Archive for Otalgia FX – Misc Projects

Wah Fuzz !

I had never been happy with my Morley PWV Wah Pedal, no matter what I did to it the Wah effect was never bright enough for my liking , so rather than mod the tone circuit I thought I’d incorporate a Fuzz Circuit inside instead.  Rather than build the circuit from Scratch I bought a pre-made PCB from Poodles Pedal shop and got to work!

The pedal before the work, A bog standard Morley PWV, nice solid metal treddle wah.

The first thing I did was to remove the level control potentiometer (it was soldered directly onto the Wah’s PCB and run three wires to a replacement pot). I then drilled a new hole to accomodate the new potentiometer.  I wanted to turn the fuzz on and off via footswitch so I widened the hole left by the old level control and inserted the new switch in its place –




The next stage was to clear space to insert the Fuzz PCB.

The best place for this was at the top of the pedal so I needed to remove a top section of the PC to create.  After studying the PCB to make sure that I wasn’t going to kill the existing circuit I took about it with a hacksaw and chopped a segment away from the top!


There was no going back!

At this stage I though it was a good idea to make sure that the Wah pedal still worked!  I plugged it an and…. deadly silence. Crap! I had a look at the bit I’d cut out and it was mainly a chunk of copper, earth/grounding.  I guessed that the right hand side of the board was no longe connected to the left. Fortunately the Wah PCB has lots of unused solder pads spare to I simply soldered an earth wire from the right to the left of the board and BINGO! wah was working again.

Next thing was to mark out where the holes needed to be drilled to accomodate the fuzz pots.  I did this with a crudely made paper template, a hole punh and hand drill –



Holes were drilled and Fuzz PCB put into place, perfect fit –



With Fuzz PCB in place the next thing was wire up the new footswitch –


I wanted to use the existing output Jack Socket so needed to insert the Fuzz circuit between the output of the wah circuit and the output jack socket.  Luckily I traced the route of the output socket on the pcb to a point where a jumper connecter bridged across the PCB. This was a perfect place to snip the connection and run wires to and from the new switch to the fuzz circuit.

All the switch wires were connected to the new fuzz pcb and eart sockets and all that was left to do was drill a new hole to place an LED indicator for the fuzz circuit –


All nuts and bolts were tightened, re-assembly of the casing and job done!



The final product –


Notes –

There is little clearance between the wah PCB and casing. Sawing off the top of the board also meant sawing off a little rubber standoff that stopped the board touching the casing.  I used a piece of non conductive foam between case and PCB to prevent any shorts.   Also this mod leaves the circuit side of the fuzz pcb exposed when you remove the battery cover, I consider this pedal mains only from now on!

Videos to follow……..









A Diddley Bo For Pipeman

Pipeman (Jason Stickler) is an old friend and band member.  He turned up at my house on his birthday brandishing a Plank of wood with a pick up screwed to it and a fat E string hanging from a nail.  “Build me a Diddley” Bo he said…… how could I refuse .. it was his birthday 🙂  This is how it looked before the build started ….

Diddley Bo at start of Project

The first thing to add was a tuner key.  This would have to be side mounted so the tune key could be used.  Luckily I had a tuner key left over from the disastrous guitar amp conversion (detailed elsewhere on the site), so a simple drill through and a couple of screws and the tuner was in place.

Tuner for Diddley Bow

Tuner for Diddley Bow (Top view)

Tuner for Diddley Bow (Top view)

Being cheap plastic, the Tuner head snapped off straight away meaning pliers were needed to tighten the string.

Next up was making the bridge.  Unfortunately the only bottles that I had (bottles are traditionally used for Diddley bow bridges) were wine bottles and a little too big, so I needed something else.  A rummage through an old box and I discovered a metal support bracket used for hanging blinds.  This would proved ideal as it was just the right height.  I hacksawed a small groove into the metal to stop the string slipping and then attached it to the plank.

Diddley bow bridge

Diddley bow bridge

One advantage of the bridge was that it was very springy, and could be pushed with your finger to add a whammy bar effect! Nice!

With the string in place and tuned to low C, I then set aboult wiring up the pickup to a guitar jack socket.  The socket Pipeman had given me wasn’t really suitable as it was an open socket and impossible to mount, so I used a socket that I had salvaged from a smashed up car boot sale stereo. I soldered the wires together, screwed the socket to the back of the board and then added some heat shrink tubing to protect the wires.

Jack socket

Jack socket

I plugged it in and everything sounded good.

The final step was to play some notes and mark the plank with relative fret positions. Optional, but makes playing a lot easier!

Fret markings

Fret markings


And here is the finished article, had to drink the wine first though!



Guitar Preamp

The challenge – Take a friends childrens guitar (picture below) with a relatively quiet output and beef it up (in a veggie way) to create a neighbour annoying monster!

Jasons Childrens Bontempi Guitar be being Otalgia modifiedMy initial idea was to rip out the existing amp circuit and replace it with a new louder circuit.  This would be a lot of work, so plan 2 was to add a secondary amp that I could piggy back onto the existing circuit.  There was little free space in the back of the guitar to add new electronics, so the new amp circuit would have to be small …

I decided on using a LM386 amp chip (as used in the smokey amp and countless other mini amp circuits).  A simple amp circuit would only require 2 addtional 47uf 16v Capacitors and would be an ideal size.  The chip is also capable of running off 9v, so hopefully it could share the guitars existing battery power supply. I think this amp is a good choice, as if the circuit couldn’t be piggy backed on the existing circuit then it could also be used on its own.

Their are several variants of the LM386 on the market , all with varying wattage and power supply range (I plan to do an article on the 386 range at a later date).

For this project I chose a 1W version and decided I would incorporate a socket into my circuit so that the chip could be changed if required.

Here is the circuit showing the pinouts of the chip (quickly drawn for the purpose of this blog!) –

sketch of 386 amp

You can see from my illustration that pins number 1 and 8 have been connected together.  These 2 pins control gain stage, so connecting them together will ensure the chip has maximum output – lovely!

The circuit needs to be small so I have decided to use veroboard (strip board). Veroboard is board that has rows of holes and horizontal strips of copper and is ideal for quick circuit construction.  To design a compact circuit for the stripboard I have decided to use a great bit of freeware called DIY Layout Creator ( ).

The result was this –

Layout for LM386 amp by Otalgia










On the layout you can see that there are red squares with circles inside.  These indicate places in the circuit where the copper tracks on the vero board must be removed.  This can be done with a dedicated bradle or by using the end of a drill bit and giving a few twists.

You can also see that a few items share holes in the vero (the capacitors in particular).  This placement is as a rule not recommended, however I did this so that I could keep the circuit size to a minimum.

With the copper track breaks completed, the veroboard is now ready for the components to be soldered to (see pic below).  The picture below shows the copper track side of the board and is a reverse layout to the one above (as the components are mounted on the plain non-copper tracked side of the veroboard.

Unpopulated veroboard for LM386 amp




About 30 minutes later, lots of cursing and a few solder burns and the circuit is built. Note the grey heat shrink tubing on either side, to give the wires a bit of extra support –


Assembled 386 amp built by Otalgia FX



With the circuit built, a quick test of the circuit was set up using lots of crocodile clips and a spare speaker – sounds good!

LM386 test circuit for Otalgia preamp project



Removing the back panel from the guitar revealed little space to add the new circuit so the old electronics were removed, leaving only the speaker wires, battery connection and pickup wires remaining.


Inside wiring of childrens guitar


The new amplifier was wired into place and the power turned on….. DISASTER!!!

A piercing shrill noise that sent the dogs running down the street and made grown men cry emitted from the speaker.  Suddenly it all made sense.. why had the guitar been so quiet in the first place … it was now obvious … if you put a pickup up next to a loud amplifier speaker it feeds back …. EPIC FAIL, project over!!!!!!