How to wire up a Stomp Box / Effects Pedal

Today we're going to talk about how to wire up a stompbox.

Apart from the effects circuit itself, there are three things that have to be thought about when wiring up a stompbox, which are the stomp switch, the stereo input jack and the DC-in connector.

I’ll be referring to this image throughout the explanation (as with all images on here, click to enlarge):

1. The Switch

To try to make this easy to follow, consider the left-hand column of the switch to be the input column, the middle column to be the LED column, and the right-hand column to be the output column. If for any reason you only have a 6-pin switch, you can still use it, just without the LED column.


Off position

In the OFF position, pin 4 is connected to pin 7, pin 5 is connected to pin 8, and pin 6 is connected to pin 9 (in my diagram at least – you may have a switch with different numbers written on it, though often they have none at all).

Looking at just the left and right columns, the input comes in from the input jack via the yellow wire connected to pin 4, is directed downwards to pin 7, which is shorted to pin 9 via the jumper wire, then this is redirected up to pin 6 which is connected to the output jack. In other words, a bypass is in operation. As the effects circuit itself is completely disconnected, it cannot influence the signal, so this is true bypass.

As for the middle column, there is not much going on there. The ground/earth wire is connected to pin 5, but it is not redirected anywhere, so nothing happens, and the LED does not light up.

On position

In the ON position, pin 4 is connected to pin 1, pin 5 is connected to pin 2 and pin 6 is connected to pin 3.

Again, looking at just the left and right columns, the input again comes in from the input jack via the yellow wire connected to pin 4, is directed upwards to pin 1, which then goes to the input of the effects circuit. The output of the effects circuit goes to pin 3, and this is redirected down to pin 6 which is connected to the output jack.

As for the middle column, the ground/earth wire is connected to pin 5, which is redirected up to pin 2 and fed to the negative terminal of the LED, allowing it to light up.

OK, that’s the switch explained, but there’s more going on here.

2. The Stereo Input Jack

You may be wondering why a stereo input jack is required, when you are only using a mono signal. Well, that’s because the third connector (pin 3) on the input jack is used to control the power supply to the circuit.

Let’s assume for a moment that you are using a battery. Instead of the negative of the battery being connected straight to the negative of the effects circuit, which would mean the battery is in use ALWAYS (even when the circuit appears to be switched off), the negative of the battery is instead connected to the third connector (pin 3) of the stereo input jack. That way, when nothing is plugged into the stomp box, the third connector is not connected to anything and the battery is not being used. When you plug in a mono jack plug, it shorts the third connector to the shield/sleeve connector (pin 1) of the socket, which in turn connects it to earth/ground, powering the effects circuit.

You may wonder why you don’t just power up the battery at the same time as switching on the effects circuit. Without going into too many details, this is because the sudden surge of power leads to a loud popping noise, which no-one wants to hear.

3. The DC-in Connector

Lastly, we have the (5.5 x 2.1mm) DC-in connector. This also has three connectors and can sometimes cause confusion, since instead of having a positive inner (centre pin/tip), which would be the norm for most electronic items, it actually has a negative inner. I’ve numbered the pins in the diagram for clarity, as follows: pin 1 is the (negative) inner/pin/tip and is connected to the negative of the battery, pin 2 is the outer (sleeve) and is connected to the positive (+9v) of the effects circuit, and finally in a similar way to the stereo input jack, pin 3 is the 3rd, extra, pin and is connected to the positive terminal of the battery.

(The difference between this and the input jack is that in this case, pins 2 and 3 are normally shorted UNTIL you plug in a power supply, at which time pin 3 becomes disconnected.)

When nothing is plugged in, the positive terminal of the battery, which is connected to pin 3, is shorted to pin 2, and continues on its way to the positive of the effects circuit. When the power supply is plugged in, however, pin 3 (and therefore the positive of the battery) is disconnected, and the positive voltage from the power supply goes directly to the effects circuit via pin 2.

One more thing to note is that since the DC-in socket has a positive outer, it should be one with a plastic surround, so that the outer does not make electrical contact with the enclosure (which is grounded/earthed).

Something like this (below) is fine:

Whereas something like this (below) is NOT suitable:

   

Additional information

With thanks to CheopisIV (http://www.stuntmonkeypedals.com/) and bugg over at the mylespaul forums for clearing this up, it is a wise idea to ground the input of the circuit itself when not in use (in other words, while it is being bypassed). Without a grounded input, the input signal can float all over the place and by the time it gets amplified through the circuit, there can be quite a large uncontrolled signal in there. Now theoretically this wouldn't be connected to the output socket, since the circuit is being bypassed, but the noise can be picked up by other means, and so it is safer to just avoid it if possible. 

So we simply add one extra jumper wire from the leg of the switch that goes to the circuit input and the unused leg on the LED column. The resulting wiring would look like so:

While the circuit is bypassed, the circuit input is connected to the ground wire going into the centre pin (pin 5) of the switch. When the switch is engaged, this connection is broken and the circuit just works as previously described.

Finally here are a couple more circuits for people who want to take out either the battery or the DC-in jack:

Under the stairs

I’m really behind on the updates, sorry. I’ve been doing some real-world stuff that didn’t leave much time for much DIY guitar-related fun. I am happy to report that one of the reasons I haven’t had as much time to tinker is that I’ve actually been playing the guitar a bit.

One of the things that took up some of my time was sorting out a new property back home, which required a rather long return flight, not helped by the fact that the airline forgot to load the headphones for the entertainment system on the way there, and I hadn’t brought my own for the first time ever.

While I was back home, I rifled through some stuff that I had left at a friend’s house and stumbled across a stomp box I made just after finishing the DIY Strat. I had totally forgotten about it, and even if I had remembered I would have been sure it had been thrown out.





Anyway, for the very few that may be interested, here it is. Note the professional enclosure (not)! What a great colour (grey primer covered by lacquer, which was all I had at the time).

The circuit is one of Aron Nelson’s designs (if you don’t know who Aron Nelson is, but are interested in DIY stomp boxes, then Google his name now). This particular circuit is “The Hornet” and the circuit diagram can be found here: http://www.diystompboxes.com/pedals/schematics.html (scroll down a bit to find it)

Unfortunately when I made this, I didn’t really understand how to do the switching, so I ended up wiring it up like this:



I mean, it works (sort of), but it’s not a good way to wire it up for a couple of reasons.
Firstly, this is why it works...

The switch has 4 legs. In one position, legs 1 and 2 are shorted. In the other position legs 3 and 4 are shorted.

When poles 1 and 2 are shorted, power is sent to the circuit.

When poles 3 and 4 are shorted, power is disconnected from the circuit, but the input is shorted to the output, creating a bypass.

However, here’s why it’s not a good way to wire it up...

1. Even when no power is applied, and a bypass is in operation, the circuit still manages to affect the sound, for example by creating some sort of a path from the signal to earth.

2. When the switch is pressed, the circuit is activated at the same time as power is applied, and a loud popping noise is heard.

For those that are interested, in the next blog post, I’ll show you the correct way to wire up a switch in a stomp box:

Making a nut for playing slide guitar

I recently mentioned to a friend of mine that I was thinking of making a new nut for my acoustic guitar, and he generously donated a couple of nut blanks. One is ebony and the other is Corian. I will use the ebony one to make the new standard nut (which will no doubt be covered in a future blog entry), but decided to make a raised nut with the Corian for when I want to play slide guitar.

Corian, incidentally, is a material that is most commonly used on the surfaces of kitchen units, but has also been used by both Gibson and Martin to make nuts. It is not the best material, tonally-speaking (though it’s hardly crap), but it is easy to work with. More info about Corian can be found here: http://en.wikipedia.org/wiki/Corian

One of the bonuses of a raised nut for playing slide guitar is that it will be flat, rather than radiused, so no need to work out exact curvature, etc., and since it will be raised off the fretboard, there is no need to worry about precise height measurements. That coupled with the fact that it is Corian should make this a pretty easy project.

My guitar neck is pretty thin (just how I like it). It measures a little under an inch and three quarters. One and eleven sixteenths would probably be more accurate. The nut for playing slide was going to be cut a little wider – something like one and seven eighths. It would stick out a little on each side, but this is OK.

First thing was to cut it roughly to shape. It was just a little too thick, but I would deal with that later. As for the length, well, I had to cut about three eighths of an inch off with a hacksaw. I didn’t feel the need to take a photo of this. Next was to file a curve onto the top, so that the strings fall away on the head side of the nut. Unfortunately my vice isn’t the best, so I needed to do the filing in the way that is pictured here, one half at a time. This method puts the nut at risk when you lean on it with the file, as it could easily snap in half, so be very careful if you do it this way, and support the back of the nut with your finger. If you have a better vice that can grip the full length of the nut while you work on it, then that’s a better solution.



As previously mentioned, the nut was just a little bit too thick, so I solved this by rubbing it on a piece of sandpaper, which was lying on a flat tile. This is a commonly-used and very effective solution. I also used the sandpaper to help finish rounding off the top curve a little bit too.



Here's the basic shape after the vice and sandpaper:



Next thing was to file the nut slots. This can be quite intimidating, but the secret is a good set of nut files and a bit of reading (of course practice makes perfect too). I highly recommend checking out http://www.frets.com for information on this type of thing.

I recently bought a set of nut files called “Norman Guitar Nut File System”. They’re made by a guy called Norman Trent and he mostly sells them on ebay. He has excellent feedback, but some Googling suggests that some people are not happy with how long the files stay sharp, or Norman’s customer support. All I can say is that I got my files pretty quick and they worked well on this project. Norman also supplies a handy laminated sheet to help you mark the correct position for the slots, as shown here.



Slot positions marked and ready to do some filing.



The next step was to actually cut the slots. The depth you cut down should be a little over half of the diameter of the string itself. Also, you should file down at an angle so that the slot follows the curve of the top of the nut. This is to make sure the string makes good contact at the very edge of the nut when it meets the fret board and therefore cut out any buzzing, or intonation problems.

After the final filing I gave the whole nut a once-over with very thin sandpaper, just to shine it up a bit. Here is the end result.



And now here’s the nut on the guitar. It sticks out a little bit at the sides, as planned, and also sits pretty high off the guitar. Now I can really attack that thing with a slide without worrying about banging into the frets.

Gibson Deluxe Tuners (part three - the fix)

Please note that this post is part three of four posts. I highly recommend reading all four posts in order before acting on any of the information.

The other parts are located here:

Part 1: http://diystrat.blogspot.com/2009/01/gibson-deluxe-tuners-and-why-they-suck.html
Part 2: http://diystrat.blogspot.com/2009/01/gibson-deluxe-tuners-part-two.html
Part 4: http://diystrat.blogspot.com/2010/01/gibson-deluxe-tuners-revisit.html

OK! Done!

I tried various different options and finally settled on one that I was very happy with. Ironically, it was the one I thought wouldn’t work – the solder fix.

I had already tried the glue repair in the past, but it eventually broke again, so I didn’t even bother trying this time. However, it was going to be my last-resort fix if necessary.

Before I show you the solder fix, I should mention that I did try the metal strap solution first. I cut out a little paper template to fit over the tuner and then went hunting for a suitable piece of metal.

(paper template)



I really wanted to find a nice little piece of brass, but I found a piece of scrap sprung steel that was just the right size, so I thought I’d try that.

(piece of metal before I bent it to shape)



However, when I tried to bend it to a 90-degree angle, it snapped. I tried again with a different piece of metal, but the same thing happened. It’s still a possible solution, but you would need to find metal that wasn’t so prone to snapping, or know how to properly heat-treat it.

So I ditched the metal strap idea and tried solder instead. I was pleasantly surprised to see that it stuck to the tuner casing EXTREMELY well. So well, in fact, that the test blob I tried on the inside first was a pain to file off.

I assembled the tuner and held the back cover in a vice, then heated the join with a soldering iron, as shown here.



Now here it is with some solder added.



The whole tuner (and vice) acts as a heat sink, so you need to have a powerful enough soldering iron to heat up the area around the join before all the heat gets sucked away (be careful that you don’t accidentally lean the soldering iron against the tuner button, by the way - I nearly did that a couple of times). I used a 40 watt soldering iron, but I’d recommend you use at least 60 watts, if not substantially more. I’d also recommend that you don’t touch the tuner button with your finger (or anything else) until the metal has cooled down again, just in case it has softened up at all. And since I’ve already mentioned waiting, just wait until the whole tuner has cooled down before you touch it. Mine got VERY hot. And don’t blow on the tuner to cool it down quicker either - this is bad for solder joints.

Finally, a clean up with a file and we're done!



The tuner is now back on the guitar and the fix is completely hidden. A very satisfactory result indeed.

EDIT: I've since found out that there is another (known) trick to repairing these tuners, which is to attach the back cover, turn the tuner over and hit the middle of each tab with a punch. This distorts the tab just enough to give it some grip. More information here: http://diystrat.blogspot.com/2010/01/gibson-deluxe-tuners-revisit.html.

Gibson Deluxe Tuners (part two)

Please note that this post is part two of four posts. I highly recommend reading all four posts in order before acting on any of the information.

The other parts are located here:

Part 1: http://diystrat.blogspot.com/2009/01/gibson-deluxe-tuners-and-why-they-suck.html
Part 3: http://diystrat.blogspot.com/2009/02/gibson-deluxe-tuners-fix.html
Part 4: http://diystrat.blogspot.com/2010/01/gibson-deluxe-tuners-revisit.html

Well, the Gibson Deluxe Tuners post certainly attracted some attention. Seems there are plenty of people out there with the same problem.

Before I talk about my repair options, I’d like to discuss a little further the design limitations of the Gibson Deluxe Tuners. I previously mentioned that the little tabs that attach the back cover to the main plate do not fold over once they go through the main plate, which I found strange. While exploring solutions over the past few days I noticed that a lot of replacement tuners from other (often cheaper) brands had tabs which DO fold over, keeping them very firmly attached to the main plate. I really do have to scratch my head at why the Gibson Deluxe Tuner designers decided not to do this.

Non-Gibson Deluxe Tuners with tabs that fold over:



Secondly, I have noticed that there is one more problem with these tuners, which is that the worm gear wobbles quite a bit, even when the tuner is working perfectly, with the back cover attached. It doesn’t wobble from side to side, but rather away from and towards the guitar head. I hope that makes sense. This is caused by the claws not gripping around the worm gear, but rather, just stopping it from moving from side to side. The alternative solution offered by the Gibson Deluxe Tuners is to make the cutouts on the back cover (which let the worm gear pass through the sides of it) limit the movement of the worm gear away from the guitar head. Unfortunately, these are quite imprecisely cut, so sometimes allow for far too much movement.

So given that second note, I have decided that I need to tackle the wobble problem before attaching the back cover, since once I attach it I don’t want to have to take it apart again.
What I will do is file a little bit off the bottom surface of the back cover (leaving the tabs intact), so as to move the cutouts closer to the worm gear and hold it in place better. This has the added benefit of effectively extending the length of the tabs (not enough to fold over, unfortunately, but maybe just enough for a little bit of extra purchase)
[Edit: In the end I found the reason for, and the solution to, the wobble problem, which I've documented at the end of part four. Please check it out before you start any work.]

So after a bit of thought, I figure I have maybe three realistic options:

1. Make a type of metal strap, which would hold the back cover on. It would be held down by the two screws that would hold the main plate to the guitar. The disadvantages of this are that the strap would be visible and the screws might need to be swapped for longer ones. The advantage would be that it would require no irreversible modification to the guitar or the tuner, and it might actually look quite cool.

2. Solder the back plate to the main plate. Advantages would be that it would be a quick and easy repair that should be quite strong and fairly reversible. Unfortunately I’m not convinced the metal used on the tuners would accept solder readily. Really, I should be looking at brazing, but unfortunately that's just not an option for me.

3. Similar to 2, but use glue, most likely 2-part epoxy. Quick and dirty solution, but may work well.

Whichever method I choose, I will still file a thin layer off the bottom first.

I’m off work all next week (for Chinese New Year), so I’ll decide what I want to do then.

Gibson Deluxe Tuners (a weak design?)

Please note that this post is part one of four posts. I highly recommend reading all four posts in order before acting on any of the information.

The other parts are located here:

Part 2: http://diystrat.blogspot.com/2009/01/gibson-deluxe-tuners-part-two.html
Part 3: http://diystrat.blogspot.com/2009/02/gibson-deluxe-tuners-fix.html
Part 4: http://diystrat.blogspot.com/2010/01/gibson-deluxe-tuners-revisit.html

I have a problem with one of the tuners on my Les Paul. It had the problem already when I bought the guitar a few years ago and I managed to do a temporary fix, but the problem has resurfaced.

Before you continue, please note that this is written from an engineering point of view.

Firstly, let’s have a look at a typical stamped (open-backed) guitar tuner.

There are several components and many names for those components, so my apologies if I use ones that you are not accustomed to. Firstly, the tuner can also be called the tuning head, tuning peg, or the machine head (and possibly other names). It has a main plate, through which the main cylinder (or capstan), passes. The capstan is the shaft that the string itself passes through. On the end of the capstan is a gear, sometimes called the pinion gear, and a screw/bolt holds that on to the end of the capstan. Then we have another shaft or pin with the tuner knob (or button) on the end of it. This pin has a gear on it too (in fact they are one part in most cases), and this particular gear is known as a worm gear. From now on I will just refer to this shaft as the worm gear.

As an aside, and for any non-engineer-minded people out there, the reason a worm gear is used is because turning the button/knob will rotate the worm gear, which will in turn rotate the pinion gear and the capstan, thus tightening or loosening the string, whereas no matter how much you tighten the string, the pinion gear cannot force the worm gear to turn. This is a really good way to keep strings in tune without making it really hard to turn the knob.

OK, back to the description of the tuner. There is one further feature that I have not yet mentioned and that is the retaining “claws” which are part of the main plate and hold the worm gear in place. The claws stop the worm gear from moving away from the pinion gear or falling away from the main plate. The plate stops the worm gear from falling against the guitar and the pinion gear stops it from falling out in the direction of the capstan. So hopefully you can see that the worm gear cannot possibly fall out unless the pinion gear is removed.

Now to the Gibson Deluxe Tuners (and why I think they are a weak design).

As you can see, the tuner has the same components as any standard open-backed tuner, but please note one subtle difference – although the claws stop the worm gear from moving away from, or towards the pinion gear (i.e. from side to side), they don't stop it from falling away from the main plate. Seriously, it can just fall right off.

“But wait!”, I hear you Gibson Deluxe Tuner fans shouting, “The Gibson Deluxe Tuners have a back cover which stops the worm gear from falling away from the main plate!”

Well, you are correct, but this leads me to the problem with my tuner... the back cover has fallen off. And this brings me to my second criticism of Gibson Deluxe Tuner design. You would think that, if the back cover was the only thing holding the worm gear in place, it would be held on in a way that would be very hard to move.
Let’s have a look at their design.

The back cover is held on with two little tabs (one of mine is slightly damaged, but this happened while I was trying to find a solution to keeping it in place. It originally fell off with the tabs intact). Now as an engineer, I would think that a tab should at least fold over to keep something in place, but these ones just go into slots and do not appear to be twisted, folded, or in any other way modified once they go through the slots. In other words they are held in by “interference fit” only, so that they can come out just as easily as they went in (edit: actually, this isn't 100% correct - they are "staked" in place [see the comments at the end of this post], although that doesn't add much strength in the direction they would fall off ). Now let’s think about what’s on the end of the worm gear. That’s right, a big knob/button that sticks out and is basically on the end of a lever. What do we often use levers for? Well, for prising things out of place for one. The longer the lever, the easier it is. So one accidental knock on the tuning knob and you can dislodge the back cover, letting the worm gear fall out of place.

In the course of trying to find a single replacement Gibson Deluxe Tuner (which, not surprisingly, cannot be bought separately), I have noticed many other people scrambling to buy single replacements off ebay or asking if anyone has a spare one on musicians’ forums. A full set is not cheap either; around £60 would not be unusual. I wouldn’t even mind paying that if I though it was a good strong design, but I think you can guess by my rantings how much I think of these things. Unfortunately replacing them with anything other than originals devalues the guitar, so there isn’t much choice.

Additionally, on the front face of the guitar head you need to use a bushing (also called a ferrule) which stops the capstan from rubbing on the wood of the guitar when it is being rotated, and whereas these are normally press-in bushings on tuners of similar design to Gibson Deluxe Tuners, on the actual Gibson ones, they are screw-in bushings. Now I have no complaints about this, design-wise, I’m just saying that there are very few replacements available other than the Gibson Deluxe Tuners.

Gibson Deluxe Tuner bushing (and washer)

Standard bushing

So stay tuned (no pun intended) for the next blog post, where I will try to fix mine.

The Chiquita Amp

You may think the name of this amp came about because of its size, but in fact it was simply because of what was printed on the wood used to make the box. You see, it was made with the thin wood from a Chiquita banana crate. Incidentally, this amp has no connection whatsoever to the wonderful Erlewine (and later Hondo) Chiquita travel guitar, as featured on Back to the Future, or the little amplifier that was sometimes included with it. In fact I didn't even know about that model name until years after I made this. Apologies for any confusion.

After finishing the DIY Strat, I decided I needed a little amp. I had next to no money to actually buy one, so I thought I might as well just make one. After a bit of research online, I settled on a simple audio amp using a TDA2030A. Let me just state right now that this was back in 2000, so the amount of information available online at the time was much more limited. I’m sure there are plenty of really good circuits available for fantastic mini guitar amplifiers these days.

Anyway, at the time I wanted to build something that was VERY portable and could run off a power adapter for a stomp box. This fitted the bill.

The circuit was just copied straight from one of the specifications documents for the TDA2030A, which are available on many sites such as the following: http://www.unisonic.com.tw/datasheet/TDA2030A.pdf

There are several circuits suggested, and I can't find the exact schematic on any sheets right now, so I've redrawn the one I did below (click on the image for a larger version):

As you can see from the finished veroboard circuit, it is a very simple design. The TDA2030A is at a distance from the board as I wanted to bolt it onto a small heat sink to help dissipate some of the heat. As I said, it can run off 9 volts, but the good thing about the TDA2030A is that you can easily bump the input voltage up to something like 18v and get much more power out of it.

The box was glued together, except for the back, which was bolted on. This way I could open it to fix any problems at any stage.

It’s a great little amp, considering its size.