I was fascinated by gmoon's design for a super-simple guitar pedal, the ValveLiTzer, that used a tube as the heart of the effect. Unfortunately I don't play guitar myself, so I built one for my friend's birthday instead. Here are the results of my design. The circuitry is virtually the same, but the case is much different.
To build my version of the ValveLiTzer, you will need everything listed in gmoon's instructable. I bought nearly everything at Antique Electronics Supply, except for the LEDs (eBay), resistors and capacitors (local electronics shop), and wire.
EDIT: Be sure to check out an alternate version of this design, which I call the ValveLiTzer Trifecta. Same circuit, very different case!
1 12FQ8 tube
1 9 pin miniature socket
2 1/4" mono jacks
1 50k linear potentiometer
1 500k audio (logarithmic) potentiometer
1 SPDT (on/on) footswitch
2 blue LEDs
2 1000uF 25V electrolytic capacitors
2 1Mohm resistors
1 470k resistor
1 220k resistor
1 47k resistor
2 470 ohm resistors (for LEDs)
2 0.01 uF capacitors
1 0.1 uF capacitor
24 AWG stranded wire
about 2 square feet of 17mm thick Russian Birch Plywood (aka Baltic Birch)
about 1 square foot of 2-3mm thick plexiglass, Lexan, or polycarbonate plastic sheet
about 1 square foot of 3mm thick aluminum or brass plate
7 3/4" countersunk wood screws
some rubber stick-on feet
wood stain (your choice of colour, I used "Cabernet" red oil-based stain)
wood finish (I used Minwax Polycrylic water-based finish)
A band saw
A scroll saw
A drill press
A belt sander (or a sanding belt for the band saw) - optional, though good to have!
A Dremel tool with a drill press attachment
A 1/8" milling bit for the Dremel
A polishing bit for the Dremel
200 and 320 grit sandpaper
a 1/2" wide paint brush
A 1/2" wood chisel
assorted drill bits
and countersink bit - optional, you could also use a 3/8" drill bit
A variable output (up to 12V) DC power supply capable of 3 amps
a piece of scrap aluminum
a tub large enough to hold the cut aluminum pieces
a clothes iron
a laser printer
a sheet or two of glossy photo paper
Step 1: The Case
I decided to craft a very unique case for this pedal. It is roughly in the shape of a figure-8, with the single valve emphasized at the top. The case itself is made of two layers of 17mm thick Russian birch plywood - a very special sort of ply with 13 layers. Its side profile is unique and very attractive (IMO).
Plates of aluminum are set into the top, providing a strong stable surface to mount the switches, jacks and pots. The aluminum is etched with the names of the various components.
The bottom of the pedal is made of diffused (sanded) polycarbonate plastic, which is illuminated from the inside by two LEDs.
I started by drawing the case in Adobe Illustrator. Using the diameter of the valve as a starting point, I drew circles and arcs accordingly until I came up with the design below. There are a few concentric cutouts visible, that indicate the various profiles of the pieces. I also marked the locations of the various components that would be mounted on top.
I then worked out a separate template for the text that would eventually be etched onto the aluminum. I picked a font that matched the aesthetic of the case - you can use virtually any font in the world using the etching method!
Step 2: Cut and Mill the Wood Case
Start by cutting out two rectangles that are larger than the outline of the case from the Russian birch. Cut out a similar rectangle from the polycarbonate plastic.
Glue the two pieces of wood together using carpenter's glue, and clamp them together for a good joint.
When the glue is dry (wait a day for good measure), spray the back of the pattern with spray-on adhesive, wait a minute or two, and stick it onto the wood (waiting a bit allows for easier removal of the pattern later on.) Securely tape the plastic onto the wood piece with masking tape, over top of the pattern.
**Note that in the pictures I show the paper pattern glued to the wood, and the plastic being cut separately. This works too, but you can save yourself some effort by cutting everything at once!**
On a bandsaw or scroll saw, cut out the pattern being careful to maintain smooth, even lines. You may need to reapply masking tape to the plastic to keep it from sliding around. With the outside perimeter cut out, set the plastic aside for now.
Drill two 1/4" holes inside the cutouts where the aluminum plates will eventually go. On the scroll saw, do the interior cuts making sure you follow the inner line. This cut doesn't have to be too precise, but try to be neat anyway.
Now on to the milling. Start by scoring the pattern on the middle line with an x-acto knife, which defines the edge of the aluminum plate. Peel off just the thin strip - this makes milling easier. I learned this the hard way too.
Load up the milling bit into your Dremel, and mount it in the drill press attachment. The Dremel will be used as a mill, or a top-down router. Set the wood piece with the bit in the middle. You will need to precisely set the depth of the cut - instead of using the lever on the side, I "permanently" set the depth by changing how far up the stand the Dremel was mounted. Set the depth to be equal to the thickness of the aluminum.
Now, spin the Dremel at 20-25,000 rpm and carefully mill out the ledge up to the edge of the paper pattern. To avoid overloading the bit or burning the wood, do multiple passes, each time shaving closer to the line. Periodically check the cutting depth as it may come out of adjustment. Repeat for the smaller valve cutout at the top.
Step 3: Chiseling and Final Millwork
Eventually, wires will need to pass between the main section and the valve section. With the drill press set for a 1/2" cutting depth (that is, a 1/2" deep cut into the material), use a 1/2" drill bit to cut out a valley on the BOTTOM of the wood case, between the large and small sections. Clean up the valley using a chisel.
With a 1/2" drill bit (preferably a Brad Point or Forster, though a regular bit should work), drill a hole into the notch on the side of the wood, where the power plug will eventually go. Work carefully and clamp the workpiece so it won't move - this is a tricky cut.
Step 4: Sanding
Start by sanding the sides. Reattach the plastic bottom to the wood case using masking tape. Sand all around the outside of the case using a vertical belt sander. You will need to reposition the masking tape once or twice to cover everything.
Go over the sides again by hand using 200 grit sandpaper, then 320. Remove the plastic and set it aside again.
Sand the face of the case using 200 grit sandpaper, then 320 and set it aside until you've finished the aluminum plates.
Step 5: Drill, Cut and Polish the Aluminum Plates
If you happen to have a laser cutter capable metal, I encourage you to use it. But if not, here's how to do it with a band saw.
First, prepare the metal by sandwiching it between two sheets of 1/2" plywood. Use masking tape to hold the layers together. Doing this give you something more substantial to hold onto as you cut, and it prevents the buildup of metal burrs on the cut metal edge. Using spray-on adhesive, glue the plate patterns onto the wood.
Before cutting, drill the five component mounting holes on a drill press. Use the appropriate drill bit size for the part in question - the switch, pots and jacks all require different size holes. Drill a pilot hole in the exact center of the mounting hole for the valve (it will be widened later using a step bit).
Install a 15tpi blade on the bandsaw and run it at 3000 fpm. Cut out the main section and the valve section. Make sure you cut on the right line!
With the plates cut out, remove them from the plywood sandwich. Smooth the edges using sandpaper or a file. Test-fit the plates in the wood case - the fit may be tight or not fit at all - if so, keep filing and sanding the metal until it fits perfectly.
The potentiometers have small keys that prevent them from rotating in their holes. Insert a potentiometer into its hole, and mark where the key will be. Ideally, the pins should be pointing towards the middle of the metal plate! Drill the holes with an appropriate sized drill bit.
The valve plate will need a bit more work as well. First, clamp it down and using a step bit, widen the hole to fit the tube socket. Alternatively, you can use a scroll saw with a metal cutting blade. Mark out two mounting holes for the socket and drill those as well. In a vice, clamp down the plate and bend it to a 90 degree angle, to match the notch at the top of the case. Be very careful when you measure the position of the bend, to get a good tight fit.
Once the fit is good for the main and valve plates, you can polish the metal. Using a buffing bit and a dremel (or by hand if you like!), polish the aluminum to the desired luster. Be aware that the more polished it is, the better the stencil transfer will work, so go for a mirror-like finish if you can. Wash off any buffing compound with soap and water, then thoroughly clean the metal with alcohol.
Step 6: Etch the Aluminum Plates
To mark the jack, switch and potentiometer functions I etched the board using electrolysis. The rough, sunken labels contrast nicely with the polished plates. They're also permanent - no amount of use will wear them off.
You will need to construct a simple electrolysis etching tank. There are plenty of Instructables on how to do this, so use one of them if you like.
I used a 2 liter ice cream container filled with warm water and a few tablespoons of table salt (NaCl). Note that if you use regular salt, chlorine gas may be produced during the etching process. Washing soda is a great alternative to table salt and I recommend you use it instead, especially if you have to work indoors. You will need a second plate as well, at least as large as the aluminum plate you'll be etching. It should be made of aluminum.
To power the etching tank, I used a regulated power supply. You can use the same, or you can use a converted computer power supply or a car battery charger. Anything that puts out +12V DC with at least an amp of current will work.
Before etching you'll need to transfer the patterns to the aluminum plates. I used the laser printer on photo paper method. Print the letter stencils in reverse on a laser printer, using glossy photo paper. Make sure the image is good and dark. Cut out the stencils with a 1/4" margin, and write the stencil name on the back of each piece to help keep track of them.
*** If the text doesn't show up properly, you'll need to install the font I used: Blue Stone
Lay out the aluminum plate on a heat-resistant surface, and place the stencils in the correct positions. Now, with an iron set about medium-high with NO STEAM, fuse the stencils onto the metal. Note that as the metal gets hot, the other stencils that you haven't touched yet will want to fuse to the metal all on their own. Either prevent them from moving, or do just one at a time.
The stencils should transfer completely, with no toner left on the photo paper. It took me a few tries to get it right. You can touch up small errors with nail polish (yes, really) but for big mistakes you'll have to scrub off the toner and do it again.
The last step before etching is to cover up the rest of the plate, so that it won't etch. I used packing tape to cover every surface - front and back - that I didn't want to etch. Leave a small unexposed corner at the top to clip an alligator clip onto.
This process is different than electrolytic rust removal. In this case, attach the red (+12V) lead to the plate being etched, and the black (ground) to the second plate. With everything hooked up, turn on the power. This process takes just a few minutes. Soon the water will start to get hot and bubble like a witch's cauldron. Remove the plate every minute or so to check on the etching.
When you're satisfied with the amount of etch, turn off the power, wash the aluminum plate in water, and peel off the packing tape. Then, scrub off the toner with rubbing alcohol. It takes a bit of elbow grease to get it off!
Step 7: Stain and Finish the Wood
Prior to installing the metal plates, you'll want to stain and finish the woof frame.
I used a nice red cabernet oil-based stain, and an acrylic finish.
Apply the stain with a bristle or foam brush. Apply enough coats to get the colour you want. In my case, I used two coats on the top and three on the sides, since the cut edges absorb more stain. Allow 24 hours for the final coat of stain to dry.
Apply the finish with a bristle brush. The first coat should be very light. It soaks into the wood and really has no effect. Once dry, sand lightly and apply a second coat. Now it'll start to shine. Sand again once it's dry. The third coat will really make it look good. Once it's dry, you're done with the finish!
Step 8: Glue in the Aluminum Plates, and Mount the Components
To glue in the plates you'll need something that sticks well to metal and wood. I used JB Weld, though regular epoxy should work OK too.
Apply the glue to the milled section of the wood frame, and stick down the metal plate. Before sticking down the valve plate, insert the valve socket and power jack with wires pre-soldered to the pins. Otherwise it will be extremely difficult to put them in after.
Once the glue is dry, you can mount the various components. Use the hardware supplied with the parts to secure them in place. Don't put the tube in just yet, it'll just get in the way.
Step 9: Wiring
Are you handy with a soldering iron? Good! This will only be somewhat tricky.
I used no perf board or circuit board. Instead, I just soldered components in the most efficient positions, making sure not to cross any wires. Follow the schematic and solder every part in place. Use wires cut to length where necessary. I used 24 AWG teflon coated wire, it's very nice to use.
In addition to the original schematic, I added a few parts of my own. I soldered two 1000uF electrolytic capacitors from power to ground, to help filter the power supply. I also added two bright blue LEDs with current limiting resistors. The LEDs cause the case to glow from the bottom.
Triple-check your wiring, then plug it in without the tube installed. The LEDs should glow. If they don't, you made a mistake. Go in and fix it. Once you're satisfied, plug in the tube and turn it on. The tube should glow faintly.
Step 10: Testing
Now you can test out the pedal!
Plug your guitar into the IN jack, and your amp to the OUT jack. Go ahead - pluck a string. See how it sounds. Test the bypass switch to make sure it actually does something. Tweak the volume (Boost) to make sure it works. Turn the drive (Dirt) and listen to the distortion increase.
The effect is more subtle than some other pedals, but it's there.
Also listen for noise. There should be very little. If it's very noisy, there's probably a grounding problem. Some things that may help include using a switching power supply instead of a transformer power supply (a small wall wart instead if a big one), and grounding the metal plates to the ground on the power supply.
Once you've verified that it works, you can go to the next step...
*** Thanks to my friend for sending pics of the pedal set up with his guitar and amp! ***
Step 11: Attach the Base Plate
With the pedal working you can attach the plastic base plate.
If you haven't already, frost one side of the plastic by sanding it with 150 or 200 grit sandpaper. Get it as even as you can.
Lay the base onto the bottom of the frame, and mark out locations for the screws. I used 7 flat-head wood screws placed in strategic locations.
Drill out the holes using the correct bit for the size of screw you have. Then, countersink the holes on the shiny side of the plastic. Be very careful, the plastic is thin and it's very easy to drive the countersink straight through the plastic!
With the holes drilled, reposition the plastic plate onto the base and screw it in place.
Add rubber feet to the base to prevent the pedal from sliding around.
And that's it! Have fun and be sure to show off to all your envious friends. ;)