Start by emptying the zip-lock bag into a bowl. This makes it much
easier to pick parts as you need them. Keep the zip-lock bag handy for later.
1 - First you need to install the bottom two
jacks as shown. Make sure that the ground
pins which stick out the side of the jacks are
pointing up towards the top of the panel.
Be careful not to scratch the panel when
tightening the nuts. Putting insulation or
masking tape on the end of the pliers can
help stop any scratching.
Ground Pins pointing towards top of panel
2 – Next, take the Tinned Copper Wire and
use pliers to bend one end into a little hook
3 – For this section of the build, rotate the
panel so the jacks are at the top.
Take the hooked end of the Tinned Wire,
secure it in the ground pin indicated and
solder (do not cut the wire yet).
Solder
Ground

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October 7th 2012 www.thonk.co.uk 5
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
4 - Snip the other end of the wire so it is
approx 5mm longer than the distance to the
other ground pin, thread it through the loop
and solder.
5 – Now hook another piece of tinned wire
(do not cut it yet), but hook it onto the centre
of the piece you soldered.
Take care to position this accurately in the
centre (see step 6, this will need to fit
inbetween the next two jacks inserted)
Solder this second wire in place.
6 – Now fit the next two jack sockets, again
ensuring the ground pins are pointing
towards the top of the panel.
Youʼll need to bend the ground pins of the
first two jacks upwards so they are flush
against the plastic body of the jack.
The central piece of tinned wire should fit in
the gap between the new jacks.
Ground pins facing top of Panel
Solder
Solder

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October 7th 2012 www.thonk.co.uk 6
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
7 – Repeat steps 3 & 4 for the newly
installed jacks - Solder a small section of
tinned wire between the two ground pins.
8 – And again solder the middle section of
wire to the wire bridging the ground pins.
9 – Insert the final two jacks and repeat the
same steps as previously.
Install a bridging section of wire between the
two ground pins, and solder to the middle
section of wire.
All 6 ground pins on your jacks are now
connected together by the tinned wire.
Solder
Solder
Solder

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October 7th 2012 www.thonk.co.uk 7
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
10 - Double check visually that all 6 ground
pins on your jacks are now connected
together. You could save yourself a lot of
hassle later by double checking this now.
If you look in the gaps between the jacks
you should be able to see 9 solder joints.
There should be no connections yet to the
two jack pins which point directly away from
the panel.
Note: itʼs fine for the tinned wire to touch the
front panel, the panel is most likely already
grounded through the physical conection
with the jacks (and later the pots too).
11 – Solder one end of the tinned wire to the
left hand ground pin as shown, do not cut
the wire to length just yet. Youʼre going to
leave that wire hanging for now.
You can put the panel to one side now as
itʼs time to prepare the pots.
12 – First you need to remove and KEEP
the little rectangular tab.
They snap off very easily with a pair of
pliers.
They are pretty tiny so take care with them. I
suggest putting them in the zip-lock bag you
emptied as you go.
Why are you keeping them? Itʼs an old synth
DIY trick.
1
2
3
4
5
6
7
9
8
9 solder joints.
Count them.
Solder
Remove
Keep!

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October 7th 2012 www.thonk.co.uk 8
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
13 – Youʼre going to push those tiny
rectangular tabs into the split in each pot
shaft.
This makes the top of the pot shaft flare
open slightly. When we finish the module by
mounting the knobs youʼll find this gives a
much more snug fit. No wobbly knobs here.
Grip the tag halfway with pliers and insert
into the split end of the pot.
Use a screwdriver to push the tab about half
way down the ʻtoothedʼsection of the shaft
as indicated by the arrow in the second
picture.
Donʼt push it further than this as you WILL
snap the shaft if you push the tag right to the
bottom of the split.
14 – The plastic washers fit between the pot
and the rear of the panel.
They are not a tight fit over the pot shaft but
centralise themselves when the pots are
fastened to the panel.
The plastic washers shorten the length of
the shaft on the front side of the panel giving
a neater looking appearance when you fit
the knobs.
Fix the pots using the metal washer and nut
on the front of the panel.
Make sure the solder lugs are pointing
towards the jacks as shown in the photo.
Again, take care when tightening the nut that
you donʼtscratch the panel.
Plastic Washer
Jacks are off screen this way…

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October 7th 2012 www.thonk.co.uk 9
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
15 – Now you need to solder that wire you
still have hanging off the side.
16 – Letʼs move onto the hookup wire. This
is what you will use to make the connections
between the pots and jacks.
This wire has plastic shielding as you need
to avoid short circuits. This just means the
stripped ends of the wire shouldnʼt touch
anything other than the terminals on the pot
and jack that I show you to solder
With a passive circuit you are not likely to
cause any damage to anything by wiring
incorrectly or sloppily – it just wonʼt work.
You will have wire in at least two colours.
Rotate the Panel so the pots
are at the top.
Youʼre going to solder one
continuous piece of wire onto
the right hand terminal of each
pot.
Donʼt worry about the bare wire touching the
metal enclosure of the pot or the front panel
- as long as it doesnʼt touch the other
terminals of the pots you are fine.
Now all the jacks and pots share a ground
connection. Youʼre ready to move onto the
final step and complete the work on the
back of the panel.
By this point youʼve probably realised that
you could have achieved this grounding task
with a single piece of unbroken tinned wire.
After trying both ways I decided they were
both equally challenging. The one I chose
was much less ambiguous to describe
visually in this document
Solder
Solder
Solder

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October 7th 2012 www.thonk.co.uk 10
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
17 – There are two types of wire supplied in
the kits, solid core or stranded. Both types
work equally well for all applications on this
module.
Strip about 5-10mm of the insulation off one
end of each piece of wire to check which
type you have (donʼt cut the wire into pieces
yet).
If you are careful you can strip the plastic
shielding with scissors or a scalpel, but wire
strippers are best.
If you do have stranded wire, twist the
strands together between you thumb and
forefinger and ʻtinʼthe end. Tinning is
applying a small amount of solder to keep
the strands together.
18 – Take one of the stripped ends of your
wire and use pliers or your fingers to bend it
into a hook like so.
Solid Core
Stranded
Twist and Tin
TIP - If you move on from this kit to more complex projects where you
wire from a PCB to a front panel then I advise using stranded wire as it is
more strain resistant. For jobs like the AT-AT-AT where everything is
panel mounted, solid core is fine and slightly quicker to work with.

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October 7th 2012 www.thonk.co.uk 11
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
19 – Attach the hook to the middle terminal
of the Pot no 3 and solder.
20 – Now extend the wire out to the Jack terminal marked A.
Cut the wire so it is around 10mm longer than the distance to A, then hold
the wire gently to terminal A (without bending the pot terminal) and strip the
insulation off from this point. You can now pass the bare wire through the
hole in Terminal A, bend it round to secure and solder. You can cut off any
excess wire after soldering.
The wire should not be tight between the two points
, it shouldnʼt be bending
the terminals on either the pot or the jack. If anything it should bulge away
so it is a little malleable and you can rearrange its position once soldered.
Solder
Strip wire and
solder here
A

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October 7th 2012 www.thonk.co.uk 12
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
21 – You are now going to repeat exactly
the same process and solder from the
remaining empty terminal on Pot 3 to the
other bottom row jack as indicated below.
Solder
Solder
Congratulations. Attenuator 3 is now complete. This would be a good
moment to test your work. Mount the panel temporarily in your case to
see if attenuator 3 is working. You donʼt need a knob to try this out
quickly. Turn the pot fully off/counter-clockwise first.
Try patching an oscillator or sound source to AT-AT-AT ʻIn 3ʼ, and patch
from AT-AT-AT ʻOut 3ʼto your speaker or headphone amp. Pot 3 should
now be working as a volume control.
22 – So to finish the final two attenuators, 1 + 2, you just repeat the same
wiring job another two times. The photos below are reference for what a
complete module should roughly look like.
I do strongly advise following the wiring diagram on page 3 rather than
relying solely on these photos.!

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October 7th 2012 www.thonk.co.uk 13
AT-AT-AT – Triple
Passive Attenuator
Eurorack DIY Kit Instructions
Version 1.0
23 – The final task is fitting the knobs.
Turn all the pots fully counter-clockwise or
fully OFF.
Make sure the set-screw in the knob is
loosened just enough to allow the pot to fit
fully over the shaft of the pot. Be careful to
not loosen the screw so much it falls out.
Once fitted, the bottom of the knob should
pretty much be touching the nut.
Make sure the knob is fully counter-
clockwise, line the knob pointer up with the
first mark on the scale, hold the knob firmly
in place with your thumb and tighten the set
screw with a screwdriver.
If you find the knob feels a little tight or
ʻgrindyʼ, loosen the set-screw and push
some paper or thin card between the base
of the knob and the nut. This will just lift the
knob away from the nut slightly. Tighten the
set-screw and test again.
Repeat for the other two knobs, screw into
your Eurorack case and you are…
FIN
For technical support please use http://bit.ly/R0nqyt on the Muffwiggler forum.