Wednesday, December 10, 2008

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:

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.

Thursday, November 20, 2008

My first ever electric guitar

Back when I was about 17 (so let’s guess 1987) I got my first electric guitar. I already had an acoustic, but it was time to move on to more exciting things. This one came courtesy of a friend of my brother’s, and cost me (if I remember right) either £40 or possibly £60. It had a red finish, with just a hint of orange, black pick guard, two chrome covered pickups with “Hofner” written on them and a maple neck with rosewood fingerboard. There was no name written on the head of the guitar, so I assumed it was rubbish, although I remember it played great and had a real ‘60s rock and roll tone to it.

At the time though, what I REALLY wanted was a nice red Strat, and I wasn’t too keen on that far-too-much-of-a-hint-of-orange finish on my no-name, so I sanded the body down (very badly) and resprayed it black (also very badly). I changed the old-fashioned-looking knobs to some modern black plastic things and painted the head black too. I also changed the tuners to black Gotoh-type things. After a year or so, I sold it to a school friend and forgot about it for a few years.

I thought about it a few times years later and tried to find out what sort of guitar it was, but had hardly any information to go on. Going on the shape alone, I simply couldn’t find the same guitar anywhere, even on Google, so gave up on ever finding out what it was. I also tried pretty hard to get back in touch with the guy I sold it to, in the hope that he would still have it and would be willing to sell it to me, but without success.

Forward wind to about 2005 and I found myself co-incidentally having a chat with the guy who sold that same guitar to my brother’s friend (before I got my hands on it). He told me a little more history. It seemed that the guy who had had it before HIM had stripped it down and resprayed it (very well, I might add). It was in fact a Hofner guitar, but the logo had been removed during the sanding process. This was enough info to really start my search.

It wasn’t very easy (due to limited production dates of this exact model), but I finally found out that it was a Hofner Colorama II, made in 1963. The final confirmation came courtesy of this page:
If you ever need to find out anything about old Hofner guitars, then I can’t recommend that site enough.

With this new-found knowledge, I just couldn’t stop myself from searching for one for sale. Finally, about a year later, I found one exactly the same (including the colour) on ebay and managed to stick in a cheeky last-minute bid, winning it for something like £130. It is fairly bashed up, but nothing that can’t be restored. Here are the photos from the ebay auction.

The moment I won the auction, I felt like I had corrected the 20-year-old mistake I had made when I sold my first ever electric guitar.

I will need to respray this at some stage, but that's fine. As far as replacing the hardware goes, well, I need to restore the machine heads to a vintage style. At some stage someone upgraded these to Gotoh-type tuners (I hardly have the right to criticise that, hehe), and I need to replace three of the knobs (two volume knobs and one tone knob), as they have lost their metallic labels, which can't be bought separately unfortunately.

I managed to find one volume and one tone knob on ebay from a similarly-aged Hofner, and here's the best bit; I still have one of the knobs I took off my old Hofner 20 years ago. I also bought a set of vintage-looking Kluson tuners, that will look very close to the originals, but will work much better than they ever did.

Here are the tuners and the knobs I bought:

Just one small problem though. The guitar is in storage at my brother's house in Ireland and I'm in Taiwan, so the restoration will have to wait.

Sunday, November 2, 2008

The Mystery Box

A while back, I went to check out Tony's music shop in Taipei and noticed that they had this obviously home-made guitar pedal in the display case.

It was priced at NT$600nt (about US$20), and I was pretty much willing to pay that just for the parts I could use out of it.Anyway, I asked if I could try it out and they let me. It sounded superb.

There are two main amplifying components on it, a little 8-pin chip and a transistor.

The chip is marked:

And the transistor is marked:
C550B (This appears to be a BC550B)

There are three controls on it, labelled volume, tone and gain.
There are two toggle switches. The one on the side is a 3-way, with capacitors in 2 of the positions. It works as a tone filter I guess. At the back is a two-way switch, which appears to work as a kind of turbo overdrive.

Pot values are as follows:

TONE - B100K
GAIN - A50K (dual gang)

(A=audio taper, B=linear taper)

I traced the path of the dual-gang gain control. One gang connects between pins 1 and 2 of the OP275 and the other gang goes between pins 6 and 7 of the OP275. Shown below is an OP275. You can see that the gain control boosts BOTH amplifying stages at the same time. Serious boost there.

The circuit appears to be something between a Big Muff Pi and a Rat, and despite requests on 3 different sites for information, it appears to be a totally unique design. If you know otherwise, please do let me know.

Here's a couple of pics of the guts:

incidentally, they dropped the price to NT$500 while I was paying for it. Happy days.

Monday, September 8, 2008

The Volumizer!

Today I’d like to show you the booster pedal I made. It’s a straight clone of an MXR Microamp. The Microamp is a great booster pedal because it simply adds volume. You can use this to just increase the volume of your guitar for solos, or you can use it to overdrive your amp. The choice is yours.

The circuit diagram for the Microamp can be found at General Guitar Gadgets asks that other people don’t post their circuits elsewhere, so I won’t. Just go to this page to get it: (click on “microamp schematic”).

The circuit is pretty simple, using a single TL061 as the amplifier. You can buy a ready-made PCB from General Guitar Gadgets, which would make life a lot easier, but I decided I would just build it on veroboard (strip board) since it was a pretty simple circuit. If this is your first time building a circuit, then just buy the PCB. You won’t regret it.

I made a quick veroboard sketch of the circuit (yes I know, it's rough, but it's been confirmed as accurate).

Anyway, here are a couple of pictures of the circuit during construction.

At first I built this into a much bigger enclosure, but then I decided to try to fit it into a much smaller box. To achieve this, I had to squeeze the components a little bit closer together on the veroboard and then cut a bit off the board itself, as you can see in the following photo.

It’s a really tight fit, but there’s just enough space to add a 9v battery (though I doubt I’ll do that).

I then added a bit of insulation to make sure the circuit board didn’t make contact with the metal enclosure.

I see a lot of people making their own stomp boxes, and doing a really good job, but then just leaving the box unpainted, or painted a single colour with no writing, or something scrawled on it like a child had done it. I figured I had done all this work on the electronics, so why not try and make the box look nice too? So, I painted the box black, then drew something up on the computer and printed it out on photographic paper (one side is sticky). I didn’t want to rip off the Microamp name, so I called it the Volumizer.

Here you can see it next to a standard-sized pedal (a Digitech DigiDelay) for size comparison. Just in case it’s not clear, the Volumizer is the smaller pedal.

Sunday, August 17, 2008

Two-channel passive mini-mixer

Hello all,
Well, I didn't want to just stop after posting about the guitar. I have been known to dabble in other little projects after all. So don't be surprised if those other projects make it on here for time to time.
Today I'd like to show you the little two-channel passive mixer I made. I needed something that would let me plug two guitars into the same amplifier (and both be used at the same time). So, if someone were to come round to my house, we could both plug a guitar into the same amp. You can't just use a y-connector, since that's just amateur, and changing the volume on one guitar would affect the other. I'm pretty sure it could be unhealthy for certain amps too. Also, I wanted to be able to adjust the level of each guitar so that if one were more powerful than the other, this could be balanced out. Lastly, I wanted to make it as portable as possible, so that I could even stick it in my guitar case.
So, I searched for the simplest two-channel or multi-channel mixer schematics I could find and then came up with this:

Note that I don't claim to be the inventor of that circuit. Five minutes on Google and I'm sure you'll find a similar circuit posted on other sites. I have, however, drawn a nice clear circuit diagram for your convenience.

As you can see, the circuit is incredibly simple. Just three quarter-inch jack sockets, two 10k logarithmic pots, two 10k resistors and a box to stick them in (see notes just below).

NOTE: I've noticed several forums pointing to this post, and a lot of debate about the 10k values of both the pots and resistors as being too low (it has been suggested that 500k or even 1M pots would be better, for example). I've used this mixer a lot, as has a friend of mine who I made one for, and both of us have found that it does a perfectly good job, especially at home. My advice is to just give it a go and see how it works for you, rather that wasting too much time in advance theorising about how it might sound. If you find that it doesn't sound good to you, then by all means try different pot/resistor values, and report back in the comments below.

NOTE 2: See the comments at the bottom of this post for more discussion about this. 250Kohm pots and resistors seems to be a good choice by the looks of it.

I couldn't find a suitably-sized metal enclosure at the time of making this, so I settled on a plastic box with a metal bottom. My thinking was that I could always line it with tin foil (aluminum foil) if it picked up interference, but to be honest, it has never been an issue.
Here's a pic of how it looks inside:

And a closer pic of the resistors, etc.:

As you can see, it only just fitted in there. It may have been a better idea to put the two input jacks to the outside of the pots, but to be honest, I don't think it matters either way.
So, here's how it looks from the outside (front and back):

I've been able to use this little device on a few occasions, and it's been fantastic. The fact that it can fit into your pocket makes it incredibly handy too.
I haven't been in this position yet, but it could even save your ass if you were at a small venue with another guitarist and one of the amps stopped working.
And the cost? Pfft... maybe 200 Taiwanese dollars, which works out at about US$6.

Also, just one more comment from me - I ended up re-boxing this mixer. I never had any problem with interference, but I decided to re-box it in an aluminium enclosure anyway, since I found a size that was just perfect, and I liked the idea of it being more robust. Here's the re-boxed mixer:

Wednesday, July 2, 2008

Some more pics of the finished guitar

Well, I got asked if I could put up some more pictures of the finished guitar (and specifically the neck joint), so here's what I've got (apologies for the dust). I thought I had a pic of the wiring too, but I can't seem to find it. Next time I change the strings I'll remove the scratchplate and take some.


(EDIT: The wiring pics have now been added below)


And the wiring pics...

Monday, June 2, 2008

Putting it all together

Well, considering I had already put everything together before lacquering, this step was dead easy. In fact, the hardest part was having the patience to wait for the lacquer to totally dry. I’d recommend waiting several days, or even a week or two if you can bear it.

Be very, VERY careful with screws, screwdrivers, or any other item which might scratch your nice new finish.

It was a wonderful experience making this guitar myself. I highly recommend it. You’ll learn a lot and you’ll get an amazing feeling of self-satisfaction when you put the whole thing together and play it.

You should also take some time to set the guitar up right. Intonation, string height and neck tension will all make a huge difference to how your guitar plays. If you can’t set it up yourself, then consider taking it to your local guitar shop and paying a small fee for them to do it. I recommend learning to do it yourself though, but do be patient. It’s a learning process, so don’t expect to get it right first time.

Here are a few more pics of the finished guitar from various angles. Enjoy.

Please feel free to leave any comments or questions. I’ll be happy to reply.

Monday, May 26, 2008

Finishing the neck

It can be a frustrating time waiting for the lacquer to dry on your cool new guitar body, so this is the perfect time to do some work on the neck.

If you buy the neck (which I did), then there is very little work to do really, other than finishing it off. In fact, here is a list of work you will need to do:

1. Make sure that the machine heads fit in the holes, and if not, enlarge the holes (remember to remove the machine heads after making sure they fit).
2. Do any final sanding, etc.
3. Apply any decals/transfers to the head.
4. Lacquer the front of the head.
5. Lacquer the back and sides of the head and the neck.
6. Fit machine heads, string retainers and a nut.

At the top of this post, you can see a picture of the neck after applying decals and a few layers of lacquer. The packs of letters I used for the logo are there too. They're just standard Letraset (although the brand I used is actually called "DECAdry"). This neck has a rosewood fretboard, which does not require lacquering, so it needs to be masked off. After this stage, the masking paper is removed totally and the neck is then laid face down while lacquer is applied to the back and sides. I found that this method worked really well.

Here is a nice picture of the head of the guitar after all the hardware had been added. I'm pretty happy with it. My surname is Morrow, so I tried to play with this word a little. The upside-down R means that whatever way up the logo is, it looks the same. It's very satisfying to be able to put your own name on the head of a guitar, I have to say.

Friday, May 16, 2008

The finish (part two)

Before you spray your guitar, you should really apply some sort of sealant, otherwise the lacquer (or whatever) will get sucked into the wood like you wouldn't believe. This will make life much more difficult for you and can even affect the tone.
So after applying some stain, that's what I did. Just one layer of sealing varnish, followed by a bit of light sanding.

Next, it was a case of applying layer after layer of spray-on lacquer. This will probably take longer than you think. I lost count of the number of layers I added, and this was probably due to my not applying the sealing varnish correctly. The wood just kept sucking that lacquer in.

Every few layers, you should do some very light wet sanding to try to keep the surface as perfect as possible. If you manage to remove some of the stain by accident, just re-apply it. It's actually not as serious a problem as you might think (or at least it wasn't in my case).

Here's a picture of the guitar with several layers of lacquer applied (as well as some preparation work for the electrics installation, which I'll discuss later):

Even after many, many layers, you can see how the wood is sucking that lacquer. After this photo, I removed the metal parts and kept going with the lacquer until I managed to get a nice smooth finish.

Here are a couple of pictures of the body after the lacquering was completely finished: