The Noisy Cricket Guitar Amp

The Les Paul DIY guitar project is nearing completion. Only a few more coats of Tru-Oil, and then assembly, wiring, stringing, tuning and intonation are necessary. Oh, wait...

What I really meant to say is that I want a small guitar amp that I can take anywhere. When googling "simple diy guitar amp" you'll quickly come across the Noisy Cricket Guitar Amp, the latest of a series of LM386-based mini amplifiers like the Ruby amp, Little Gem and Smokey Amp. It is a simple amplifier running off of a 9V supply (wall wart or battery) and consisting of a handful of components around a LM386 audio amplifier chip.

You can find various veroboard designs for a Noisy Cricket on the intertubes, but I chose a small protoboard to build mine. Here's a picture of the component layout. I usually do small layouts in Microsoft PowerPoint. No, I'm fine.

Veroboard panel. Note pinout difference between MPF102 and 2N5951.

I ordered all the components at Futurlec, especially the LM386 that I don't have at hand. It's one of the cheapest supplier, but they ship from Hong Kong which takes at least three weeks. The speaker is a small 10cm Visaton full range speaker (FR 10 HM) from Conrad at less than CHF 15, including shipping.

The build follows closely the guide on DIY Strat with the following exceptions: instead of a separate power switch I'm using a potentiometer with switch for the volume control. I also had to use a 2N5951 JFET instead of the original MPF102, and finally, I'm going for an integrated amp and speaker design.

Noisy Cricket parts

I soldered the board according to the layout above. The picture below shows the result (LM386 not in place yet). Note that the board is not a stripboard. Therefore the connections have to be made by bending and soldering the component leads appropriately. Apart from the two gain connections on pins 1 and 8 of the LM386, no additional wires were necessary to complete the circuit.

The leads that stick out on either side indicate the connection points for the potentiometers, switches, and power as indicated on the layout above.

Panel wiring in progress.

In the meantime I brought my (limited) wood working skills to fruition and built a wooden cabinet for the amplifier. As usual, the corners are nearly but not completely at right angles, but thanks to modern photography it can all be blamed on visual perspective.

Raw amplifier cabinet, sanded and ready for staining.

I then stained the box using a water based mahogany stain, and after it had dried completely, I applied 3 layers of Tru-Oil, giving it a nice vintage look that goes very well with my shoddy wood work.

Stained and oil-finished cabinet, surrounded by a glow of contentment.

I also finished the panel wiring, and the amplifier is now more or less ready for final assembly. The following picture shows the completed panel. From left to right we have volume control with power switch, tone control, grit, gain control, and bass switch. The protoboard is attached to the back of the panel using an aluminium carrier that is held in place by the grit switch. I soldered a 4 pin connector (Vcc, Ground, Input, Output) to the board to allow for easy assembly/disassembly.

The connector plugs into a 4 pin header that is part of the back panel, where the input, headphones, and power jacks are located (see last picture). There's also a 2 pin header there for the actual speaker.

After having fixed a small problem with the protoboard (I had forgotten the connection between pins 3 and 4 of the LM386; see design above), the amp worked! YES!!! It won't fill a concert hall, but as an exercise amp for the living room, it'll do just fine.

The controls have less effect than I expected, something I have to check, but at least I get some sound through the speaker. The connectors have already paid off, because now I can disassemble, check, fix, and then reassemble everything. For now, I have assembled everything and made a few pictures.

Finished guitar amp. I'll look for a speaker grille later.

Back of amp with power, headphones, and input jacks.

This more or less completes the construction of the Noisy Cricket Guitar Amp. I'll check the tone, grit and tone controls to see, if I did everything right, but for now I'm quite satisfied.

I'm aware that you can get a Marshall Micro Amp for around 50 Dollars, but to be honest, building the Noisy Cricket was way more fun than making an online order.

RAM Cartridge for the Yamaha DX7 Synthesizer (Part III: Testing)

DX7 RAM cartridge version 1 (left) and 2 (right). Surprisingly(?) neither works.

My DIY project to build my own RAM cartridge for the Yamaha DX7 digital synthesizer is currently in limbo. I have fixed everything that I found to have made wrong with my prototype board, and it still does not work. I had the following problems with my board:

• Edge connector is too narrow. It appears to have a 3+ mm pitch. Mine has a tenth inch (2.54mm) pitch. I fixed it by gluing a separate correctly sized/pitched double sided  PCB to the board. At the same time I also fixed...
• Swapped connectors. There was a 50-50 chance as to which side of the edge connector faces which way. My guess was wrong: the side with the power supply faces backwards. To fix that, I had to wire the pins of my glued-on PCP to the corresponding pins on the prototype PCB crosswise back-to front and front-to-back.
• Missing pull-up resistors. For a reason that totally eludes me, I forgot to add pull-up resistors for address lines 8 to 10. I soldered them at the back of the PCP using the power pin on a near resistor network.
• Missing 2.2uF/16 polar bypass capacitor. I know from various synth DIY projects that you're supposed to add bypass capacitors near the power supply of ICs. I didn't add one on the prototype board, because the design on yates.ca doesn't include one either.

Despite all of the above, the board fails consistently with a Write Error! message. I can briefly see the message Under Writing flash by, which led me to the missing address pull-up resistors. That didn't fix it, though. I'm a bit at a loss, because the circuit isn't that complicated, and I can see no reason why it shouldn't work. Perhaps I have simply fried the 28C64 EEPROM? It is a surface mount device, and I'm not the most expert solderer. For me, it means to go back to the drawing board.

In the meantime, you might be interested in the DX7 RAM Cartridge project by blogger Brian Durocher.

RAM Cartridge for the Yamaha DX7 Synthesizer (Part II: Prototyping)

You knew it! If you followed my Les Paul DIY build log, you're not surprised to hear that I managed to bungle the DX7 cartridge project in a similarly spectacular fashion, and it's all my fault.

The prototype boards arrived, and they look awesome! The PCB material is of a dark violet color, and all the solder pads are golden. I ordered them at OSH Park, where you'll always get (multiples of) 3 boards.

DX7 cartridge prototype boards, rightmost already populated.

When I checked them I saw instantly that I made the connector part too small. Instead of measuring the proper connector spacing, I violated Sommerer's Law ("your assumptions are wrong") and assumed them to be the usual one tenth of an inch or 2.54mm. Well, its closer to 3 mm, so they don't fit. Oh, well!

Now, instead of throwing them away and order another batch with the proper dimensions, I'll use them as tinkering material. I already ordered a small sheet of blank double sided circuit board, which I'll cut to size using a high-tech template that I made from an obsolete phone card.

I'll make the properly spaced connector traces by filing or scratching gaps into the copper layer, and then glue the contraption as a new connector onto the PCB. All that's needed then is pieces of wire connecting the pads on the cartridge PCB with the corresponding pads on the new connector. It'll look hideous, but serve its purpose.

But first I have to wait for the blank PCB to arrive.

Les Paul DIY kit (Part VII: Epilogue)

This is the seventh and final part of my DIY Les Paul kit build report. I strung the guitar and tuned it by ear using a guitar sound on my Yamaha MOX digital synthesizer. It appears that the neck is still reacting to the tension caused by the strings, because I needed several tuning cycles until the guitar stayed in tune for a while. To my surprise, the guitar does not appear to need a separate intonation step, as I get a clean octave when comparing the base tone to the 12th fret. What I get, however, is string buzz, especially on the bass E string. I'll wait few more days for the neck tension to settle and then check the correct distance of strings to frets. There are countless YouTube instruction videos on that subject, and I'll consult them all. Or so. Anyway, from various guitar sites I learned that it could also be uneven frets, so I'll check that, too, before I start tweaking the neck curvature by meddling with the truss rod. So far, however, I consider the guitar set up and ready to play.

Far more knowledgeable people than I am say that a DIY guitar is an ongoing project, and it'll need your continuous attention. But this report isn't, and therefore I'll end it here. Despite all the setbacks and problems encountered (or self-inflicted), building a guitar from a kit was a valuable experience, and I might possibly attempt to build another one. In the meantime, however, I'd like to thank all of my regular readers (both of them) for their interest. Perhaps you're going to build your own guitar from a kit, and if you do, please leave a note and a link to your own build log.

Les Paul DIY kit (Part VI: Assembly)

This is a rather short part VI of my DIY Les Paul kit build log, because fitting and screwing in the machine heads, mounting the neck to the body, screwing the strap buttons to the body and finally the covers for the cavities was surprisingly quick and painless. I'll let the pictures speak for themselves.

The nearly finished guitar in full glory.

Front of the guitar. Note shiny finish.

Back of the guitar with neck shield, covers, and strap button.

After all the setbacks I had, I must say that it looks way better than I anticipated. I'm quite pleased with the result.

OK, next will be stringing, tuning, and intonation of the guitar. I'll need to check a few YouTube videos to learn how it's done. Until then: stay tuned.

Les Paul DIY kit (Part V: Electronics)

This is part five (finally...) of my Les Paul DIY kit construction diary, and finally, I'm going to assemble the guitar.

After having applied a few more coats of Tru-Oil (in total 16 on body top, 12 on body edge/back, and 8 on the neck), I'm ready for l'assemblage. That's french for la montage which is also french. Before starting, it makes sense to line up all the screws that go with the kit to see what's going where, because the parts list may be inaccurate (it is in my kit), and you want the right screws in the right positions.

I wanted to start with setting the neck. My kit is a bolt-on design, hence more like an Epiphone Les Paul, than a Gibson. The plan was then to continue by hammering in the bridge posts in the pre-drilled holes in the body. But when I inspected the pre-wired electronics contraption I found a ground wire for the bridge that needs to be routed to the post cavity before the post is hammered in (it ends up wedged-in between post and cavity wall). So this kind of prescribed a certain sequence of work: first electronics, then bridge posts (with the ground wire in place), and then the neck.