Make the APC

Making the APC

Being that there are a number of resources online about how to solder, I am not going to go over that here. This is a fairly straightforward kit that should be a great first time project. If you haven’t soldered before I suggest you check out this page for a ton of examples and links. It’s actually how I learned to solder, by reading, watching, and then practicing. If this really is your first time, pick up some broken electronic part, and de-solder and re-solder parts to it till you have nice looking solder joints.

Document Map:

Step 1: The Parts
Step 2: Fitting the Case
Step 3: Soldering the 556
Step 4: Soldering the resistors and capacitors.
Step 5: The Speaker
Step 6: The Potentiometers
Step 7: Power
Step 8: The Case, and the headphone jack
Step 9: Finishing, and attaching the knobs


What you will need to build this kit:

  • Soldering Iron (a cheap one will work, but a temperature controlled iron will improve your life)
  • Shear Cutters
  • Solder
  • Wire strippers
  • Needle nose pliers
  • A small flat head screwdriver
  • A drill or��rotary tool like a Dremel along with various bits (depending on your case)
  • A marker
  • A fun case to put your kit in
  • A 9V Battery

Things you really should have, but do not absolutely need:

  • Helping hands
  • De-soldering braid
  • Multimeter
  • Tapered hand reamer
  • Small files

I suggest you check out this list of recommended items for a good soldering setup.

Some tips before we start:

  • Lay out everything beforehand, and go through the directions at least once before you start.
  • Keep your iron tip clean. I Highly recommend a brass tip cleaner.
  • Use 60/40 flux core lead solder, unless you have a good iron and know what you are doing.
  • The joints should look like a “Hershey’s Kiss”, completely covering the pad.
  • Do not over-heat things. It will only take 1-3 seconds at the most to solder a joint.
  • Don’t abuse your tools. Use your tools for their intended purpose, and keep them maintained. This will dramatically improve the quality of anything you do.
  • Double-check your work.
  • If you get stuck, don’t be afraid to ask questions.

Step 1: The Parts

Check your kit and make sure you have all the parts and tools you need. Since the speaker has a magnet, sometimes parts like to stick to it, so you should remove it from the plastic and check. Click on the image for details:


The parts include:

  • PCB
  • 556 Timer
  • Two 500K Pots
  • 1K R
  • 10K R
  • 4K7 R
  • .01uF Cap
  • .1uF Cap
  • 10uF Cap
  • 3.5mm Mono Jack
  • Speaker
  • Two Knobs
  • Switch
  • Button
  • 9v Strap
  • 1′ Wire – Black
  • 1′ Wire – Red

Step 2: Fitting the Case

I’ve placed this first, because this is what you are going to be providing for your kit. It’s also extremely important to have a sense of what you are going for prior to starting. This is a very important step. Time spent here thinking and measuring will save you a bunch of time and frustration later. Go ahead and get a sense of the size of your case. Place components around inside of it to see how well they fit. The 9V battery takes up nearly as much space as all of the other parts. Make sure you can fit everything comfortably inside of the case before you start.

I’ve designed this to fit all of the parts easily inside of a standard Altoids (or similar) tin. That includes all of the parts in this kit, as well as the battery. There is not a ton of space in there, so you need to be careful. You can’t really fit anything on top of the 9V battery, and you have to have your parts far enough away from the edges that they do not hit when closing the case. Try and get a good sense of how things fit before starting. Here are some examples:


You are also going to want to think about where you want your controls on the case, and how you might want to use them. Also try to use wire sparingly, as you will have to fit that in the case as well. You want enough to reach the part, and to have a bit of slack, but too much will give you problems when you try to close the case. The two feet provided should be more than enough for a standard Altoids tin, with extra to spare. Also in general, having a spare case may also be good in case you find that parts aren’t fitting as well as you had hoped. You should also go and check out the hacks page for some additional ideas.

Step 3: Soldering the 556


The 556 is the heart of the APC. It is extremely important that this is placed in the PCB properly, otherwise it will not work. You will notice that the silkscreen on the PCB has a notch in it. That corresponds to the notch in the 556. If the chip does not slide in easily, you can very carefully bend the leads against a flat surface till they are more parallel.


Once the chip is in, and you have verified that it is in correctly, you can simply bend the corner leads down to hold it in place while you solder.


Go ahead and start soldering it in place. Your soldered joints should hopefully look something like this:

Make sure there are no bridged solder joints, and solder fills the whole pad.

Step 4: Soldering the resistors and capacitors.

We will be doing the ceramic capacitors first. They are the two smaller yellow ones. These are actually different values. If you look carefully you can see a “103” and a “104” printed on them. Those correspond to the silkscreen on the PCB. Place the caps in their corresponding place (they can be placed in either orientation), and gently bend the leads out to hold them into place:

Go ahead and solder them into place. Then clip the leads just above the solder. It’s generally a good idea to not cut too deeply into the solder, as you can sometimes rip a pad off of a PCB.

The resistors will be next. You will have three of them, and each is of a different value:
1K, 4.7K, 10K

The colors on the resistor are going to be what tells you the value. They are read with the metallic��band on the right side. The first band is the ten’s place, the second is the one’s place, and the third is the multiplier. You can look up resistor color codes online for further information. For this kit you only need to deal with these three values. There is a photo reference below.

1K – Brown, Black, Red
4.7K – Yellow, Purple, Red
10k – Brown, Black, Orange

Place them in their corresponding places on the PCB by gently bending the leads to be parallel with each other. Like the smaller capacitors, the orientation does not matter.

Once they are in place, gently bend the leads outward to hold them in place, and then solder and clip them. Your PCB should now look something like this:

The final electronic component is the electrolytic capacitor. I’ve saved this for last as it is the only other component part that has polarity and needs to be placed in a specific orientation. This is also where thinking about the case you want to place your kit into is going to be helpful. The negative side of the capacitor is marked as negative. The leads can also tell you what polarity the component is, as the shorter is also negative.

There are three basic orientations you can use:



Pushed over (what I usually use)

How much space you have in your case, and where you are going to place the PCB will determine which orientation will be better for you. Flat is best if you are going to try and cram it into a flatter space, and vertical is good for cases where you are not going to stack parts on the PCB. Pushed over is great if you are going to be soldering the potentiometers to the PCB.

Step 5: The Speaker

You will only need to do this step if you want an internal speaker. I sometimes skip this if I know the APC will only be used for line out, or if the case cannot fit the speaker. If you have the space, I would recommend using the speaker. The headphone jack will wait till you are ready to case the APC, as it comes in from the outside, and will have to be mounted to the case prior to soldering onto the PCB.

First place a bit of solder on each of the pads of the speaker, this will help with attaching the wire:

Now strip just enough wire to attach to the speaker. You want to remove only enough to do the job. The speaker does not have any kind of polarity, so you do not have to worry about that. I like to use both the red and black wire only because it looks cooler when twisted (more about this below).

Apply heat to the solder blob and attach the wire. By applying a bit of heat to the wire, it should naturally pull some of the solder on. Once you remove the iron tip, let the blob cool before letting go of the wire. Once solidified, you should be able to gently pull on the wire without it detaching:

Now do the same for the other wire:

This is completely optional, but I like to then twist the wire gently to provide a cool effect. This does nothing other than look nice. It adds a bit of structural support, but that is fairly unimportant. You only want to use enough wire for the job though. You’ll only need a couple inches at most, but measure inside of your case to be sure, then clip the wires to fit:

Now you’ll want to attach the speaker to the PCB where it is marked “Speaker”. Strip just enough wire to fit through the PCB for both wires. The orientation does not matter, but it can be helpful to use black for negative and red for positive to have a consistent look. While the speaker does not have polarity, the output jack does, which is right next to the speaker on the PCB.

Go ahead and solder them into place, bending the wires on the back of the PCB may help to hold it in place.

Step 6: The Potentiometers

The PCB is designed for either on-board pots, or off-board. Structurally, placing the pots onto the PCB gives a nice solid feel once they are in the case. However, make sure you have space in the case you are going to be using. Of the three contacts, only two are the ones that will determine the resistance change. In both cases that is the outer two, which have “500K” written between them. This was done because it allowed the board to be mostly single sided. That means that if you want both of your knobs to go up in frequency in a clockwise direction, you will need to offset the right pot by one space.

There are also some small tabs on the tops of the pots. They are used to grip into a case and hold it into a specific place. They are not very useful unless you are good at creating small vertical slits in the case. My suggestion is to just bend them downward:

On-Board soldering:

If you want to attach the pots directly to the PCB, you’ll first want to go ahead and fill each of the pads on the PCB with solder:

Then straighten out the leads of the pots if they are bent:

Now add solder to the leads on the pots:

Now center the pot over the three holes, and heat the middle one. Allow it to sink down and then solidify before you let go. This joint does not have to be perfect, as you will be re-touching it later:

Heat the other two points, adding a bit of solder. You want enough to fully cover them and make a solid connection:

Now re-touch the middle one, adding a bit of solder. It should now look something like this:

You can go ahead and do the right pot in a similar way. If you are off-setting the right one, yours should look like this:

Without the off-set:

Off-Board Soldering:

Depending on how you want the knobs to behave, you have a choice of which two points you want to solder the wires to. Increasing while turning clockwise is the common and intuitive way, but you may want to swap that depending on the case:

Increases as turned clockwiseAPC KIT 47
Decreases as turned clockwise

I like to go ahead and add solder to the pots first. Then strip just enough of the wires to make a solid connection. Now, apply heat to the joint and insert the wire, applying heat to the wire as well:

Do the other wire now, and it should look something like this:

I once again like to add a bit of a twist for decorative purposes. You will only want to use enough wire to get from the PCB to where the pot is going to be. Now clip and strip the other side of the wires to fit, but leave a little slack:

You will now solder the wires to the outside two pads on the PCB, or you can solder to the “touch” connection points. It does not matter which way you solder them in, as there is no polarity for these parts. The “touch” points can be used for bringing out additional resistance based controls (like touch contacts or photo resistors). Your APC should now look something like this:

Step 7: Power

You have now mostly completed the soldering portion of the APC, and we can now test it. You can do that by connecting the 9V battery. The red wire is + and the black wire is -. First you should pick either positive or negative, and solder that to the PCB. The other one you will keep detached for now, and simply touch that to the PCB, holding it in place.

It should hopefully be making some noise. If not, try turning the pots to the middle, as the APC may be stuck in a spot that is too high to hear. If you still hear nothing, make sure nothing is shorting, and that you are connected to the correct place on the PCB for power. Look for any possible shorts, solder blobs, hanging leads, etc. If you still can’t get it to make sound, then consult the troubleshooting section.

Now that you’ve tested the kit and it’s working, it is time to decide how you want to control the power. The kit comes with both a button and a switch. The button is used for momentary presses, and is useful if you want to play actual melodies with the instrument. I suggest at least using the button. The other option is the switch, which will cause the APC to be on continuously. This is useful if you want a continuous tone. You can also use them both to provide either option. I will be going over all of the options, but it is up to you to decide what you want.

Individually wired
Both the button and the switch will be wired fairly similarly if you want to use either by itself. If you just want one, I would suggest using the button, as it provides much more control. The switch is useful if you want the APC to be able to stay on and generate a tone. You will simply solder the loose wire from the 9V to one of the leads of the button, or the center of the switch:


Now you will strip and solder a wire from the other point of the button, or either of the side leads from the switch. Finally, you will solder the other end to the PCB, completing the circuit:
APC KIT 55 Now when you press the button (or flip the switch, if you used the switch) you should hear some sound.

Using both the button and the switch
If you want to use both, you will need to solder them in parallel. That way, if either the button or the switch is used, the instrument will come on. It takes a bit of extra time, but is worth the effort if you want both controls.����You are going to solder the loose wire of the 9v to one lead of the button. Then strip and solder another wire from that same lead on the button where the battery connects to one of the side leads on the switch. Then strip and solder a length of wire from the PCB to the center of the switch. Now, strip and solder a wire from the center of the switch to the empty lead of the button. You should end up with something like this (click to enlarge):


Hopefully, when either the button or the switch is used, you will start to hear sound.

Step 8: The Case, and the headphone jack.

This step will more than likely take more time than the rest of the project so far. The time you spend here will depend on how much room there is in the case you have selected, and how nice you want things to look. Being careful will take more time, but you will end up with something nicer. Since I cannot possibly guess at the different varieties of cases that people will choose, I am just going to go over some best practices, and largely leave the decisions up to the maker. Also, this is where you will add in the headphone jack, if that is something you are interested in having. Check out the hacks page for some ideas, as you may want to revise your plans before things become permanent.

Hopefully you have already tried to fit everything into the case, and have at least a good idea of where you want things to go. When I said at the beginning that the planning stage for this was the most important, I meant that. You will now have to go about making sure once again that things fit in roughly how you had already planned.  Now is a good time to make revisions to your plan if needed, as once things start soldering together, the shape changes a bit. If enough room wasn’t allowed, then you may have to move something from your original planned position.

The way I fit pieces is both from the inside, and the outside. I take the nut and washer off of the part, and try that from the outside, keeping in mind how much space is going to be used inside. This takes a bit of spatial thinking, and any extra time spent here is well worth it. Make sure you have a solid idea before you mark or drill. Once I have a good idea of where I want things to be, I close up the case, and then use the nuts and washer to mark the holes on the case. I then use the marker and place a small dot in the center:

A useful thing I’ve found for Altoids tins is to stay within the inner border of the tin. That generally keeps parts free of the lip on the inside of the lid.��When marking on the sides of the case, make sure that the lid is already closed, as holes in the center of the tin will actually prevent the case from closing properly:

Now that you’ve marked the case, and you are fairly confident that your parts will fit in the configuration you’ve selected, it’s time to drill. I personally use a Dremel with a 1/8″ bit, and a tapered hand reamer for all holes in all cases I use. The tapered hand reamer allows you to create holes to size, and very specifically fit your parts into the case. If you do not have a tapered hand reamer, then you will need an assortment of drill bits to be able to drill out the properly sized holes. Regardless, I suggest starting off with a smaller bit first. A smaller bit is easier to control, and you’ll have an easier time centering it. Once you have a starter hole, you can then move onto a larger bit, or the tapered hand reamer.

My tapered hand reamer is my absolute favorite tool.APC KIT 60 You should get one if you like to make nice round holes in things.

Just to show how nice the hand reamer works, the hole on the left is an untouched hole from the reamer. The one on the right I used two drill bits, and some files to straighten the case back out:

To further put this into perspective, this is a side view of the case. The side holes I drilled with the drill bits, and the case became a little warped. I was able to push it back into shape (something that also happens somewhat naturally when you start tightening down the parts). However, much more work was needed with my files and some pliers. You can see the perfectly round hole on the top of the tin, without any distortion of the case.

Please keep in mind that this is the most dangerous part of the whole project, and you should be careful when drilling. Don’t do anything like drilling down towards your leg, or holding the tin in your hand while making the hole. Firmly clamp or hold the case against a solid surface, move slowly, and be careful. Also, keep in mind that the thicker and harder the case, the more dangerous it will be. If you are using a solid case, then make sure to clamp it down before you even try to drill it. There is no reason for you to get hurt if you are cautious and think before you drill. Nobody has ever been hurt in one of my workshops, but I wouldn’t want someone to hurt themselves at home doing this either.

With the reamer
Since this is a bit easier, I’ll cover this style first. You’ll want to go ahead and drill all of your starter holes. I prefer a Dremel because it gives better control, but a drill will work too. Then once those are drilled, you are going to use the reamer to open the hole up more. By applying a rotational movement back and forth while gently pushing inward, it shaves away bits of the case, and the hole will get larger. You will want to fit your part into the hole at many points during this. Fit early, fit often. The part should easily slide into the hole, and not get caught, but the hole should be far smaller than both the washer and nut for a tight fit.

APC KIT 59If you are going to put your pots here, move them down further. Otherwise they will brush against the lip on the inside. This also leaves little room for the speaker inside, so I wouldn’t suggest it if you want to use one.

APC KIT 60APC KIT 61The one on the left was done with the reamer. The one on the right is from a drill bit.

Continue to do this with all of the holes till all of the parts fit in their respective holes.  If you are unsure about the size, then keep fitting the part. It’s better to do this too many times than to over-size your hole where the part just falls through.

With just drill bits
You will want to go ahead and drill all of your starter holes with the smaller drill bit (I generally use 1/8″ as a starter). Like I said earlier, this makes the process much easier for centering the larger holes. Now you will need to find a drill bit for each of the parts. I’ve gone ahead and done that, but first I want to go over how I find the proper drill bit size. Basically I use the nut to size the bit, and place the nut over each drill bit. I keep trying larger drill bits till the nut no longer fits over, but the outside of the nut is still wider than the bit. This is generally a good way to find the size when you do not know what size to use.

However, I’ve gone ahead and done that. The potentiometers, button, and headphone jack will all be comfortable with a 5/16″, and the switch will work with a 7/32″. Once you have all the bits, go ahead and carefully drill out the holes. If the part does not easily go through, then use the next sized bit you have, as long as it is not larger than the size of the nut. Hopefully everything fits well, and you are done with drilling. You may want to use some pliers and small files to even out the edges if your case is tin. It tends to rip and warp a bit, but you can usually fix it easily enough.

The headphone jack
The final step is the headphone jack. You should have already drilled out the hole for it, and it fits in easily. You should have already pulled off the nut for sizing, but if you have not done that, then go ahead and do so now. For this jack the longer lead is going to be ground, which is going to go to the negative line connection on the PCB. You are going to strip and solder wires to the headphone jack, and then twist if you like:

You can then feed the wire and jack through the hole, run the nut up the jack, and attach it to the case. If you solder the wire to the board first, you will not be able to screw on the nut. Once the nut is screwed on, you then clip, strip, and solder the other side of the wire to the PCB.

At this point, you can now start attaching everything in your case, as you are mostly done.

Step 9: Finishing, and attaching the knobs


There are just a few things you may want to do to finish things up. I like to take files to all of the edges and make sure things are nice and bur free. I also clean out the case after drilling, so that all of the dust and bits are gone. If the case is metal (like the Altoids tin), I also like to make sure that nothing is going to short. I clip anything sharp, and cover anything in electrical tape if I’m worried about it. If it stops working when you close the case or move it, then you simply have a short. Hopefully the case closes well, but if not, you can usually move wires around till things fit at least a little better. If there is too much wire, you may need to desolder one of the sides and trim the wire before reconnecting it. You want enough wire to open the case, but not so much that it causes it to jam open.

You can now put the knobs on the pots. There is a small screw in the back of the knobs. You want to unscrew those enough so that they slide easily onto the pots. If they do not go on easily, then just unscrew them a bit. It’s a tight fit, even a small overlap will cause it to be difficult to put on. Then simply tighten the screw, and you should hopefully be done.

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